Where the Deer Are

Deer overpopulation in the Philadelphia suburbs is not new. While some people would argue that regional development has decimated the white tail deer’s natural habitat, West Chester geography department chair Dr. Joan Welch posits that we’ve actually increased their habitat as we break up larger forests into smaller woods.

Welch has spent the past 10 years gathering and analyzing data on the impact deer have on our ecosystem. Her data indicates that our old-growth forests are much healthier when deer are excluded and prevented from eating plants and young trees. Her study took place at Warwick County Park near Elverson, Pa., where county officials wanted to examine the impact of organized hunting of deer in the park.

“The park is unique,” Welch notes. “Its north-facing contiguous woods is one of the few interior forest habitats in Chester County, with another being the big woods in French Creek.”

In 1996, Welch and some of her students, including Jacquelyn Arnold ’96, enclosed six 20 x 20-meter sections of woods at random locations in the park, as well as control sites. They took an initial inventory of the woody plant species in the control sites and the innermost 4 x 4-meter segment of those “exclosures.” She and the students then inventoried the plants annually.

An opportunistic species (one that adapts relatively easily to changing conditions), deer are “edge animals” that rely on forests for cover, but prefer to browse at the edges of fields – and around Chester County, those fields have often become lawns in newer residential neighborhoods.

Homeowners lose some landscaping to deer damage, but the impact deer have on destroying the plants, shrubs and saplings in the lower levels of old-growth forests – the understory – is a far greater threat over the long run.

Why are old-growth forests important? “Forests are the number-one flood control element in this region,” explains Welch. “They prevent excessive overland flow and provide storm water management. They cleanse the ground water for us.”

For Chester County, Welch’s research will impact forest regeneration and health, providing data to protect and enhance important and limited open space resources.

The study indicated that “there has been notable recovery of the understory woody plants at Warwick County Park since the deer exclosures were built and hunting was implemented as a forest resource management plan. The recovery in the deer exclosures appears to be ahead of that for the control sites.… Species diversity is higher in the exclosures than in the control sites.”

Among scientists studying healthy ecosystems, says Welch, “We are beginning to appreciate that diversity is stability.”

“Pennsylvania is blessed with a wealth of native plants and animals, and we have a duty to conserve these treasured natural resources for future generations,” Governor Rendell said, in announcing the grants.