Signs of Summer 10: To Anthropocene or not to Anthropocene?

Image by C. Khabbat, Wikispace

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One of the things about science that puts many people off is the incredible number of words that you need to learn to be able to talk about (or listen to) scientific ideas. Really bad science teachers, in fact, stress the word aspects of science so much that their students begin to believe that science is just a list of odd (but picky and precise) terms and facts that need to be memorized. I apologize to everyone who has had such an ill-informed and ignorant teacher!

We do need, though, some precision of language and some terms that express ideas beyond our everyday experiences in order to explore many scientific ideas. Words like the terms in the hierarchy of the Geologic Time Scale, for example, allow us see and discuss things that go far beyond days of the week or months of the year. I am sorry, though, for having to introduce so many funny names!

Image by Dragonsflight, Wikimedia Commons

I am writing this on Tuesday, July 24, 2018. This day, like all of my previous days and, I hope, all of my days to come are in the sub-division of Earth’s geologic existence called the Phanerzoic Eon. The Phanerzoic Eon started about 541 million years ago when living organisms “suddenly” became both more complex and more abundant! The Phanerzoic Eon, then, is defined as the span of time when the Earth has abundant plants and animals.

There were three eons before the Phanerzoic: the Hadeon, the Archean, and the Proterozoic Eons. Collectively these three eons are lumped into a phase called the Precambrium Super-eon which spans the first four billion years of the life of the Earth (or, to orient these numbers clearly, the first 90%, or so, of Earth’s existence).

The past 541 million years, this Eon of Life, then, is just a blink of the geologic eye in the span of “Earth time!”

The Phanerzoic Eon, like all eons, is divided up into eras. There are three eras named to express the stage development of life on Earth: Paleozoic (“early life”), Mesozoic (“middle life”) and Cenozoic (“new life”). Tuesday, July 24, 2018, of course, is in the Cenozoic Era (which has been going on for the past 66 million years (ever since something really bad happened to 75% of the species that had dominated the Mesozoic!).

Asteroid impact ending the Mesozoic Era, D.E.Davis, Public Domain

The Cenozoic Era is divided up into three periods: the Paleogene, the Neogene, and the Quaternary. The Quaternary Period is the most recent of these periods and represents the past 2.6 million years. This is the time in which humans (defined as individuals of the genus Homo) have existed. This is also the time of the Ice Ages and the present day “warm” period (which, in fact, may be just a pause in the ice age cycle (we’re not absolutely sure about that)). These two events (Ice Ages and non-Ice Ages) serve as the basis for the two epochs of the Quaternary Period (epochs are, of course, divisions of periods): the Pleistocene (2.5 million years of ice advances and retreats across the face of the globe) and the Holocene (the past 12,000 years, or so, when the Earth has been warm and relatively ice-free (and during which humans developed agriculture and all of our other technologies!).

Alaskan glaciers. Photo by Roger W. Flickr

Epochs, by the way, are divided up into Ages. The 12,000 years of the Quaternary Epoch is divided pretty evenly (about 4000 years each) into three Ages: the Greelandian Age, the Northgrippian Age, and the Meghalayan Age. The onset of the Meghalayan Age began with the global climate shift that led to the end of the great, ancient human civilizations of North Africa, the Mediterranean, the Middle East, India and China.  We, here on July 24, 2018 are in year #4,200 (possibly at the very end!) of the Meghalayan Age.

So what comes next? Is there a new Age in the wings waiting to come into definition?

There was a proposal a few years ago to call the “now” the Homogeocene to emphasize the influence of humans in the homogenization of the distribution of plants all around the world (see Signs of Spring 11, 2017). There have also been proposals to define the “now” in broader terms that emphasize more of the scope and magnitude of the human influence on the land, sea and air systems of the Earth. These proposals are all wrapped up in a geologic term called the Anthropocene.

The Carnegie Museum of Natural History in Pittsburgh has (until Sept. 3, 2018) an exhibition in which the characteristics of the proposed Anthropocene are displayed. Deborah and I had the chance to see this exhibition in May with our friends Patrick and Mardelle Kopnicky.

Photo from Grendz,com

The exhibit illustrated human impacts on coral reefs, on plant flowering and leafing times, on domesticated and wild animals, on extinction rates, on habitats, on climate, and on the composition of the atmosphere itself. The astounding amounts of plastics produced, used, and then discarded into landfills, fresh water systems and the oceans were graphically and visually displayed. The wall-sized photograph of a surfer wrapped up in the curl of a wave that was densely packed with floating plastic debris is an image I cannot get out of my mind. These plastics represent the introduction into the systems of the Earth materials that have never existed before in Nature (see Signs of Fall #4, 2017). Their ultimate impacts on the Earth are still unclear.

The astounding (and growing) number of human beings on Earth (another feature of the Anthropocene) leaves one with the impression that none of the changes can ever be reversed (see Signs of Spring 3, 2016).

So what is the Anthropocene? Its name sounds like an Epoch. Something proposed to replace the Holocene? A committee of the International Commission on Stratigraphy (ICS) has proposed to make the Anthropocene the next geologic Age (i.e. the next subdivision of the Holocene). This proposal must then be voted on by the entire ICS and then approved by the International Union of Geological Science. The Anthropocene would not be a new Epoch (the Holocene still is incredibly new and appropriately defined), but it would be a logical continuation of the Ages of the Holocene emphasizing the prime force that is shaping our planet today: us.



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Signs of Summer 9: Something is Missing

Indigo bunting. Photo by D. Sillman

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It always takes me a long time to notice that something is not where (or when) it should be. I am pretty quick to see new things right when they occur or right when they arrive: the first robin of early spring, the first crocus to flower, the first trill of the spring peepers, the first whirr of the dog-day cicadas, or the first snowflake of winter. But when something that is expected just doesn’t show up it may take weeks for me to note its absence.

A great example of this is the indigo buntings that for years have nested along a specific section of the Roaring Run Trail. Four miles up the trail from the main parking lot there is a fork in the Roaring Run path. The right side of the fork goes down a series of switchbacks and then continues for another mile or so to the parking area at Edmund. I seldom ride my bike down these switchbacks because of the necessity to then ride back up them or, if proceeding on to Edmund  the need to ride up the long, Edmund hill. I do prefer more level grades for my bike riding and nature watching!

The left side of the fork, though, goes off on a flat path for about a hundred yards into the western side of the ravine made by Flat Run creek. The trail stops in a shady turnaround just below the old wooden bridge that used to span Flat Run. You can still see the bridge abutments on either side of the ravine, but the actual crossing span is gone. I remember nervously crossing that bridge years ago on some hikes! It was made up of tarred, heavy, wooden beams. The whole bridge sagged and sighed with each footfall. It is good that that span was removed!

Male and female indigo buntings. Photo by B. Weaver, Wikimedia Commons

There is also, in times of abundant rainfall, a waterfall just north of the turnaround that drops noisily into Flat Run. It is very pleasant to stop and get off your bike when you get to the end of the trail and walk down the short path to look at the rushing water.

Every late spring and summer, all along this left-fork trail, with the exception of last year (2017) and this year (2018), you could reliably see two or three male indigo buntings. As you passed through each bird’s respective territory they would streak out in front of your bicycle or fly up to a series of perches to sing you along the trail. You felt properly watched and knew that your territorial trespasses had been recorded when you biked along this path!  Deborah and I called this stretch of trail “Bunting Alley.”

Indigo buntings are small (about five inches long and a half an ounce in weight) members of the cardinal family of song birds. The males are intensely blue and, since they do nothing with regard to nest building, egg brooding, or nestling feeding, they have a great of time and energy to spend their days flying from high perch to high perch singing their territories and watching out for potential nest predators (or passing bicyclists).

Indigo bunting. Photo by K. Bolton, Wikimedia Commons

I have fifteen years of notes on these “Bunting Alley” birds, and was seldom disappointed when I rode my bike down through their territory. Indigo buntings can have two or even three clutches in a summer season, so the males were present and alert through most of the summer. Last year, though, I saw no indigo buntings here at all, and this year it has taken me until early July to realize that they were not here again!

Indigo bunting populations have declined by about a third since the mid-1960’s. Loss of their over-wintering habitats in Mexico and Central America and increased urban and agricultural land use (leading to the clearing of the shrubland in which these birds prefer to nest) may have contributed to this decline. Their nests are also quite heavily parasitized by cow birds which causes considerable loss of bunting eggs and a great reduction in the numbers of their successful fledgings. Interestingly, indigo buntings are classified as “disturbance dependent” birds. Deforestation and abandonment of farms and, possibly, even strip mining which generally lead to increased growth of shrubby habitats tend to favor populations of buntings.

In some places in the eastern United States, indigo buntings may actually be one of the most abundant song birds! In other places, though,  they are relatively rare.

But, why have they abandoned this stretch of the Roaring Run Trail after all of these years?

The surrounding vegetation along this trail has in recent years become increasingly dominated by Japanese knotweed. Possibly the knotweed has filled in the habitat layer that the buntings prefer. Perhaps the knotweed is not suitable for the buntings to nest in (not sturdy enough for an above the ground nest or not dense and concealing enough for an on-the-ground nest?). Perhaps the knotweed does not support the insect and arachnid populations upon which the buntings rely for food. Perhaps the knotweed has excluded the native plants from which buntings gather the seed and fruit components of their diet. Perhaps the surrounding trees (mostly poplars, cherries and maples) have gotten too tall for the buntings to find suitably located crooks for their nests. The site might have aged past its “bunting stage” and has moved on to more mature forest species (like wood thrushes, perhaps?).

Whatever the reason, “Bunting Alley” is much too quiet these days. The absence of its neon-blue guard-birds is palpable. I did see a goldfinch this morning and enjoyed his bright yellow flash, but he didn’t glare at me like the buntings used to do. He was much too tolerant and accepting.




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Signs of Summer 8: Monarchs!

Photo by D. Sillman

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Over the past month I have seen a number of monarch butterflies (Danaus plexippus) both around my house and up at Harrison Hills Park. The fields at Harrison Hills are loaded with butterfly weed and milkweed and also a great diversity of flowering plants (nectar sources not only for monarchs but for many important insects and birds! Check out Deborah’s website about the wildflowers of Harrison Hills Park ( )). For the past eight years I have also nurtured an expanding patch of milkweed on the east side of my house in the hope that monarchs will find it and lay their eggs on it so that their caterpillars will then use it a food source. I have even “seeded” the plants with monarch caterpillars hatched and raised by Doc and Linda Mueller, but have not had successful chrysalis formations or butterfly emergences. I have seen numerous tussock moth caterpillars on my milkweed (they really chew up the leaves!) but no monarch caterpillars except those few we have introduced.

Monarch Watch (an organization that monitors the yearly surge and retreat of monarchs across North America) reports that the unusual March and April 2018 weather patterns may have had a surprisingly positive impact on the migrating monarchs. While most of the rest of the country (especially the East) was unseasonably cold this March and April, Texas was, as has been the ongoing trend over the past 20 years, unseasonably warm (in fact March 2018 in Texas was 5.3 degrees F warmer than average!). The surrounding cold weather caused the migrating monarchs from Mexico to stay in Texas for longer than usual, and fortunately, they responded with a population boom possibly assisted by the warm temperatures! Although limited by the available milkweed, the Texas monarchs multiplied and then, as the weather in April began to moderate, surged out across the eastern  and midwestern United States.

Monarch migration maps at show a steadily expanding line of migration of the butterflies: In March they were in the southern-most parts of the country, between Texas and Florida, by April they had traveled north to a line roughly between Oklahoma and South Carolina, and by May they had moved up past a line between Kansas and Maryland. By early June they had reached a line that stretched from Iowa to Ohio, and by late June had finally gotten to Pennsylvania, New York and New England.

Female Monarch (photo by K.D.Harrelson (Wikimedia Commons))

The monarchs were reproducing all along the way (so milkweed was critical at each location!). At each stop each mated female laid three to four hundred eggs on the milkweed (spreading her eggs out over a large number of plants), and then the adult monarchs died. The eggs hatched in three to five days depending on the temperature, and the emerging larvae (the “caterpillars”) fed first on their egg capsules and then began to eat the milkweed leaves. They molted five times during their larval life stage and increased their body mass more than two thousand times. The caterpillars take between 9 and 14 days to go through their five instar growth phases.

The monarch eggs and the larvae are under intense predation and parasite pressures. More than ninety percent of the eggs and caterpillars will fail to survive. Eggs are eaten by ants, earwigs and snails, and larvae are eaten by beetles and other insects (like paper wasps) or killed by parasitoid wasps, bacteria, or fungi. Since the larvae feed exclusively on milkweed leaves they accumulate in their body tissues the milkweed’s cardenolides (a cardiac glycoside that can cause the heart of a vertebrate to stop its contractions!). These cardenolides make the larvae (and, eventually, the adults) poisonous to most vertebrates.

The end stage caterpillar then forms a chrysalis within which the tissues and organs of the larvae dissolve and are reformed into the structures of the butterfly. This metamorphosis takes between nine and fifteen days. The adult butterfly then emerges, mates, and continues on its migration and cycle.

Monarch caterpillar (photo by D. Ramsey (Wikimedia Commons))

So at each location, the caterpillars are seen a week or so behind the initial appearance of the arriving adults, and the adults from these caterpillars who then push on northward emerge from their chrysalises about a month later. By late July, migrating adults and caterpillars in many stages of coming and going are all over Western Pennsylvania. It takes anywhere from three to six mating/development cycles for the monarchs to reach the northern edges of their North American range!

Pennsylvania is just one of stops on this seasonal northward surge and eventual southward retreat of monarchs. Some of the adult monarchs that hatch here in mid-summer might, in a typical year, continue on north to lay more eggs on the later developing milkweed in New York and New England. I remember in the early 1980’s seeing clouds of monarchs along the New York State Thruway just west of Syracuse! These butterflies may have had a part of their life cycle tied to the fields of Western Pennsylvania.

Other monarchs that mature here in late summer, though, will turn around and begin the long journey back south. These late summer/early fall born monarchs are part of the overwintering cohort that tries to find their way to the coniferous forests in the mountains of the Mexican states of Michoacán and Mexico. These overwintering monarchs live 8 or 9 months (compared to 2 to 5 week life span of the “summer” monarchs) and will be the individuals that push back north into Texas next February and March where they will mate and lay eggs thus starting the migration cycle all over again!

One of the most accurate ways to access the monarch butterfly population is to count them when they are in their overwintering forests or to measure the area of the forests that have monarchs. In the winter of 1996-1997 18.19 hectares of forest were covered with overwintering monarchs. Last winter, though, there were only 2.48 hectares of forest with monarchs! Monarchs are reaching dangerously low population densities!

Monarch caterpillar getting ready to pupate on a multiflora rose plant. Photo by D. Sillman

Some great local news! Deborah spotted several large (possibly 5th instar) monarch caterpillars on milkweed and multiflora rose plants at Harrison Hills Park! Also, Jane Glenn has reported monarch eggs on her milkweed in New Kensington, and Doc and Linda Mueller report that they have “wild” monarch caterpillars on their milkweed with abundant eggs and that they just received  this year’s shipment of mail-order monarch caterpillars (orders were delayed because of unexpectedly large demands for monarch caterpillars!).

I hope that our final migration and overwintering count improves over last year! So many people around the country are trying to pitch in to save the monarch! Plant some milkweed! Plant native plants (for nectar fueling sites!)! Use fewer pesticides! All of Nature will benefit from these steps, and we will help bring the monarchs back!





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Signs of Summer 7: Amphibians

Wood frog in mating pond. Photo by D. Sillman

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Amphibians are the oldest group of terrestrial vertebrates. They arose during the Devonian Period of the Paleozoic Era some 370 million years ago and are the evolutionary forerunners of all of the terrestrial vertebrate groups. Most amphibians lay their eggs in water and have early life stages (larvae) that developed as aquatic organisms (tadpoles of frogs are an excellent example of this).  A few amphibian species, though, bypass both the need to lay eggs in water and the aquatic larval stages. In these predominantly tropical rain forest species, small, full-formed “adult versions” of the amphibian hatch from the eggs and immediately enter the terrestrial ecosystem.

Amphibians have been declining all around the world. Hays (Journal of Experimental Biology 213.6 (2010): 921-933) estimates that 70% of all amphibian species are decreasing in numbers and that 32% of all amphibians are facing immanent extinction. Reasons for the observed vulnerability of amphibians are complex: they are exposed to high levels of UV radiation in sunlight especially in their egg and larval pools, surface water sources have declined precipitously in quality especially due to the influx of agricultural chemicals from surrounding fields and the impacts of wastes from large numbers of domestic grazing animals. Also, the increased density and species diversity in the biotic communities of the water pools themselves (due to a reduction in the total number of suitable pools for habitation) has led to a rapid dissemination of diseases both intra-specifically and inter-specifically. The epidemic spread of the chytrid fungus is an example of this accelerated transmission of disease.

Amphibian skin is also extremely permeable. It allows oxygen and water and many other chemicals in the environment to freely pass into the body of an amphibian. Many amphibians, in fact, rely on this skin permeability to gather oxygen from their aquatic environments, but the uncontrolled accumulation of environmental pollutants can, of course, have very deleterious consequences.

Spring peeper. Photo by Well Tea, Wikimedia Commons

I have written a number of blogs about amphibians: I have talked about the wood frogs down at Ohiopyle ( see Signs of Spring 4, March 22, 2018), the amphibians in my yard ( Signs of Fall 5, October 6, 2016), and the hunt for salamanders at Harrison Hills Park (Signs of Summer 4, June 18, 2015).

Much of the published data on amphibians is quite distressing. Population declines, lack of reproduction, and actual extinctions of populations are the most common topics in scientific papers about amphibians. There are a few hopeful observations, though.

Chinese giant salamander. Photo by J. Joel, Flickr

For example, a paper published in Current Biology (May 21, 2018) explored the genetics of the six-foot long Chinese giant salamander and found that this largest, living amphibian in the world represents five (or maybe even more!) distinct species. These large salamanders inhabit freshwater habitats in China and tend to move only slightly from their place of birth.  The consequence of this is that each distinct species is highly adapted to the specific conditions of their ancestral habitats. Recent conservation programs in China, though, which have not been very successful, have assumed that these giant salamanders represented only a single species! So, captive breeding programs and subsequent re-introduction of the young salamanders that they produce have generated many cross-species hybrids and have not paid attention to matching the specific species to their specific types of habitats. Hopefully, the knowledge of the existence of the multiple species will allow a more precise breeding system to be established and lead to a re-introduction program that more closely matches each species with their optimal habitat conditions thus giving these extremely endangered species a better chance at recovery.

In Panama in the first decade of the Twenty-first Century, the invasive chytrid fungus decimated native frog populations. Researchers recently returning to Panama studied both the chytrid fungus (and its pathogenicity) and the immune systems of the native frog species (in particular the protein systems secreted by glands in the frog’s skin which have protective, anti-fungal properties). They found that the chytrid fungus(which was thought to have been introduced to Panama by human transport) was unchanged in its ability to infect amphibians. This surprised researchers who thought that the virulence of the fungus would have declined as it established an equilibrium with the native frogs. Many native frog species, though, have developed skin secretory proteins that are increasingly effective at killing the chytrid fungus. This change in skin proteins suggests an on-going, relatively rapid evolutionary change in the frogs in response to this extremely destructive pathogen. This study was published in Science (359: 1517-19, March 29, 2018).

Hellbender salamander. Photo by B.Gratwicke. Wikimedia Commons.

And, finally, very close to home: a fisherman fishing in the nearby Kiskiminetas  River this spring hooked (and then videotaped and released) a hellbender salamander. The hellbender is the third largest salamander in the world (total length is up to 29 inches) and its eastern North American distribution has been rapidly shrinking due to habitat degradation. Hellbenders require clean water with high levels of oxygen (usually generated by fast turbulent waterflow over large, irregular rocks). They primarily eat crayfish but will also take small fish (especially in the winter).

The discovery of a hellbender in the Kiski River is an incredibly powerful affirmation on the on-going ecological recovery of this once polluted and acidified stream. Insects returned to the Kiski over recent decades followed by an array of fish species. And now, we have hellbenders! Can mussels and otters be far behind? (see Mary Ann Thomas’ article in on-line Valley News Dispatch (May 3, 2018).

Amphibian populations reflect the quality of surface water resources. As surface waters are polluted and degraded, the amphibians decline, and as surface waters are rehabilitated and protected, amphibians rebound. We need to recognize that water is our most precious and our most important resource. Our own survival depends on on water! We need to protect all surface water systems. Keep your eyes on the amphibians to see how we are doing!






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Signs of Summer 6: Cavity Nesting Team, Year #4!

Photo by D. Sillman

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Over the past four years I have written a number of articles about our Cavity Nesting Team study up at Harrison Hills Park in northern Allegheny County. This year we have twenty-nine nesting boxes scattered across the park and the Team started our 2018 monitoring on March 31. We have built up a steady accumulation of observations and hypotheses during the years of our study. Our findings from 2015 helped us better understand the optimal location variables for our nesting boxes (and our relocated 2016 boxes were almost all utilized for nests!). Our 2016 data helped us design two experiments for 2017 in which we tried to regulate house wren nesting in our boxes (house wrens are very destructive to nesting blue birds and tree swallows). The results of our experiments in 2017 were not very successful but we re-tuned some of our 2017 ideas for the 2018 season and may have finally achieved a sustainable equilibrium between blue birds, tree swallows and house wrens.

This year’s Cavity Nesting Team consists of ten volunteers: Deborah and I and Sharon Svitek take turns monitoring the boxes in and around the “High Meadow.” Patrick and Mardelle Kopnicky and Dave and Kathy Brooke check the boxes around the “Bat House Meadow.” Chris Urik and Kristi Cihil take turns monitoring the boxes at the park entrance and up in the fields near the Environmental Learning Center, and Paul Dudek checks the boxes around the pond and soccer fields in the southern end of the park. We also had a great group of student volunteers from the Harvest Baptist Church who helped us out during our May monitoring.  Data from our observations are uploaded to an on-line Google spreadsheet, and each week Deborah compiles and distributes the growing data tables to each member of the team. Also, each year Chris Urik has made new GPS maps of the park showing the precise location of each nesting box.

Photo by D. Brooke

As I have talked about before, native cavity nesting bird species (eastern bluebirds, tree swallows, house wrens, Carolina wrens, titmice, chickadees, nuthatches, etc.) naturally use tree holes for their nesting sites. These holes are most often found in older, often dead or dying trees, and they are typically abandoned cavities that have been chiseled out by woodpeckers. The lack of the these older trees in most forests has led to a “housing crisis for these cavity nesting species. Nest boxes, of course, are artificial substitutes for these natural tree holes.

So what have we seen so far in 2018?

Blue bird eggs. Photo by C. Urik

We saw our first blue bird nest on April 19 in a nesting box near the park’s Environmental Learning Center, and the first eggs were seen a week and a half later (April 28). Two weeks later (May 14) these eggs had hatched into nestlings and by then a large number of other boxes throughout the park were being utilized by nesting blue birds. In the first six weeks of our study eleven boxes had blue bird nests and thirty-three eggs were counted. Also during this initial period of the season, two boxes had tree swallow nests started (no eggs yet) and four boxes had house wren nests (also no eggs yet).

In the next three weeks two more boxes (13 total) had blue bird nests (43 eggs total with 28 nestlings and 24 fledges), one more tree swallow nest was built (3 total boxes with 15 eggs and 7 nestlings), and four more boxes had house wren nests (6 total boxes with one observed egg). A number of these house wren nests were “dummy” nests built by male house wrens as part of their mating displays. We diligently removed these practice nests in an attempt to distract the wrens from actual nesting. We also observed in this time frame one chickadee nest (0 eggs).

In the next four weeks blue bids added four more nests in boxes (17 total (3 more than in 2017!)). There were 63 blue bird eggs counted and 33 nestlings and 25 fledges observed. The “spring/early summer” nesting period of the blue birds occurred right on schedule! Some new blue bird nests were observed on July 1 indicating the start of the blue birds’ second, “late summer” reproductive phase.

Tree swallow nestlings. Photo by D. Brooke

Four nesting boxes had tree swallow nests and 20 eggs were observed. These eggs were primarily laid during the “summer” time period after the initial blue bird reproductive cycle but before their later “late summer” second reproductive event. This tree swallow egg total was very comparable to our 2015 observations and was a significant rebound from the very low tree swallow eggs production of 2016 and 2017. We had speculated that the dry summers of 2016 and 2017 had inhibited the emergence of the aquatic insects upon which the swallows rely to feed their nestlings. The very wet summer of 2018 must have generated a very rich population of these important food items. Further, all twenty tree swallow eggs resulted in viable nestlings, and all twenty nestlings successfully fledged.

Nine nesting boxes had house wren nests and 13 eggs were observed. One of the wren nests was the chickadee nest noted in the previous time period. The wrens usurped the nest from the chickadees and laid their eggs in the formed nest (it is not known if the chickadees had laid eggs or if chickadee nestlings had hatched in the nest, but if they had, they were destroyed by the wrens). No fledges from any of the house wren nests, though, have yet been observed. In past years, the house wrens nested and reproduced concurrent with the early blue bird nesting cycle (“late spring/early summer”).This year’s wren reproduction, though, is later in the season (corresponding more to the middle summer reproduction cycle of the tree swallows). Possibly this delay was due to both the Team’s interference with the wrens’ “dummy” display nests and also our moving a number of nesting boxes away from the park maintenance area (an hypothesized habitat refuge for the wrens). So far, the house wren reproduction efforts have not been successful. No fledges have been observed from the 13 eggs!

House sparrow nestlings. Photo by P. Kopnicky

For the first time in our study we have observed house sparrows (“English sparrows”) in one of our nesting boxes. These alien, invasive birds are very destructive (they invade established blue bird and tree swallow nests and destroy eggs and kill both nestlings and adults). The location of the park far from human habitations has insulated us from these birds, but here in the fourth year of our study they have finally shown up. Four eggs developed into four fledglings in one of the boxes near the Environmental Learning Center. It is possible that this house sparrow nest was built on a blue bird nest and possibly even on top of the dead bodies of some blue bird nestlings or adults. Since house sparrows are not native species, we were well in our legal rights to dispose of their eggs and even their nestlings, but none of us had the heart to do so. We hope that the fledged house sparrows will fly off to a habitat more suited to their needs (there is a McDonald’s and a Burger King not all that far away in Natrona Heights). We will, though, keep an eye out for them here in the park!

We still have two months left in our nesting box season. Our monitoring will run through Labor Day!  It is likely, barring some calamity, that we will exceed last year’s record numbers of blue bird nests/eggs/fledges. We have also had a very satisfying reproductive year for our tree swallows! If we can keep the house wrens under control and prevent an invasion of house sparrows, the cavity nesting bird community of Harrison Hills Park looks to be robust and healthy!



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Signs of Summer 5: Insects (good, bad and “other”)

Aedes aegypti Photo by J. Gathany CDC Wikimedia Commons

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The relationship between insects and humans is complicated. Many people initially react to the word “insect” with the image of household vermin, or a biting/stinging nuisance, or a disease transmitting vector, or a crop/garden destroying pest. This initial reaction might then give way to the recognition of all of the “good” that insects do (pollination, decomposition and functioning as a broad base for many important food chains). As I wrote a few years ago (Signs of Spring 13, May 19, 2016), even mosquitoes do some “good” in their ecosystems.

Krefeld, Germany, Pixabay

A one hundred year old, volunteer organization called the Entomological Society Krefeld has been keeping a close eye on the insects of west-central Germany. They just reported (in the October 18, 2017 edition of PLOS ONE) that over the past 27 years populations of flying insects in sixty-three nature preserves surrounding the city of Krefeld have declined 76%. These nature preserves are relatively small, well maintained “island” habitats (primarily grassland or heathland) that are located in between the extensive agricultural fields and cities and towns of west-central Germany. The purpose of these areas is to create habitats conducive to the maintenance of biodiversity. The observed precipitous drop in flying insects in these biodiversity refuges, then, is particularly disturbing.

The authors of Krefeld paper speculate that pesticide use in the surrounding agroecosystems, or the destruction and disruption of surrounding habitats by human activity or the environmental degradation from pollution may be causing the observed declines in the flying insects. Further studies are being proposed to look at the impacts of these declines on pollination, food chains (especially in insect-feeding birds) and nutrient cycling.

Black-legged tick. Photo by D. Sillman

There are some insects and arachnids, though, that are thriving in our human-modified world. The Center for Disease Control (CDC) released a report on May 1, 2018 that describes a 300% increase in human diseases transmitted by mosquitoes, fleas and ticks in the United States over the past ten years. The report concludes that warmer weather is the most likely cause of this rapidly increasing number of vector-transmitted, human illnesses. Increases in mosquito transmission of the Zika virus and tick transmission of the bacterium that causes Lyme disease were major components in the overall rise in these statistics.

Gypsy moth infestations, though, are notably less severe than they were even five or ten years ago. In large part the decline in this alien invasive insect is due to the effectiveness of an introduced fungal pathogen that kills the gypsy moth caterpillars. The fungus (Entomophaga maimaiga) has been used since the early decades of the Twentieth Century as a biocontrol agent against the gypsy moth. Gypsy moths were accidentally released into North American forests in 1869 and have been spreading and wreaking havoc ever since (see Signs of Spring 13, May 21, 2015 for a review). The fungus  has been used for the past eighteen years in coordination with a multi-state, integrated pest control program coordinated by the Federal government called “Slow the Spread of the Gypsy Moth” (STS), and researchers at Cornell University have developed ways to monitor the dispersal of the fungal spores from infected populations. They determined, in a 2017 paper in Applied and Environmental Microbiology, that a spore cloud can travel up to forty miles from its site of release. Further, only one spore is needed to fatally infect a gypsy moth caterpillar!

Oak processionary moth. Photo by B. Sale, Wikimedia Commons

Another insect that is thriving in the human-modified world is the oak processionary moth. This moth is a native of southern Europe, but it has slipped off of the European Continent where it is well controlled by a variety of predaceous beetles, parasitic flies and wasps and fungal pathogens, and entered the predator and parasite free ecosystems of southern England. The transplanting of oak seedlings infected with oak processionary moth eggs from Europe to England in 2005 is the likely event that led to this invasion.

The caterpillars of the oak processionary moth makes extensive, white webbing on infected trees and are capable of stripping entire trees of their leaves. The denuded oaks are then extremely susceptible to further damage from drought and a wide variety of pests and pathogens. As we have learned here in North American in our long battle with the gypsy moth (another invasive that favors oak trees) a given oak tree can withstand a year or two of defoliation but then with its metabolic reserves exhausted will be unable to make new leaves and will die.

To add to all of these potential ecological problems associated with the oak processionary moth, there is also a serious human health hazard to consider: the hairs of the caterpillars contain the toxic protein thaumetopoein. Thaumetopoein acts as a protective chemical for the caterpillars to help them avoid predation. The tiny hairs containing the chemical, though, can be released into the caterpillars’ environment where they can persist for up to five years. Thaumetopoein is capable of causing serious allergic reactions ranging from contact dermatitis to anaphylactic shock in sensitized humans.

Great efforts are being made to contain the oak processionary moth in the southern regions of England. Research is also ongoing to try to find an effective biocontrol regime against it. We have just begun, after 150 years, to deal with the gypsy moth invasion. We don’t need another invasive insect attacking our oak forests.








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Signs of Summer 4: More on Bees

Imidacloprid (a neonicotinoid). Drawing by Monolemma, Wikimedia Commons

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Neonicotinoids are a group of insecticides that are molecularly similar to nicotine. Nicotine itself is produced by a wide variety of plants including tobacco (in very high levels) and tomatoes and potatoes (in very low levels). In these plants the ecological purpose of the nicotine is to act as a protection against insect herbivory. Nicotine is, then, a “natural” insecticide. Synthetic neonicotinoids were produced commercially starting in 1985 and were approved for use in United States in 2003. These chemicals were rapidly incorporated into our agroecosystems and by 2013 were being used to control insects on almost all corn grown in the United States and also most of the cotton, sugar beets, and sorghum. Soybeans, rice, fruits and vegetables have also extensively been treated with neonicotinoids.

Neonicotinoids and their breakdown products, compared to carbamate and organophosphate pesticides, are less toxic to vertebrates (mammals and birds) but have been correlated with serious, non-target impacts on a variety of insects including pollinators like honeybees and bumblebees. These impacts of neonicotinoids led to a discussion among EU countries about the safety of these pesticides (see Signs of Summer 11, July 27, 2017). Finally, on April 27, 2018 the EU voted to ban the use of three of these neonicotinoid pesticides in any open agricultural field. They cited overwhelming evidence that linked these three pesticides to declines in pollinators, butterflies, aquatic insects and insect eating birds. Similar restrictions and bans have been proposed in the U.S. Congress, but no action has yet taken place.

Honeybees, Public Domain, Pixabay

A study recently published in Current Biology (March 22, 2018) examined how honeybees and bumblebees metabolize two of the neonicotinoid pesticides. One of the chemicals in the study was imidacloprid which is a particular toxic neonicotinoid and one of the three that was banned for use in open fields in the EU zone. The other was thiacloprid which is a much less toxic neonicotinoid and one that is has not been banned for use in agricultural fields in the EU zone.  Researchers found that in honeybees a cytochrome P450 protein system rapidly broke down the thiacloprid into substantially less toxic compounds. These bees, then, were able to survive in environments in which the thiacloprid was used to control pest insects. Bumblebees used a different protein system to break down the thiacloprid but achieved similar tolerances to it. The imidacloprid, on the other hand, was not metabolized into less toxic products by either honeybees or bumblebees. Both honeybees and bumblebees, then, were significantly harmed in environments in which imidacloprid was used.

Field studies in which multiple pesticides and fungicides are combined (a condition that more closely replicates actual chemical conditions of treated agricultural ecosystems) are being conducted. It is significant, though, to recognize that not all neonicotinoids affect bees in the same way. The banning of the most lethal of these chemicals should be a goal for all concerned individuals and institutions.

Honeybee waggle dance. Photo by Tautz and Kleinhenz, Wikimedia Commons

The “waggle dance” is one of the best known and one of the most carefully studied systems of communication among individuals of an invertebrate species. Honeybees are able to communicate to their hive mates via a series of dancing body movements the locations and distances of pollen and water sources and initiate a mass flight of the hive’s workers to gather up these important resources. A study at the University of Tokyo (published in Entomological Science on November 5, 2017)  describes a new version of the waggle dance that communicates both a danger to the hive (in the form of attacking wasps) and a call to protect the hive (via the gathering of odorous plant materials (like the leaves of Nepalese smartweed) which is then spread across the entrances to the hive in order to repel the wasps). This new waggle dance is referred to as the “war dance” of the honeybee!

And, finally, bees have been added to the very select group of animals (that include humans, non-human primates and the African grey parrot) that can comprehend the concept of “zero.” In an incredibly elegant experiment neuroscientists at the University of Melbourne in Australia and in the Universite de Toulouse in France trained bees to choose pieces of paper that had the fewest number of black dots in order to get a reward of sugar water. Once the bees were trained to choose the paper with the smaller number of dots, they were then given the choice between a piece of paper with one dot and a piece of paper with no dots. These bees chose the blank sheet pf paper 63% of the time thus demonstrating that they recognized that zero dots were less than one dot.

Possibly bees have evolved the ability to notice the absence of something in order to more efficiently forage or avoid predation. Perhaps there are other explanations for these amazing observations. As the old joke goes: to whomever invented the zero ….. thanks for nothing!

Photo by D. Sillman

And a quick update on my mason bees! I have over one hundred sealed nesting tubes in my “bee basket” and cylinders. The bees were incredibly active for just over five weeks. Along with the forsythia (which had just started to flower when the bees first emerged) daffodils and hyacinths and early clover all flowered during the bees’ active period and provided them, I am sure, with abundant pollen and nectar. Now I wait until next spring! Mason bees are fun pets!


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Signs of Summer 3: Vagility and Salmon Hatcheries

Arctic tern. Photo by K. Pikner, Wikimedia Commons

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“Vagility” is a word that I first came across in a February 19, 2018 article in the Science section of the New York Times. Its word root, “vagile,” means “free to move about,” and its application in ecology refers to the degree by which an organism is able to move around in its environment. In other words, the freedom an organism has to migrate.

There are many examples of and also many types of migration. Some animals migrate over very long distances (like arctic terns that breed in the tundra around the Arctic Ocean and then spend their “winters” in the “summer” over the oceans around Antarctica. It is said that no other animal species sees as much sunlight in its life as the arctic tern!). Other animals fly or walk just a thousand miles or two as they move along their yearly migration routes (many of our summer birds (like the scarlet tanager, Baltimore oriole, rose-breasted grosbeak) spend their winters in South America and return here to the north to breed in the summer). The herds of wildebeest, zebra and antelope in East Africa circle the Serengeti and  Masai Mora ecosystems completing an 1800 mile annual path in their search for fresh grass and safe places to give birth to their young. Wapiti and pronghorns migrate up and down the slopes of the Rockies making use of the abundant grasses and protective landscapes of the mountain slopes in the summer to breed and then more sheltered lowlands to survive their brutal  winters. Eastern towhees (a bird Deborah and I have been watching recently in and around our house) spend their winters in nearby sheltered valleys and then spread out through the eastern forests to mate and rear their young in the summer.

Wildebeest. Photo by J. McCarthy, Pixabay

All of these species (and so many more!) rely on their freedom of movement (their vagility) in their environment to survive, feed and breed. These movement patterns may be hardwired into the species’ DNA or they may be facultative responses to conditions of their environments. Abundant winter food, for example, can reduce the migration urge in many species (we have talked about this in previous blogs for American robins and sharp-shinned hawks). Other species, though, migrate regardless of food abundance (ruby-throated hummingbirds, for example, will migrate south in the early fall even if abundant nectar feeding stations are available).

Photo by Ongayo, Wikimedia Commons

Human activities and constructions, though, can interfere with a species’ ability to migrate. Highways, fences, farm fields, oil and gas wells, urban and suburban buildings and streets can all get in the way of natural species movements. Even if they don’t stop migration completely, these human-made impediments can slow down or restrict an animal’s freedom of movement.

A large, global study on animal movements was just published in Science (26 January, 2018). In this study researchers fixed GPS collars on 803 individual animals of 57 different species that ranged in size from pocket mice to elephants. Their movements were precisely recorded and then analyzed taking into account the degree of human development in the specific animal’s environment. Overall, it was found that animals in human developed environments move between one third and one half the distances of animals living in environments not developed by human beings.

The proximate benefits of migration to each species are fairly obvious: the species finds a safe habitat in which to reproduce and new food resources to sustain it. It also spreads out its resource use so as not to overly degrade its environment. But there are also more distal benefits of migration that include seed and nutrient transport  sometimes over vast distances. The long term consequences of restricting an animal’s vagility, then, may not only be increased mortality and decreased fecundity of individuals of that species, but also a spiraling decline in the viability of their entire ecosystem.

As Dr. Matthew Kauffman (a wildlife biology professor at the University of Wyoming and one of the authors of this Science article) put it: “Wild animals on an intact landscape move in sync with their needs. When you develop the landscape, that leads to less movement and they are less in tune with the naturally occurring pulse of the landscape.”

Image by T. Knepp, USFWs

Pacific salmon species exhibit remarkable vagility. They hatch from eggs that have been fertilized in freshwater streams and lakes that, depending on the salmon species, may be located hundreds of miles inland and often high up in the mountains of the coastal ranges. Then they are eventually swept downstream into the Pacific Ocean. These salmon may live 3 to 6 years and spend anywhere from 3 months to 3 years in freshwater before they make the transition to marine existence. Adult Pacific salmon at the end of their lives make the often incredibly laborious return to their birth streams or lakes to spawn and then die. Since only a very small percentage of adult salmon that attempt this return migration are successful, this vagile event represents a powerful, evolutionary filter that selects for only the most vigorous and evolutionarily “fit” individuals.

These two phases of salmon migration are not only integrally important to the survival of the salmon themselves, but they also contribute to the overall vitality of these Northwestern ecosystems especially through the delivery of high quality and abundant food to the myriad of salmon predators that inhabit the terrestrial and aerial habitats along the streams.

Wild-bred salmon, though, are declining in the Pacific Northwest primarily due to human mediated impacts. Hydroelectric dams block many of the rivers, spawning habitats are becoming significantly degraded, and water quality all along the streams and even out in the ocean has been compromised by excessive pollution. Further, wild populations of salmon have also been harvested historically in very unsustainable ways.

Photo by R. Hartnup, Flickr

To compensate for these precipitous declines in wild salmon, salmon hatcheries have been established throughout the Northwest to breed, feed and release smolts into the region’s streams. Not surprisingly, though, these hatchery-raised salmon are different from the wild-bred varieties.

Although the hatchery-bred salmon look like and act like their wild counterparts, their survival rates in both freshwater streams and in the open ocean are much lower. Further, if a hatchery-raised salmon does survive long enough to spawn, it produces fewer offspring than the wild-raised fish.

Researchers at Quebec’s Laval University wanted to know if hatchery life was affecting gene selection and expression in the salmon. A 2012 study suggested that hatchery conditions (confined spaces, crowded conditions, high levels of fish waste in the water) might be selecting for specific genes that were counter-adaptive to open stream and ocean existence. The constant influx, though, of wild genes into the hatchery stock made a gene-level explanation unlikely. So the Laval research team looked not at the genes of the salmon but, instead, at their epigenetics.

Methylation of genes occurs during embryonic development and continues after birth. When a gene is methylated its activity is reduced. Depending on the magnitude of the methylation this reduction in activity may be a complete shutting down of the gene. The Laval team found that hatchery-raised salmon had 100 genes that were methylated compared to wild salmon stock, and that ninety percent of these genes were hypermethylated. Some of the hypermethylated regions contained genes that affected the salmon’s immune system and neuromuscular control. Also, regions regulating feeding behaviors and appetite were significantly impacted. Possibly, these epigenetic alterations were making the hatchery-raised salmon less able to survive and thrive in the wild ecosystems into which they were introduced.

Results of this Laval University study were published in the Proceedings of the National Academy of Sciences of the United States of America (5 December, 2017).

So animals need to have the freedom to move about in their environments. When these movements are restricted, both the animal species and its environment are stressed. We need to be careful with our solutions to these migrations problems, though. Often even simple, logical solutions have novel and unexpected consequences.




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Signs of Summer 2: Our Yard Ecosystems (part 2)

Photo by D. Silman

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Last week we talked about the plant components of our home-ecosystems. Listed in that post were estimates of $30 billion dollars spent each year by Americans on lawns and $14 billion dollars spent on flowers. These figures need to be augmented by a guess at how much is then spent on home-ecosystem trees (purchasing, planting, trimming, removing etc.). I tried to find this data but, unfortunately, only could reliably find how much we Americans spend on Christmas trees each year ($1.32 billion)). So, just to keep the narrative going, I am going to estimate $20 billion for the tree component for our home-ecosystems. I think that it is a good guess and is probably an underestimate.

So, putting all these figures together, we Americans spend about $64 billion dollars each year creating and maintaining the plant components of our home-ecosystems! To put this figure in perspective, $64 billion is greater than the GDP of 138 countries on Earth according to a publication by the United Nations Statistic Division (2016). It is, then, a lot of money.

Photo by D. Sillman

Once you have built this exotic, invasive species laden, botanical paradise, though, it fills up with animals at relatively little cost! As they (sort of) said in the movie “Field of Dreams,” “if you build it, they will come!” You can, if you choose, and 65 million Americans do choose to do this, put out a variety of seeds and feeding stations to attract birds and a constellation of other wildlife, but even if you don’t do that, a considerable number of animal species will migrate into and establish themselves in your home-ecosystem. Americans, by the way, spend $3 billion a year on bird seed! That’s a pretty large amount of money, but a pretty small percentage of the overall home-ecosystem cost.  I talked about the motivation for providing food for wildlife and its possible consequences in a previous blog (Signs of Winter 11, Feb 11, 2016).

So what kinds of animals inhabit our home-ecosystems?

Here in Western Pennsylvania all sorts of furry, feathered, and scaly guys show up when any type of cover or edible vegetation is established. Plant-nibbling critters (like white-tailed deer, woodchucks, cottontail rabbits, meadow voles, etc.), an array of seed and fruit eaters (like gray squirrels, red squirrels, fox squirrels, white-footed mice and chipmunks) and some predators and omnivores (including voles, skunks, racoons, opossums, toads, garter snakes, black snakes and maybe even red foxes and coyotes) are all likely to become part of the home-ecosystem.  If you add your own domesticated animals (dogs and cats) to the mix, you have a pretty diverse animal community, and if you are lucky, you might even have a black bear come and visit your house! Bats may also use parts of the home-ecosystem for their roosts, although, sadly, their numbers are dwindling in our area.

Photo by D. Sillman

White-tailed deer are actually becoming more abundant around human habitations than they are out in more rural habitats. Fewer predators and little or no hunting pressure have contributed to this “city-deer” transformation. There is also some speculation in the scientific literature that the exotic plants of a suburban landscape may be more calorie rich and nutritionally fitting for deer than their usual fare out in the surrounding countryside (see Signs of Spring 1, March 1, 2018).

Many of these animals will do considerable damage to the plant community of your home-ecosystem. Wildlife damages incurred by metropolitan residents in the U.S. have been estimated at $3.8 billion annually (PA Game Commission, 2014). The Game Commission estimates that about 10% of this damage is caused by white-tailed deer.

Photo by D. Sillman

Looking over my notebooks, I count 18 species of mammals as regular or occasional components of my home-ecosystem, along with 8 species of reptiles and amphibians and 55 species of birds. I put out bird seed (black oil sunflower seed, peanuts and shelled corn) every day, and I maintain a year round source of water (heated bird bath in the winter). I also plant a garden each year and much of that production, unfortunately, goes to sustain some of the plant-feeding wildlife species.

As I pointed out in Signs of Spring 8 (April 6, 2017) humans underwent significant evolutionary changes as a result of the foods and processes of agriculture and as a consequence of living in the crowded, stressful conditions of cities. The overall diversity of the human genome decreased. Genes to digest complex carbohydrates and milk sugars were selected for and any flaws in immune system function were brutally selected against by the array of epidemic diseases that arose from contact with agricultural livestock. The ability to tolerate contaminated drinking water or efficiently metabolize the alcohols that were developed to replace simple water supplies for hydration were also positively selected for.

It is not surprising, then, that the animals that are coming into our home-ecosystems are also undergoing evolution! Isolated white-footed mice populations in the parks of New York City are showing genetic changes that enable them to live in habitats enriched with formerly toxic levels of heavy metals like lead and cadmium. Cliff swallows living near busy highways are developing shorter wings that enable them to more easily evade collisions with passing cars. The beaks of house finches and great tits are becoming larger and more robust so that they can more easily eat the often hard-to-crack seeds found in bird feeders. In cities a new species of mosquito has evolved that is able to breed in the waters of underground sewers and subways instead of the above-ground puddles preferred by its progenitors. Crested anole lizards in Puerto Rico are developing longer legs and stickier toes to enable them to better climb the side of buildings. (See M. Johnson and J. Mushi-South, Science,  03 Nov 2017).

So, the fauna of our home-ecosystems are quite diverse and rich. One friend has told me that he has spotted 21 different mammals in his less than one acre, suburban yard, and reports that he still hasn’t seen a red fox, a flying squirrel or a coyote! Some other friends have had a mink drop in to their garden pond and eat their fish and a black bear guzzle down the sugar water in their hummingbird feeders!

Keep your eyes open!!

Happy Summer, everyone!





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Signs of Summer 1: Our Yard Ecosystems (part 1)

Photo by M.O.Stevens, Wikimedia Commons

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Each of us who owns a house manages the ecosystem that surrounds it. We make choices about what plants we want to grow in our home-ecosystems, and we make choices about how controlled we want those ecosystems to be.

The most prominent feature of a yard-ecosystem is usually the lawn. On average, 75 to 80% of a house lot area is set aside for grass. Most lawns are closely trimmed and densely vegetated with tightly packed grass plants. Fescue and bluegrass are the dominant grasses. Most lawns are extremely controlled monocultures: no clover, no dandelions, no ground ivy, and no “weeds” of any kind. A monoculture, be it lawn or cornfield, is an unstable ecosystem. Successional forces and waves of opportunistic, invading plant species (the “weeds”) exert immense pressures on the system. These forces would very quickly change a lawn- grass system into a system dominated by annual weeds. A great deal of energy has to be

Photo by D. Sillman

employed to keep these successional forces at bay.

The grass manager (i.e. the home owner) has to set up a regime in which the grass plants are vigorously stimulated to grow (by the addition of water, fertilizer, lime etc.), and in which less desirable plants (the “weeds”) are selected against by the frequent plant tissue destruction caused by mowing (and the more you “feed” and water a lawn the more you have to mow it!), by the very occasional direct removal of “weeds,” and by the very frequent, broad application of herbicides designed to kill non-grass plants. These steps are the only ways to insure that a lawn remains a singular grass ecosystem.

The cost of this control is astounding. Here are some numbers for lawns in the United States (derived primarily from EPA, Audubon Society, and The Garden Club of America publications and web sites):

  1. 54 million people mow their lawns each summer weekend, 800 million gallons of gasoline are used in gas lawn mowers each year,
  2. 17 million of these gallons of gasoline are spilled during refueling mishaps,
  3. mower exhaust and the volatile organic chemicals from the gas spills contribute to lower atmospheric ozone production (“smog”) all summer and also generate about 5 % of the nation’s total air pollution,
  4. 78 million pounds of herbicides/pesticides/fungicides are used on lawns each year (with almost no oversight or control),
  5. 3 million tons of fertilizers are applied to lawns each year (again, with almost no oversight or control),
  6. 50 to 70% of the total residential water volume is used for landscaping (mostly to water lawns),
  7. a total of $30 billion is spent annually on lawns (installation, care, and maintenance).
  8. lawns in the United States cover approximately 50,000 square miles. This area represents the largest single, irrigated “crop” grown in the United States.

The growing economic and environmental cost of maintaining lawns, especially in regions of low rainfall, have begun to raise serious questions about the sustainability of this phenomenon. Added to these concerns are the realizations that the grass plants themselves that have assumed such a dominating presence in our urban, suburban, and rural landscapes are, in fact, non-native, and, frequently, invasive plant species. Even “Kentucky” bluegrass is a plant native to Europe, Asia, and northern Africa! These plants are invading and upending our natural floral ecosystems!

Norway maple, J. Billinger, Wikimedia Commons

The most common trees in the yards of my neighborhood are Norway maples, blue spruces, Norway spruces, and silver and sugar maples. The spruces are often of substantial sizes (more than a foot in diameter and 40 to 50 feet tall) with broad growth forms with little branch shading or limb pruning. Only in a very few cases are any of the trees in branch contact with each other. For the most part, the trees are widely separated and quite isolated. There are also some yellow and European white birch, yellow poplar, cherry, and crab apple trees growing in these home-ecosystems along with a variety of shrubs including rhododendron, azalea, burning bush, yew, privet, Rose of Sharon, forsythia, lilac, and a variety of forms of arbor vitae.

Now without getting too preachy or picky about the subject, it is important to consider the idea of “native” vs. “non-native” plants with regard to these tree and shrub species. The three most abundant trees are introduced, exotic species. The Norway maple is native to eastern and central Europe and has been, primarily because of its tolerance of a wide range of site conditions, extensively planted throughout the eastern United States.  The Norway maple, though, because of its prodigious production of seed and its tendency to form dense thicket masses in untended ecosystems, is classified by the National Park Service as an alien, invasive plant that should be avoided. The escape of this species into the wild has done a great deal of damage to native plants throughout the eastern United States.

Norway spruce, Photo by D. Sillman

The Norway spruce (which is native to northern Europe) and the blue spruce (which is native to western North America) have also both been widely planted as ornamental trees throughout the United States. Their respective reproductive and growth patterns do not generate invasive or destructive responses in unmanaged ecosystems, although both have “escaped” extensively from their landscape systems into surrounding forests and both have, undoubtedly, had some negative impacts on competing, native tree species.

Rhododendron, arbor vitae, and some (but not all) of the azalea types are native plants in our region. Burning bush (from northeast Asia), privet (there is a European form, a Japanese form, and a Chinese form), Rose of Sharon (from southeast Europe and southwest Asia), lilac (from Europe and Asia), forsythia (from eastern Asia), and yew (from England) are all exotic, introduced shrubs. Of these plants only the lilac and the English yew are classified as “non-invasive,” although both are recognized as having frequently “escaped” into surrounding ecosystems.  The other species (burning bush, privet, Rose of Sharon, and forsythia) have not only widely escaped but also have caused, according to the U. S. Forest Service, via their dense and destructive growth patterns, widespread declines in many native plant species.

Photo by K. Andrew, Flickr

Flower beds often border the home-ecosystem swath of lawn. Some typical home-ecosystem flowers include roses (a very old domesticated flower which probably originated in the Middle East thousands of years ago), crocuses, daffodils, and tulips (which are from southern Europe, North Africa, and Asia).  The “top ten flowers” planted in the United States (as listed by include lilies, sunflowers, tulips, roses, pansies, sweet peas, nigellas, marigolds, California poppies and Dianthus varieties (the “pinks,” sweet William and carnations). Of these only sunflowers and California poppies are native to the United States (there are some native lilies, but most garden varieties are from Asia). For potted plants the USDA indicates that chrysanthemums (Asia), orchids (mostly tropical species), geraniums (eastern Mediterranean), and poinsettias (Mexico) are the dominant plants sold in the United States. These flower represent (according to about 46% of the $31.3 billion generated each year by floral products industry!

So, from our grasses to our trees to our flowers, we have made and sustain (and pay steeply for!!) an ecological node of invasive plants all around our houses.

(next week: some animals of our home-ecosystems!)

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