By Bob DeGroot

Isolated islands around the world often have less species diversity than similar sized areas on the nearby mainlands. Although this phenomenon has been documented in a number of studies, the reasons for it was not entirely understood until fairly recently. In 1986, one of the world’s largest hydroelectric impoundments was flooded in Venezuela, and the resulting islands allowed scientists to study what happens to plants and animals when they are isolated.

Within seven years of the flooding, roughly 75-90% of the terrestrial vertebrates had vanished on the smaller islands. No large predators remained and the species that were left such as howler monkeys, leaf cutter ants, and iguanas had become overabundant. As a result of this overabundance of certain species, vegetation was being decimated. Fewer than five species of seedlings were growing where previously sixty to seventy species could be expected. The new seedlings were being eaten by leaf cutting ants as the tree canopies were being defoliated by howler monkeys and iguanas. In the absence of normal biological controls, it was inevitable that most of the plants and animals that survived the initial contraction of habitat, would themselves disappear in a few generations.

The same thing is happening all over North America as we continue to isolate our wildlife and plants on "islands" of protected land, fragmented and isolated by land filled with people. In many parts of North America, the demise of the top predators has resulted in release of small to mid-sized predators such as foxes, skunks, raccoons, opossums, and domestic house cats. This has resulted in widespread reduction in ground-nesting birds such as quail, pheasant, grouse, ducks, and certain warblers. The destruction of top carnivores has also allowed populations of herbivores such as deer or boars to explode in certain areas. Over browsing by these now abundant animals results in the loss of certain species of plants and trees and often prevents regeneration of these species. This is known as the "trophic cascade" effect.

Nature tends to stay in balance only as long as the animal kingdom remains intact. It falls out of balance when too many consumers of vegetative material or too many small predators exist. Humans seem to take notice of these occurrences only when some favored species begins to disappear. Many changes going on in nature are largely unrecognized and unseen by humans.

Reconnecting

Understanding what is going wrong in nature is the first step toward correcting it. Several environmental groups have recognized the island effect that exists within our current federal and state park systems, and have begun working toward designing large bioregions. Projects are underway to address the isolated habitat issue, and work is progressing toward providing permanent wildlife connecting corridors between parks and other ecologically sensitive areas. One of these ambitious projects will provide wildlife connecting corridors from the Yellowstone Park in Wyoming all the way through Canada and into Alaska. This is the historic range of large carnivores like the Grizzly Bear, Gray Wolf, and Cougar and needs to be protected for the survival of these large animals. Biologists have determined that Yellowstone Park, as large and beautiful as it is, is not large enough to sustain some large mammals. Other projects are similarly looking at connecting the southern tip of Florida to the mountains of the Carolinas, and connecting the Adirondack Wilderness Reserve System in New York to parks in Canada.

As we get closer to home, the Southern Appalachian Wildlands proposal is being developed to provide wildlife connecting corridors from Georgia up through the Carolinas and into Virginia and West Virginia. This Appalachian Mountain range extends into Maryland and Pennsylvania, and both states should be part of this ambitious plan. One of the goals in starting the Maryland Alliance for Greenway Improvement and Conservation (MAGIC) was to work on this project. People in Pennsylvania are also working now to include their state in this ambitious project to protect a highlands ecosystem in the East.

Habitat fragmentation is a problem that exists in Maryland among all its isolated parks and forests. Each forest and park is small and is fragmented by human habitation and roads from connection to other protected lands. To ensure the viability of all species, we need to examine the requirement to interconnect parks and forests with corridors to provide for gene dispersal of plants and animals. More importantly, we need to do this before the growth of human population makes it impossible.

As has been done on similar ecosystem projects, Maryland’s Department of Natural Resources (DNR) looked at the largest remaining roadless areas and currently protected land in Maryland to try to connect these areas with ecological corridors. DNR understands the need to connect fragmented land, and has created a program called the "Green Infrastructure". Its purpose is to determine what areas in Maryland have the greatest concentration of biological diversity, and decide how best to connect them with corridors to ensure permanently protected conduits for movement of plants and animals. MAGIC supports this ambitious DNR program and will work toward its eventual success. The third edition of Maryland’s Greenway Atlas is to be published by DNR in October 2000, and will show the most ecologically important lands in Maryland, along with the most likely connecting corridors. Each county will then have a blueprint for establishing protected areas for its most sensitive natural resources.

About 78% of Maryland’s forests are in private hands. This provides a more difficult problem for preserving wildlife habitat than it would if the state owned more forested land. Western states have a definite advantage when it comes to ecosystem protection because the Federal Government owns 50% or more of the land in several western states. Large areas of the West still remain roadless and unlogged, and have become prime habitat for wildlife and excellent locations for habitat protection proposals. Wildlands proposals for these areas looked initially at roadless areas of 100,000 acres or more for wilderness protection, while in Maryland we are down to looking at areas as small as 500 acres.

"Keystone" and "umbrella" species now living in Maryland need to be designated to determine how much habitat should be provided to sustain them. Keystone species are defined as a species that enrich ecosystem function in a unique or significant manner disproportional to their numerical numbers. Often a keystone species will be the largest mammal or carnivore, but beaver and prairie dogs have also been identified as keystone species.

"Umbrella" species generally need large areas for their daily or seasonal movements. Large mammalian carnivores are often designated as umbrella species because they are wide-ranging, but herbivores and raptors can also serve this purpose. Protecting habitat for the largest animals is often beneficial for several species since biologists have found it provides an umbrella of protection for many smaller species. One of the largest species living in Maryland today is the black bear, and protecting it and its habitat should be a priority endeavor.

Importance of Old Growth Forests

In the early 1900s, nearly all forests in Maryland had been cut down and the land was denuded. The resulting erosion filled many streams with sediment and killed many native fish. Deep water ports like Anacostia silted in and were then closed to deep draft vessels. Large animals like elk, bear, cougar, wolves, deer, beaver, and bobcats were nearly exterminated, and only a few species like bear, deer, and beaver ever recovered in any numbers. Although the fate of large animals and birds have been closely monitored and their demise recorded for history, the fate of smaller animals like salamanders, beetles, and bacteria is largely unknown. Many plant species like ferns, lichens, herbs and fungi were also largely overlooked.

In the last 100 years, many of these forests and streams have slowly recovered. New forests now appear on nearly 43% of the land surface in Maryland, but none of these forest are considered old growth forests by scientific standards. Even though the forests have never recovered to anything near their original stature, about 71% of the Maryland forests are now considered by the lumber industry as sufficiently aged to be worth cutting again. Out of all this forest, only about 12% belongs to the State, and most of the remainder is owned by the forest industry or private individuals.

Studies have shown forests must be 150 to 200 years old before the appearance of some species of lichens. Certain herbaceous plants require from 40 to 150 years to regenerate, and will never recover in a forest with a logging cycle of 100 years or less. Studies conducted on forests 90 years after major events, such as a clearcutting of trees, have found no evidence of the recovery of vernal herbs normally expected in the area. Many plants disperse at extremely slow rates, and once they are eliminated from an area, it may take thousands of years, and the right habitat, for them to return. 50% of the state forests in Maryland are being managed for harvesting of wood products. This leaves only 6% of the forested land, or 3% of the total land in Maryland, for recovery of many species of plants and animals on the brink of extinction. More state forests, as well as forests in private hands, need to be managed for biodiversity rather than for wood products.

Fragmentation of diminishing wildlife habitat by roads is one of the most severe environmental problems in Maryland. Our existing road system was built to accommodate automobiles with little consideration given to its effect on wildlife. By widening and improving roads without providing wildlife crossings, we are forcing thousands of animals to cross high-speed highways to get from one feeding or breeding area to another. The result is a growing volume of animals killed on highways each year.

Many states, as well as many foreign countries, have determined the importance of fixing the roads to stop the slaughter of animals on highways. Florida seems to be a leader in the US, and in the 1980s installed many underpasses on I-75 in South Florida which nearly eliminated vehicle collisions with the Florida panther. They found many other species using the underpasses including bobcats, deer, raccoons, bear and alligators. Currently, Florida is trying to identify other mitigating measures to create a "greenfrastructure" for wildlife across Florida.

The Florida program is very similar to the "green infrastructure" plan in Maryland. However, the Green Infrastructure Program in Maryland has no plans in place to fix the highways. If there are no plans to identify and fix locations where the green infrastructure intersects highways, the plan will simply lead animals to their death trying to cross over highways.

North Carolina is using infrared cameras, radio telemetry, and surveys of animal tracks to determine wildlife movement across roads in the state. They recognize a "clear need for management actions to reduce the incidence of vehicle-wildlife collisions for large mammals."

Arizona is constructing bridges over areas of high wildlife activity to allow animals to pass beneath their roads. Wyoming has provided wildlife fencing and access control on many miles of I-80 and I-25, and have installed a system for detecting deer movement and triggering flashing red lights on a state road.

The US is not unique in recognizing a requirement to improve roads for wildlife. There are 21 wildlife overpasses in Germany, 8 in Switzerland, 6 in France, and 4 in the Netherlands. Canada and Hungary have installed similar structures. Eleven European countries have now combined resources to investigate habitat fragmentation due to transportation infrastructure. The negative impacts on biodiversity created by roads, railroads and some waterways is a recognized consequence of building transportation networks without fully considering the impacts which include loss of habitat, barrier effects, noise and light disturbances and pollution.

While wildlife mortality on Maryland's highways is known to be high, there are few programs aimed at solving the problem. Highways should be constructed to allow wildlife an easy means of crossing over or under them, and this should be part of any good road building policy.

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