BOSTON — After more than 150 years of natural regrowth, forest cover is declining across all six New England states, threatening the region’s landscape and chipping away at a natural buffer against global warming.

That’s the conclusion of a study being released today by the Harvard Forest, Harvard University’s laboratory for ecological research.

The study said that after a spate of land clearing by European settlers, New England forests were allowed to grow back.

But that success is being reversed under the pressure of commercial development, industry use and invasive species. Less than 3 percent of New England’s 33 million acres of forest are permanently protected.

The report makes a series of recommendations, including long-term conservation efforts to protect at least 70 percent of the region, or 30 million acres, as forestland.

To learn more, go to Harvard Forest at http://harvardforest.fas.harvard.edu