Conservation Concepts
With Charles Bier

Dear Charles,

Pennsylvania is a very green state on the whole, with more than half the area covered in forests. That is quite a conservation accomplishment, but what is the biggest issue to keeping our forests?

Sincerely,
Gretchen

Dear Gretchen,

The health and viability of Pennsylvania’s forests will face many challenges over the next century and it is difficult to pick the top issue out of: global warming, excessive deer populations, acid deposition, impacts by exotic species and others. However, one of the most important issues relates to all the others, and that is forest fragmentation.

Fragmentation is simply the division of habitat areas into smaller and smaller units. This is an important concept in conservation theory because as habitats are reduced in size, and especially when they become bounded by uninhabitable zones, ecological viability and suitability for living species declines. For example, 10 one-hundred acre patches of forest, each bounded by four-lane highways, do not provide the same ecological function, habitat or conservation value as a single one-thousand acre patch of continuous forest. So patch size and the condition of adjacent areas are of concern in maintaining biodiversity and ecological integrity.

Remember, forests are not simply groups of trees, but exist as ecosystems with thousands of species of plants, animals, fungi and more, all with their own life-ways and requirements for survival. A pair of wood thrush might only require a dozen acres of forest for nesting, while the northern goshawks require more than one thousand acres. So forest patch size matters and the examples given are only for a single pair of each of those species. Conserving enough forest to provide habitat for viable wildlife populations is ultimately the real conservation goal. For example, forest interior birds require thousands of acres of good habitat to address threat factors. One study shows that smaller forest patches allow some nest predators, which mostly travel into forests to the depth of only one to two football fields, to have significant impact on nesting success. Other conservation problems, such as high white-tailed deer density and invasive exotic species, increase with small patch size and forest fragmentation.

The type of fragmentation is another aspect of this concept. The condition, width and longevity of fragmenting features are important. A forest clearcut or a tornado blowdown are drastic albeit temporary, while a multi-lane concrete super-highway with speeding traffic presents more drastic threats. While some wildlife and the seeds of certain forest plants might fly across a highway to another forest patch, it has been shown that there are ground dwelling forest species that will not cross such a barrier. One study shows that this affects the genetic flow between adjacent colonies of forest ground beetles and, therefore, is a conservation concern.
Conservationists are turning to landscape level planning and protection. Large landscapes and watersheds linked through a network of effective corridors are key to successful biodiversity stewardship. As our native species and their ecosystems are taxed by looming stresses like global warming, scientists believe that our largest habitats and landscapes will be the most resilient.

Thanks for your question, and remember: Think Big!

Sincerely,
Charles Bier
Senior Conservation Scientist

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