A new report on the nation's ecosystems paints a grim picture.

There may be no streams left in the United States that are free from chemical contamination. And about one-fifth of animal species and one-sixth of plant types are at risk of extinction.

The report comes from the Heinz Center for Science, Economics and the Environment. It attempts to put together in one place the statistics about natural resources that had been spread among several federal agencies, including the Environmental Protection Agency and the Interior Department.

The report also proposes an objective set of ecological "indicators" about the nation's environmental health.

The study will be updated every five years.

A news release said that the report also found gaps in what is known about the nation's resources.

"Just as economic policies are informed through a set of key indicators ... we as a nation must have clear indicators of the condition of our ecosystems as a basis for shaping public policies and private sector initiatives," said William Clark, a professor at Harvard and chairman of the project.