The Nature Conservancy began work on its Medicine Lots property in West Tisbury to prepare for its habitat conservation, where rare wildlife and “frost bottoms” coexist. The project to make the area into a sparse post oak savannah is anticipated to be completed in the coming weeks, after which it will be maintained with rotational mowing.
The Medicine Lots is an area the conservancy acquired in 2013 to preserve the wildlife and habitat in the area. Mike Whittemore, the Island’s land steward for the conservancy, said the property’s location is “very important.” The property is between the “ecologically significant” Manuel F. Correllus State Forest and Long Point Wildlife Refuge. “This adds connectivity,” Whittemore said. “It’s only 97 acres, but it has 19 rare species, state-listed species, so it’s a real biological hotspot.”
According to Whittmore, many of the rare species that live in the area include moths, butterflies, and whippoorwill, a bird species that has been experiencing a population decline. Many of the moths like to stay around the scrub oak on the property.
Island naturalist Matt Pelikan said the moth species at the Medicine Lots associate with scrub oak, such as barrens dagger moth, Melsheimer’s sack-bearer, and the sandplain heterocampa, which are all threatened by habitat loss and other issues according to the Massachusetts Natural Heritage and Endangered Species Program.
“There are quite a few others, many of them listed under state Endangered Species Act,” Pelikan said. “Because scrub oak barren is a rare habitat in our region, a lot of insects that associate with it are rare. So preservation and appropriate management of the scrub oak at the Medicine Lots is important in order to preserve habitat for these rare moths.”
The oak in the area contributes to the habitat’s importance. Walking down the trail, Whittemore pointed out the gnarled oaks surrounding the area and oak stools, which are trees that experienced being cut down and burned numerous times. This process shapes the tree to look like smaller trees conjoined around a stump.
“That is a legacy of fire,” Whittemore said. “There has been fire on this landscape for over a thousand years and that really adds to the processes that keeps this habitat rare and fertile.”
The different oak species, like post and white, make up layers for the area. In an area where understory mowing was taking place, workers also removed some trees to open up the canopy and create more open landscapes. “We’re actually keeping a lot of the post oaks and some of the white oaks,” Whittemore said. “Post oak is actually on the very northern tip of its range here. Very uncommon in Massachusetts.”
Whittemore said while removing trees may seem “counterintuitive,” the change to the environment has made it a necessary part. He said the property was a “fire-adapted disturbance-dependent habitat” and suppression of fire on the Island took away the prevalent part of the habitat. “Since we aren’t able to do fires here, we have to clear the trees and open it up in a different way using mechanical disturbance,” he said.
Maintenance through controlled burns is done on other conservancy areas; private properties near the Medicine Lots makes using fire a liability issue. This is especially true because of how flammable scrub oak is.
The disturbance is a two-stage process. The first is a “heavy-duty restoration” phase followed by subtle maintenance, particularly keeping the scrub oak in the area that many species rely on. Whittemore said the work was being done during the “dormant season” to minimize disturbances to the moths, which return during June and July.
Another piece of the habitat that the conservancy wants to protect is the frost bottom, which are rare low-lying areas formed by glaciers with microclimates that increase local biodiversity. “[The Medicine Lots] is what we would say is the headwaters of this ancient, glacial meltwater channel,” Whittemore said. “This is the very tip of the frost bottom and it runs all the way down to Edgartown Great Pond.”
The frost bottom was not easy to identify with a cursory glance. There was an area with a subtle decline that just looked like a hill. However, a temperature difference of up to 15°F could be felt at the bottom of the decline, a chill that can be experienced even in the summer. Whittemore said scrub oaks can grow well in frost bottom areas. This provides a microclimate where scrub oak can grow while keeping a temperature ideal for moths. Whittemore said there are around a dozen frost bottom areas on the Island, but very few are undeveloped like the Medicine Lots.
Not managing the property leads to tree species like pitch pines diminishing the effects of frost bottoms and can “shade out” other vegetation, according to Whittemore. Leaving the property unkempt would worsen the biodiversity over time, and moths and whippoorwill aren’t the only species in the area. Field mice and red-tailed hawks are some of the other critters that are in the area. Whittemore said the Medicine Lots is also considered “ancient woodlands” on Martha’s Vineyard and it is uncertain when management last took place.
“We’re trying to take out as many trees as possible so that it’s an open habitat and scrub oak can flourish,” Whittemore said, adding that the removal is done in a way to minimize the amount of carbon that enters the soil. “However, we want different age trees as well to create a mosaic of sand plain barrens habitat. It’s not all about grasslands, it’s not about scrublands.”
When asked about how climate change impacts the property and the project, Whittemore pointed out that many of the species on the Medicine Lots are at the tip of their northern range.
“If we can keep this habitat intact and make it suitable for them and better for them, we think that they’re going to increase here,” Whittemore said. “We think that we’re adapting to climate change by influencing what vegetation can stay and what we’re taking out right now. Of course, that translates to the rare moths that use this habitat.”