Ecologists Revive a Dwindling Tree Population and Steel the Landscape Against Fire
Take a walk around the interior of the Davis Mountains Preserve and you're likely to hear a symphony of noises you might not expect to find in the West Texas desert: A babbling creek and a chorus of tree-dwelling birds. In the dense forest of evergreens you might think you’ve landed in New England or the Pacific Northwest. But this is a unique microclimate that scientists call a Sky Island Ecosystem.
As Charlotte Reemts describes it, "The Davis Mountains are biological islands of diversity in the desert sea."
Reemts is a research and monitoring ecologist for the Texas Chapter of the Nature Conservancy. She oversees a team charged with preserving some 33,000 acres of breathtaking terrain not far from the McDonald Observatory in Fort Davis. Her current project involves saving the last major population of Ponderosa Pine trees in Texas.
According to Reemts, the decline of this Southern Ponderosa population was in large part due to natural environmental changes: "Several thousand years the pine was much more extensive. As the climate warmed and dried, the Ponderosa and a lot other species retreated into these mountains because it's the only place in Texas that is cool and wet enough for them to survive."
Walk a little deeper into the cool, wet canyons of the preserve and the sounds of creeks and birds may give way to a whole other set of surprising noises: chainsaws.
These chainsaws are manned by contractors hired by Reemts' team to target certain problematic species of trees in a strategy called thinning. It's designed to give the Ponderosa Pine a fighting chance in these mountains by fending off plants that may give young pines too much competition for resources. Living in a thinned forest also means diseases and insects find it harder to move around.
But why else has a plant that has become so dominant in other parts of the American West had such a hard time succeeding in Texas? One of the greatest reason is that the tree can't use one of it's most sophisticated adaptions: heat-resistance.
"Naturally, most of the Ponderosa Pine seedlings get establish after a fire," says Reemts, "That actually sterilizes the soil and it takes a long time for the other vegetation to grow."
She says that low-level brush fires that used to be a natural part of life in West Texas have disappeared as cattle have been introduced and grazed massive quantities of grass.
"The historical fire regime was having fairly cool, surface-only fire two-to-three times a decades" says Reemts.
According to her, the cattle "essentially stopped" natural fire conditions.
Without grass, trees and bushes of every size are left to grow as competition for the Ponderosa, and fuel for major wildfires.
"With higher tree density comes risk of a very different kind of fire," warns Reemts, "The fires can get up into the canopies of the tree and you get much higher severity."
In simple terms, thinning projects are designed as an attempt to reset the ecological conditions back to the days before Westward American expansion into Chihuahuan Desert.
This means setting the right type of fire again, in what ecologists refer to as, 'prescribed burns.'
Jason Wrinkle is a leading-fire expert for the Nature Conservancy who has been both fighting, and setting, fires in the Davis Mountains Preserve. He says that he has seen firsthand that thinning efforts designed to save the Ponderosa Pine, also have the added benefit of curbing the sort of unnatural fires that have wreaked havoc on the West Texas landscape over the part few years.
Only 5,000 acres of the preserve were left unscathed in the fires of 2011 and 2012, and according to Wrinkle, "in most of those areas, we had utilized prescribed fires."
Restoration efforts in the Davis Mountains are set to increase. The Nature Conservancy has received a major grant from the Doris Duke Charitable Foundation that will make it possible to apply thinning on an even larger scale.
The hope is that both people, and the Ponderosa Pine, will get to continue to enjoy the splendor of the Davis Mountains Sky Island for years to come.
-- Ryan Lentini