Gray wolf. USFWS, Public Domain
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Over the past couple of weeks I have been talking about “re-wilding.” The basic idea of a re-wilding plan is to return a human-degraded ecosystem as close as possible to its pre-human impact, natural state. Re-wilding involves some substantial ecosystem engineering and re-modeling and, typically, the re-introduction of quite a few species.
Two weeks ago I talked about the program in Yellowstone National Park and the proposed program in Colorado of re-introducing gray wolves into ecosystems within which they were exterminated in the past century. These programs are excellent examples of limited, very focused re-wilding. For the re-introduced wolves to survive and reproduce in their new habitats, substantial work in habitat restoration and planning had to be done ahead of time to try to correct at least some of damage humans have done to these ecosystems.
Last week I talked about elk re-introduction to the human-made grassy plains of eastern Kentucky. This week I want to look at bison returning to Great Britain after 6000 year absence, California condors returning to soar over the giant sequoias in the Sierra Nevada Mountains, and lake sturgeon being returned to a polluted river in Ohio.
European bison. Photo by TalksPresenter09, Wikimedia Commons
In Great Britain populations of wild species have declined by 60% over the past fifty years making Britain one of the most wildlife depleted countries in the world. In an attempt to counter this disastrous trend, a plan has been formulated to re-introduce bison into a forested preserve in Kent in 2022. Britain last had bison (“steppe bison” (Bison priscus)) about sixty centuries ago. Steppe bison, sadly, have since gone extinct, but a close descendent, the European bison (Bison bonagus) will be taking on the role of ecosystem engineer in these modern forests in Kent.
Steppe bison once ranged all across Europe, the British Isles, Central Asia, Northeast Asia and North America. The species went extinct about 5000 years ago and was replaced in Europe by the European bison (also called the European wood bison) and in North America by a sequence of bison species that culminated in the American bison (Bison bison) (a species I discussed extensively a few weeks ago in Signs of Fall 5, October 22, 2020).
The European bison is slightly taller than the American bison and has noticeably longer legs. It also weighs a bit less than its American counterpart. The European bison is not able to run as fast as the American bison nor for as long a period of time, it is, though, quite agile and able to jump considerable distances and heights. The skull and cervical vertebrae of the European bison articulate with each other to form a neck angle that is slightly different than the one seen in the American bison. The American bison’s head has a more pronounced downward orientation which is very suitable for its almost constant grass grazing, feeding behavior. The European bison’s head on the other hand has a greater upward range of motion which allows it to browse up on branches and stems. Both the European and American bison, though, are large and very formidable creatures!
European bison are very selective feeders in their forested habitats. They kill certain tree species by browsing especially on bark and may also kill other species by vigorous rubbing and consequential abrading away of their protective bark. This act of killing trees opens up sun gaps in the often dense forests. These gaps can then support the growth of many other forest floor plants or even some sun-loving tree seedlings. The downed wood from the dead trees also provides protective habitat for small mammals and birds and an abundant food source for insects which are , in turn, preyed upon by a wide range of vertebrate and invertebrate species.
It is hoped that a number of bird species whose numbers have been steadily declining in Great Britain (including turtle doves and nightingales) may find these bison generated sun gaps with their complex physical structures and abundant food resources to be highly favorable habitats. The role of the European bison as an ecological remodeler has led to its designation as a keystone species in its forest habitats.
The European bison has been established in preserves all across Europe, but this proposed Kent herd would be the first in Britain. Their worldwide population currently is only 7500 individuals with half of these animals living in Poland and Belarus. Many of these bison herds are regularly given supplemental food (hay), but the British bison herd is proposed to be self-sufficient and entirely wild.
California condor. Public Domain
California condors (Gymnogyps californianus) with their nine and half foot wingspan are the largest land bird in North America. They are scavengers whose natural range once covered almost the entire North American continent. The arrival of humans in North America some 14,000 years ago reduced the large mammal populations of the continent and also disrupted the widespread distribution of their carcasses which, of course, were prime food sources for the condors. The condor’s range subsequently shrank down to the desert southwest and west coast and especially to the oak savannas and mountains of California.
California condors were put on the Endangered Species List in 1967 and designated as “critically endangered.” The condors became functionally extinct in the wild in the late 1980’s when all remaining birds were taken into captivity. At the time there were only 27 California condors left. Captive breeding programs were set up at the San Diego and Los Angeles zoos. Thus far these programs have generated a population of 518 condors.
Some of the captive bred birds have been released back into the wild at sites in northern and southcentral California and in Arizona. The released animals are slowly reproducing and their populations are both increasing in number and also expanding their distributions.
This past spring, California condors were spotted soaring over the mountains and giant trees in Sequoia National Park! Condors used to nest in cavities of the giant sequoias, and they are re-wilding themselves back into these magnificent forests!
Maumee River. Photo by J. Good, Wikimedia Commons
I have written about the Maumee River before (see Signs of Fall 13, November 30, 2017). It originates in northeast Indiana and the runs through northwest Ohio to the city of Toledo where it empties into Lake Erie. The Maumee is surrounded by agricultural fields from which it receives a great deal of runoff that is enriched with nitrogen and phosphates. Each summer the river warms up sufficiently to support a massive bloom of cyanobacteria (“blue-green algae”). These blooms extend downriver and out into the equally warm, shallow waters of western Lake Erie. These blooms have seriously compromised the water treatment plants in Toledo and put the health of many thousands of people in jeopardy.
Young lake sturgeon. USFWS. Public Domain
A little over a year ago (October 1999) the Maumee was the site of community-based re-wilding effort. With great public fanfare and financial support, three thousand, young lake sturgeon (Acipenser fulvescens) were released into the Maumee River. These sturgeons were each about seven inches long and some were equipped with sophisticated tracking devices so that their movements in Lake Erie and, possibly, the other Great Lakes or their tributaries, could be monitored.
Lake sturgeon are an ancient fish species. Modern individuals resemble fossils that have been dated back 136 million years. Lake sturgeon can grow to immense sizes with lengths up to eight feet! They also can live fantastically long, natural lives (males can live for 90 years, and females can live for 150 years!).
Lake sturgeon were once very abundant in the Great Lakes, but their current population is quite small. Overfishing, pollution, increased silt loads from accelerated soil erosion, and the degradation of spawning habitats on tributary streams have all combined to greatly reduce their numbers.
Lake Erie once had nineteen streams in which lake sturgeon spawned and reproduced, but now there are only two. Sponsors of the Maumee sturgeon release program were concerned that the Maumee River might be too degraded to support the returning sturgeon (sturgeon faithfully return to the stream where they are hatched), but extensive studies of the stream quality from Lake Erie back to the first large dam on the Maumee indicated that 7% of the river was in good enough shape to allow spawning and that 21% of the river was suitable to serve as nursery habitats for the young sturgeon. These numbers were deemed sufficient to support the Maumee sturgeons.
This re-wilding project in western Ohio has a very long time line. Male lake sturgeon return to their breeding streams only after 15 years of feeding and growing out in their large lakes, and female lake sturgeon return to their breeding streams only after 25 years!
My hope is that we all get to read about the “return of the sturgeon” to the Maumee in 2035 or 2045! I think that it’s a good goal for each of us!