Deer Overpopulation a Threat to Forest Growth, Researchers Say

Rise in deer population and their grazing habits prevent forests from maturing, researchers have found.

The study, conducted by researchers at Cornell University, found that deer prefer seeds of native woody plants and reject invasive ones. This selective eating leads to loss of native vegetation and helps foreign plants take over forest land.

Grasses establish themselves in a piece of land. As the forest grows, Small herbs and shrubs replace grasses. Later, woody plants and trees take over the area. Researchers have now found that deer prevent the growth of woody plants.

"Deer are slowing down forest succession or natural establishment. In fact, the deer are preventing forests from establishing," said Anurag Agrawal, Cornell professor of ecology and evolutionary biology, a co-author on the paper, according to a news release.

The study was conducted on Cornell land near Freese Road in Ithaca. The deer density in the region is 39 animals per square kilometer, which is about ten times higher than the deer density in the 1700s.

Researchers obtained soil cores from both inside and outside of "deer exclosures." They found that soil outside the exclosure had more foreign seeds than the soil inside the fenced area.

"It's obvious that the deer are affecting the above-ground species, but it's like an iceberg. There are major effects below the soil surface. We are seeing a divergence of seeds contained within the soil from what should be there," said Antonio DiTommaso, Cornell associate professor of weed ecology and management. "We are not seeing the seeds of woody plants. Instead, we're seeing an escalation of non-native seed and the virtual elimination of woody plant seeds."

The study," Deer Browsing Delays Succession by Altering Aboveground Vegetation and Belowground Seed Banks," is published in the journal PLOS One.

A Bloomberg article published in 2012 reported that overpopulation of deer has harmed forests, farms and even human health. Another article in Wall Street Journal discussed the negative impact of increase in wildlife population in America.