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Biodiversity crisis grows deeper

Nature's Notebook

Connecticut is 60% forested, the 12th most forested state in the country, but it’s becoming a forest of largely mature trees. And that’s a problem because it contributes to a biodiversity crisis.

Without young forests, you start to lose important species, such as the Eastern bluebird, songbirds like the Chestnut-sided warbler, the native New England cottontail, plus the American woodcock.

“We’re becoming a forest that is pretty much mature trees,” said Jeffrey Ward, chief scientist at the forestry and horticulture department at the Connecticut Agricultural Experiment Station (CAES) in New Haven.

“It’s like a gated community in Florida. We don’t have that vitality. We don’t have young trees. Without them, we don’t have the biodiversity.”

Ward discussed biodiversity Saturday, May 14, at a forest-health lecture sponsored by Great Mountain Forest at the Shelter on Golf Drive in Norfolk, noting that in the last 50 years Connecticut has lost 90 percent of its young forests and close to 75 percent of medium-age forests.

The New England cottontail rabbit needs young forest because it’s the only place where it can compete with the Eastern cottontail, which is not native to New England. In 2006, the New England cottontail was considered for listing under the federal Endangered Species Act because of loss of habitat.

Ward addressed various pressures that contribute to a biodiversity crisis, ranging from climate change to the rise in the number of invasive insects to forest fragmentation that accompanies suburban development to the impact of excessive deer browsing that leads to the spread of invasive plant species.

Citing projections that show wetter winter and spring seasons, and little change in precipitation for the summer and fall seasons, Ward expects to possibly see more anthracnose, or leaf blight in the forest. With longer summers, he said there could be more infestations of the bronze birch borer that feeds on birch trees.

Last year, spongy moths, formerly called gypsy moths before the Entomological Society of America changed the name that contained an ethnic slur, defoliated large tracts of forest in Sharon.

“There’s a chance you’re going to see a significant defoliation from spongy moth again here this year,” Ward said, because they’re back in force.

The spongy moth was at the top of Ward’s list of 18 insects that pose risk to trees in the forest, and he said there are likely more examples on the way.

The Eastern hemlock is under attack by the Hemlock wooly adelgid, an East Asian insect that is killing the hemlocks.

“With a couple of warm winters,” Ward said, “you could lose a lot of hemlocks.”

The Emerald ash borer has decimated nearly all of the ash in the state, he said.

Ward listed the Asian long-horned beetle (ALB) as a future threat to maple, poplar and willow trees. He said efforts to eradicate the beetle in New York City, Chicago and Toronto have been effective, and that work is still underway in Worcester, Mass.

U.S. government efforts to control ALB in those cities resulted in dramatic changes.

“They come in and cut down every tree susceptible to ALB. Imagine losing all the maples along your street,” he said. “This would make the chestnut blight look like nothing.”

He labeled the American chestnut, the butternut, the elm, the American flowering dogwood, eastern hemlock, and American beech as functionally extinct.

“You can still find them but they are no longer part of the functioning ecosystem,” Ward said.

“The American chestnut was 10 to 25% of the trees in Connecticut before the blight. In the 1930s there would be one butternut in pretty much every acre. They’re gone,” he said.

Thirty years ago, the flowering dogwood was one of the most common understory trees in the state. No longer, he said. What’s more, the tree is a food source for 117 species of butterflies and moths.

“A brood of five Black-capped chickadees needs 6,000 to 9,000 caterpillars per year,” Ward said.

On the need for a younger forest, Ward pointed out that without harvesting trees the forest can’t produce a new generation that needs sunlight to grow. That includes red and white oak, paper and gray birch, yellow poplar, cherry, Atlantic white cedar and the pines, the sumacs and the aspens, among others.

Before the last few decades, Ward said, almost all housing development in Connecticut happened on abandoned farmland. Now, people are moving out into the woods, carving out chunks of one-acre lots in the forest.

“As you start cutting woods into little bits and pieces, species that need forest interior conditions aren’t going to have them. It isn’t just the footprint of the house and lawn. You have to go out 200 feet beyond that perimeter to gauge the impact,” he said.

A 15-acre development might amount to something like 200 acres, he said. The result is that when people move out into the woods, we don’t have the big blocks of forest anymore, like the 200-acre, 2,000-acre or 5,000-acre tracts.

Deer love suburban areas where there are nearby woods. Deer can rest in forest during the day and move into managed landscapes during dawn and dusk to browse on highly nutritious food in the form of lawns fertilized with nitrogen, bordered with flowers like the succulent Coleus. Homeowners also love to plant Barberry and Burning bush, two invasives. Barberry plants also harbor ticks: There are approximately 120 ticks per acre in a Barberry infested forest, compared to 10 per acre in one without the invasive.

If a homeowner plants an invasive species around the house, there’s a good chance that deer will carry its seed away to be further spread across the landscape.

Too many deer will  decimate the shrub layer in the forest, with a negative impact on shrub-nesting birds. Ward cited studies that show high deer populations correlated with low bird density. Deer also graze on herbaceous wildflowers, affecting the native pollinators, and they eat the seeds before they have a chance to develop.

In one study done at CAES of 566 samples of deer pellets, scientists found 11,512 individual germinants, and 70% of the seedlings were not native to the United States.

“We found Wineberry, Japanese honeysuckle and autumn olive. We had petunias coming out of deer pellets. We had green peppers coming out of deer pellets,” Ward said.

In another study of the extent of deer browsing, CAES scientists examined a 6-inch sugar maple, one of countless others like it found on the forest floor. They were curious about its age. After slicing it up and running their tests, they learned that the little stem of a tree was 17 years old. It had been chewed down year after year, waiting for its moment in the sun to grow.

 

John Coston, editor of The Lakeville Journal, is a member of Board of Trustees of Great Mountain Forest.

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