A study of forest fragmentation by a team of researchers at the University of Maine has found that the zoning system used by the state to protect winter habitat for deer is not an effective long-term strategy if the area surrounding the protected land is unregulated.
Erin Simons-Legaard, an assistant research professor of forest landscape modeling, used forest-harvest maps that document landscape change between 1975 and 2007 to evaluate the effects of timber harvesting on mature forest. The research area includes 36 percent of the deer-wintering areas zoned by the state in unorganized townships, where timber harvesting is limited.
“The zones have effectively done their job,” she said. “We didn’t see a lot of harvest incursion within the zones. But there was no carryover effect into the surrounding landscape. It had no effect on the larger landscape, in which deer have to move to get to the zoned areas. Just outside the zones, we saw the amount of mature softwood forest decline, a reduction in forest-patch size, and an increase in the distance between patches – all of what you get from habitat fragmentation.”
Of the 187 zoned areas she evaluated, Simons-Legaard found that 97 percent had at least some harvesting within the zoned boundaries, but in most cases, the area harvested was less than 25 percent of the zone. The reduction of mature conifer forest – which is the preferred deer winter habitat because it provides a buffer from wind and snow – was just 13 percent inside the zones. But the landscape outside the zones saw a 45 percent decline in mature conifer forest.
“What this tells us is that if your habitat-conservation strategy is focused on narrowly defined areas, it’s only going to get you so far,” she said. “If you’re interested in maintaining habitat connectivity region-wide, the current zoning system isn’t going to do much for you. It doesn’t protect connectivity between zoned areas. When you take a narrow view of habitat conservation, you’re going to get narrow outcomes.”
Rather than finding new areas to zone, Simons-Legaard recommends revisiting the currently zoned areas and reanalyzing them to determine whether deer are using them anymore. That will help to prioritize habitat conservation areas and to identify opportunities to expand zoned land. She also recommends regular monitoring of the habitat and its use by deer to better understand the long-term benefits of zoning. “Our analysis says that we can do this a little smarter if we take a second look at the zones we have and look at opportunities to work with individual landowners for expansion,” she said. “Some current[ly] zoned areas may be too small to be beneficial to deer, and some that are currently unoccupied may be unoccupied because they’re too small.”