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Senate Hearing: Non-Native, Invasive Plant Species Ecologically Castrating The Landscape, But There Is A Solution

The Senate Agriculture and Rural Affairs Committee Tuesday heard from a series of presenters covering issues related to invasive and native species.

One highlight of the hearing was a presentation by Dr. Doug Tallamy of the Department of Entomology & Applied Ecology at the University of Delaware who outlined how homeowners and landowners have a major role to play in strengthening natural diversity in our landscapes so they can better support wildlife, pollinators and humans.

“We have a basic problem, not just here in Pennsylvania but everywhere. As we have expanded the human footprint, we’re destroying the natural world. We used to think that was OK because there was a lot of nature, but there’s not a lot of nature any more.

“If we destroy the natural world, humans will not persist on this planet. We absolutely need it, but there is a solution,” said Tallamy. “We have to learn how to coexist with nature where we live, work and farm.

“Nature is a series of specialized relationships, especially as it relates to food sources and it always starts with plants,” he said.

Tallamy used the Carolina Chickadees as an example of these specialized relationships.

He said most people believe they are seed eaters and that is part of their relationship with plants, but when they are reproducing they feed their young insects because young Chickadees cannot eat seeds.

He explained most of those insects are caterpillars and reproducing Chickadees are not the exception. Most of the bird species feed their young insects and most of those insects are caterpillars.

“The point here is you cannot have breeding birds in a landscape that does not have enough caterpillars,” said Tallamy. “96 percent of birds in North America are rearing their young on insects and not seeds.”

He said it’s simple-- no insects, no baby birds.

Based on a 3-hour survey in his backyard, Tallamy documented Chickadees bringing back 17 species of caterpillars to a nest to feed their young. They foraged the caterpillars within 50 meters of their nest in his yard.

He has counted up to 877 species of caterpillars in his yard to support bird reproduction there.

“The point is diversity creates stability in the ecosystem” and the food web, so that regardless of the weather or drought conditions, there will be enough caterpillars to support breeding birds.

A Chickadee pair brings 390-570 caterpillars to the nest per day to feed their young and they do that for 16 days before the young fledge which means 6,240 to 9,120 caterpillars per season per nest.

“If we want to have birds where humans are we have to have the landscapes that generate the insect life and caterpillars to support them,” said Tallamy.

He noted Chickadees are tiny birds-- about a third of an ounce, 4 pennies worth-- and bigger birds and the diverse mixture of species people prefer require much more food.

Taking the specialized relationships one step further, Tallamy explained, 90 percent of the insects that eat plants can develop and reproduce only on the plants with which they share an evolutionary history because they have developed the techniques and adaptations to eat those plants.

To explain this kind of relationship, he used the Monarch butterfly as an example.

Tallamy said the Monarch caterpillar is a milkweed specialist. The milkweed plant is protected from being eaten by its white, latex sap. Monarch caterpillars, however, developed a specialized approach to eating the milkweed leaves without having its mouth glued shut by the sap.

The down side of specialization, he said, is now milkweeds are all Monarchs can eat. If we take milkweeds out of our landscapes, like we have in so many places, we lose the Monarchs. There has been a 96.4 percent decline in Monarchs since 1976 because we have eliminated their food supply, Tallamy explained.

Because pound for pound there is twice as much protein in insects as there is in beef, insects are critical parts of most of the food webs in nature, including wildlife as diverse as toads and frogs, red foxes and even black bears which rely on insects for a major part of their diet.

Tallamy said we are losing insects species populations around the world, so it is not just a local problem. Insect populations have already declined 45 percent globally since 1974.

He said because we have lost insect populations, 432 species or one-third of North American birds are at risk of extinction and 46 species have lost half of their population. Estimates are there are 1.5 billion fewer breeding birds compared to 40 years ago.

“We have 3,300 species of plants that have come from someplace else invading our landscape,” said Tallamy. A third of the plants in our fields and yards are invasive species and they simply do not support the insects and caterpillars needed to support wildlife and us. They haven’t developed the specialize relationships they need.

As an example, he counted 19 species and 410 caterpillars around the base of a native white oak (not even the entire tree) on one day in July. Black cherry, same thing-- 14 species and 239 caterpillars.

He said this is the natural relationship between native trees and insects and there is no damage to the tree.

Compare that to the Asian Callery pear tree of about the same age that many people plant because they look nice-- there was 1 species of caterpillar and 1 caterpillar. Same thing for non-native burning bush-- 1 species, 2 caterpillars.

Tallamy said another issue with non-native and invasive species is “biological pollution” where these species “ecologically castrate” all the land around them by spreading beyond their initial planting sites to neighboring areas.

Tallamy said we don’t have to guess any more what kinds of trees and plants we should populate our landscapes with to support insects, wildlife and diversity.

He helped develop a tool with the National Wildlife Federation property owners can plant to support wildlife -- Native Plant Finder or the Audubon Society’s Plants for Birds webpages.

Tallamy said there are real consequences from the way we landscape our yards.

“How many species do we need to preserve? We need all of them because they produce the ecosystem services that support humans,” said Tallamy. “We have already degraded the ability of the planet to support humans by 60 percent. That’s the same as taking planet Earth and shrinking it by 60 percent.”

Tallamy said we can’t just rely on parks and preserves to maintain our diversity because they are too isolated. “That’s where nature is huddling right now, but they are not sustainable, they are too small. This has got to happen on private property.

“To restore nature’s relationships, we must raise the bar for what we ask our landscapes to do: support life, sequester carbon, clean and manage water, enrich soil, support pollinators by planting the right plants,” said Tallamy. “They can’t just be pretty.”

“We are not talking about good land stewardship, we are talking about essential land stewardship,” added Tallamy. If we lose our pollinators, it will not only hurt agriculture, but also the 80 to 90 percent of the plants that depend on pollinators to survive.

“If we think about plants only as decorations that equals ecological destruction,” said Tallamy. We need to think about plants as supporting nature and protecting our watershed so they contribute to ecological restoration.

Dr. Tallamy has published a book-- Bringing Nature Home-- on native gardening and biodiversity outlining similar points made in his presentation only in more detail.

Click Here to watch a video of the hearing. Dr. Tallamy’s presentation is first. Also making presentations were--

-- Dr. John Wallace, Penn State Extension Weed Crop Specialist;

-- Ruth Welliver, Director Bureau of Plant Industry, PA Dept. of Agriculture;

-- Lydia Martin, Director of Education, Lancaster County Conservancy;

-- Wendy Brister, Owner/Operator Harvey’s Garden; and

-- Greg Wilson, Conservationist, Lancaster County, who pointed out Warwick Township adopted an ordinance requiring property owners to landscape with 75 percent native species.

Sen. Elder Vogel (R-Beaver) serves as Majority Chair of the Senate Agriculture Committee, and can be contacted by sending email to: evogel@pasen.gov. Sen. Judy Schwank (D-Berks) serves as Minority Chair and can be contacted by sending email to: SenatorSchwank@pasenate.com.

(Photo: Monarch caterpillar, Chickadee.)

Native Plant Resources

There are lots of resources available to help property owners landscape with native plants, including--

-- DCNR Landscaping With Native Plants

-- Game Commission: Common Beneficial Plants Found In Wildlife Habitat

-- U.S. Fish & Wildlife Service: Native Plants For Wildlife Habitat And Conservation Landscaping

-- Chesapeake Bay Sustainable Landscape Professional Directory

-- Brandywine Conservancy: Forested Riparian Buffer Planting Guide

-- Audubon PA: Bird Habitat Recognition Program

-- National Audubon: Native Plants Database

-- Xerces Society For Invertebrate Conservation

-- Gardening For Butterflies: Penn State Extension