Forest Health

Overview

Forests are critical to the health of the Chesapeake Bay. Large stands of trees protect clean water and air, provide habitat to wildlife and support the region’s economy. But human activities have altered the watershed’s forests, reducing tree cover and fragmenting forests that still exist. Conserving and expanding forest cover is a critical, cost-effective way to reduce pollution and restore the Bay.

Why are forests important?

Forests are critical to the health of the Chesapeake Bay. Large stands of trees perform ecological functions that can benefit all plants and animals, from cleaning our water and air to creating valuable habitat.

Protecting clean water

Forests act like giant sponges, keeping our rivers and streams clean and protecting our drinking water. Forests capture rainfall, trap polluted runoff and stabilize soils that might otherwise wash into waterways.

• Streamside forests, also known as riparian forest buffers, can reduce the amount of nutrient pollution entering waterways, sometimes by as much as 30 to 90 percent. Forests currently buffer about 60 percent of the streams and rivers that flow into the Bay.

• Mature trees have deep root systems that can hold soil in place, stabilizing streambanks and reducing erosion.

Protecting clean air

Trees don't just produce the oxygen we breathe: through a process known as attenuation, tree roots and leaves and forest soils can also absorb and trap the pollutants in our air.

• Forests can capture more than 85 percent of the nitrogen that falls onto them from the air, preventing it from flowing into our groundwater, rivers and streams.

• In urban areas, tree cover can lower summertime temperatures, counteracting the decline in air quality that can occur when pavement and buildings replace plants.

Creating habitat

Different types of forests provide food, shelter, nesting sites and safe migration paths for critters in the water and on land:

• “Interior” forest is habitat deep within the woods: a sheltered, secluded environment away from the influence of other land uses. The presence of interior forest is a good sign of woodland health, and provides the species that live there with the moderate temperatures and light levels they need to survive. Just 40 percent of Chesapeake forests can be considered interior habitat.

• Streamside forests shade the water that runs beneath their leafy canopies, maintaining cooler water temperatures and reducing stress on sensitive fish. Leaf litter, seeds and other plant materials fall into streams and form the foundation of the freshwater food chain, and fallen branches, logs and woody debris can create habitat for underwater critters.

• Standing dead trees, also known as snags, provide habitat to owls, woodpeckers, squirrels and other animals that nest in tree cavities. Insects, small mammals and birds can be found foraging and living among the decomposing logs, stumps and leaves on the forest floor.

Supporting the region's economy

Forests contribute billions of dollars each year to the economy by:

• protecting clean air and water,

• supplying wood and paper products,

• generating jobs and income,

• increasing property values,

• lowering residential and commercial energy use,

• improving physical and mental health, and

• providing opportunities for recreation.

Forestry is the second largest industry in Pennsylvania and Virginia and the fifth largest in Maryland. The forest industry supports many local cities and towns, providing 140,000 jobs, $6 billion in income and $22 billion in industry output to the Bay region’s economy each year.

Supporting outdoor hobbies and recreation

Forests provide us with places where we can reflect and experience natural beauty and solitude. Forests also foster outdoor recreation, through activities like hiking, biking, camping and bird-watching.

What does a healthy forest look like?

A healthy forest is a complex community of plants, animals and soil with multiple layers of vegetation, each of which performs a unique function. This diversity of structure allows forests to protect clean water and provide wildlife with a range of critical habitats.

• The top layer of the forest is known as the canopy. The canopy shades and protects the plants and animals below it, while intercepting and slowing rainfall.

• Below the canopy is a layer of smaller trees and shrubs known as the understory. Here, young trees begin to grow, replacing older trees as they die.

• Below the understory is the forest floor, where vines, grasses, mosses, worms, insects, fungi, bacteria and other small plants and animals can be found. Here, leaves, wood and other organic material decompose into a nutrient-rich soil that will feed other plants.

• The litter on the forest floor protects the underlying soil, which often contains more living biomass than what can be found above the ground.

How are forests harmed?

Human activities—including sprawling development and the introduction of invasive species—have altered the composition of forests across the Chesapeake Bay watershed, reducing tree cover and fragmenting those forests that still exist.

Historic deforestation

When Europeans arrived to the Bay region in the seventeenth century, they discovered diverse forests that stretched across 95 percent of the watershed. European settlers viewed the removal of these forests as integral to economic development, and European settlement had dramatic and long-lasting effects on the region’s forests and water quality.

By the late 1800s, 40 to 50 percent of the watershed’s forests had been cleared of trees, as land was repurposed for agriculture and trees were cut down for fuel, fencing and timber. Throughout the twentieth century, “new” forests grew up on abandoned farmland. But our forests are now more homogenous in age, size and species composition than before Europeans settled the region.

Development

Between 1982 and 1997, the Bay watershed lost more than 750,000 acres of forestland to development—a rate of about 100 acres per day. While this rate fell in 2006 to an estimated 70 acres per day, it remains unsustainable.

As trees have been replaced with roads, buildings, farms and houses, 60 percent of the watershed’s forests have been divided into disconnected fragments. These fragmented forests are less resilient to disturbances and more prone to negative influences like wildfires and invasive species.

Parcelization

Parcelization describes the breakup of large land ownerships into smaller ones. Over the past decade, the number of family forest owners in the Bay watershed has increased by nearly 25 percent—a rate of about 23,000 new family forest owners per year. But close to 70 percent of all family forest owners hold less than 10 acres of land.

The parcelization of forests often corresponds with a decline in the percentage of forestland that is managed for wildlife, timber, recreation or other uses; this increases the risk of fragmentation and conversion to other land uses.

Overabundant deer

In forests across the watershed, white-tailed deer have become an increasing threat to forest health. As forests are fragmented, deer have found food on farms and in suburban gardens and safe refuges in areas where hunting is prohibited. But locally high deer populations can harm forest growth and alter forest composition, as deer eat large amounts of seedlings and young trees and selectively browse for food.

Invasive plants, insects and diseases

Invasive plants are harmful to forests for several reasons. Invasive plants:

• grow and reproduce rapidly, killing and out-competing other species in the process,

• lower the quality of available food sources and shelter options for wildlife,

• eliminate the native host plants of insects, and

• compete with native plants for pollinators.

Kudzu, English ivy and Japanese honeysuckle are three invasive plants that have become permanent residents of Chesapeake forests.

Invasive pests and diseases can also alter forest conditions. Gypsy moths, emerald ash borers, chestnut blight, Dutch elm disease and beech bark disease have all had long-term, devastating impacts on the region’s forests.

How are forests being restored?

Retaining and expanding forests is a critical, cost-effective way to reduce pollution and restore the Bay. An investment in forests is an investment in clean water and air, and sustainable forestry will help address sprawling development, climate change and energy independence.

How you can help

To support forests in the Bay watershed, consider planting trees and shrubs to create more wildlife habitat. You can also choose and use native plants to support the plants and animals that have adapted to this region.