2012 Progress Report

Background for a Grassland: Why we burn

One of the difficulties of creating grasslands in the eastern United States is that most landscapes don’t want to be grasslands. With enough rainfall and rich soil, grasslands will give way to trees and shrubs, and eventually become a forest. So, in order to maintain grasslands, we reset the cycle, and that means a good fire.

We call this method a “prescribed burn”, in which we prescribe a time, usually early spring, to annually burn a section of the grassland, which removes invasive plants and woody vegetation. A section burned one year (one-third or one-fourth of the grassland) will be burned again three years later, allowing a mosaic of habitats to develop in the grassland. First year burns will have young, tender grasses and wildflowers by summer, and sections burned the previous year will have tall, mature grasses mixed with wildflowers and sapling trees or bushes. Sections burned a year prior to that will have trees and shrubs that overshadow the grasses, which we call “scrub habitat”. Those sections will be burned the following spring.

Prescribed burning isn’t new. It has long been used to maintain farmland, grassland and prairie, augmenting nature’s lightning storms, which set fire to dead grasses and trees, allowing the seeds of new grasses to grow. Native American tribes hunted for buffalo by intentionally burning large swaths of grasslands so tender new shoots would grow and attract their quarry to forage. Much of the grasslands in the eastern U.S. would not have been present by the time the colonists arrived in the 18th century, without prescribed burns.

And therein lies the problem. Grasses have evolved for thousands of years renewing their communities through burning: an “out with the old, in with the new” behavior. Today, however, large-scale burns are incompatible with population growth. Left to its own devices, land is consumed with thickets of invasive plants that push out native grasses and wildflowers, and the wildlife that feeds on them. Native grasslands must be managed in order to stay healthy, and that requires a good burn, which on Fishers Island requires coordination with the Fishers Island Fire Department (FIFD).

In 2010, when the need to rescue degrading habitat came to light, FIFD had annually used burns as a training exercise, but it was random in terms of timing and location. Now FIFD, coordinating with the Conservancy, implements the three-year burn plan, which includes areas to avoid due to ground bird nesting areas.

By Adam Mitchell, Associate Wildlife Biologist®
PhD Student, Department of Entomology and Wildlife Ecology, University of Delaware