U.S. Forest Service scientists released an assessment that shows forest land has expanded in northern states during the past century despite a 130-percent population jump and relentless environmental threats. At the same time, Forest Service researchers caution that threats to forests in the coming decades could undermine these gains.

According to the Forests of the Northern United States report, forest coverage in the United States has increased by 28 percent across the region that includes Minnesota, Iowa, Missouri, Wisconsin, Illinois, Indiana, Michigan, Ohio, West Virginia, Pennsylvania, Maryland, Delaware, New Jersey, New York, Connecticut, Rhode Island, Massachusetts, Vermont, New Hampshire and Maine.

Forested land currently accounts for 42 percent of the northern land area. Population in the region rose from 52 to 124 million people during the past 100 years, while northern forest coverage expanded from 134 to 172 million acres. Total U.S. forest land remained essentially unchanged during that time.

"While it's heartening to see our northern forests thriving in great times of change, we should also use this report as a reminder to remain vigilant about working together across all lands to make sure these positive trends continue," said U.S. Forest Service Chief Tom Tidwell.

"Forests have rebounded over the last century, but there are significant threats that could undo many of the gains. Forest Service research including a study released in 2010, have already indicated this. Our future research will delve more deeply into those threats."

The assessment is the first product of the Northern Forest Futures Project, a cooperative effort of the Forest Service, the Northeastern Area Association of State Foresters and the academic community. The project is examining how trends and choices may impact the landscapes of northern states. Partners in the cooperative hope ultimately the project influences decisions regarding the protection and sustainable management of public and private forests.

Outlined in the report are current conditions, recent trends, opportunities and threats affecting the most densely populated and forested part of the country. This information lays the groundwork for a 50-year outlook on northern forests, which the Forest Service is expected to release in 2013.

"The Northern Forests Futures Project will give landowners across the entire spectrum, from industry to states to non-government organizations and concerned residents, the knowledge they need to develop strategies for sustaining the forests that dominate our landscape and our history," according to Michael T. Rains, Director of the Northern Research Station.

The report shows that Pennsylvania, Michigan, New York, West Virginia and Maine have the greatest total volume of timber among northern states - more than 20 billion cubic feet each. Massachusetts, Maryland, New Hampshire, Vermont, Connecticut and West Virginia have the highest average volume per acre of timberland-more than 1,900 cubic feet per acre.

These trees benefit rural and urban communities by protecting soil from erosion, reducing energy consumption, collecting carbon emissions and providing clean water. Forty-eight percent of the North's water supply originates on the forests that cover 42 percent of the land.

In its economic evaluation, the northern forest assessment states that about 441,000 people work in the forestry, logging, wood products, and pulp and paper industries - accounting for about 40 percent of all U.S. jobs in these sectors.

Forest Service northern forest projections in 2013 are almost certain to show that future growth and sustainment is not guaranteed.

Invasive plants, animals, and disease threaten forest health. Invasive insects, such as the gypsy moth, and diseases, such as Dutch elm and chestnut blight, have afflicted northern forests for more than 70 years.

More recent arrivals, including the emerald ash borer, Asian longhorned beetle and hemlock woolly adelgid, have devastated some areas. And a recent Forest Service study also showed that urban development has contributed to a decline in tree coverage in U.S. cities at a rate of about 4 million trees per year.

Over the next year, Forest Service scientists will analyze how future forest conditions are likely to change over the next five decades. Those forecasts will consider how alternative economic, management, and climate scenarios are likely to affect forest conditions and the lives of people in the North.

The mission of the U.S. Forest Service is to sustain the health, diversity, and productivity of the nation's forests and grasslands to meet the needs of present and future generations. Recreational activities on our lands contribute $14.5 billion annually to the U.S. economy. The agency manages 193 million acres of public land, provides assistance to state and private landowners, and maintains the largest forestry research organization in the world.

USDA works with state and local governments and private landowners to conserve and protect our nation's natural resources - helping preserve our land, and clean our air and water. President Obama launched the America's Great Outdoors initiative in 2010 to foster a 21st century approach to conservation that is designed by and accomplished in partnership with the American people.

During the past two years, USDA's conservation agencies-the U.S. Forest Service, the Natural Resources Conservation Service, and the Farm Service Agency-have delivered technical assistance and implemented restoration practices on public and private lands. We are working to better target conservation investments: embracing locally driven conservation and entering partnerships that focus on large, landscape-scale conservation.