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.
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.
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.
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!