The health of the Chesapeake has improved slightly since last year, although only part of the credit for the change goes to management actions, according to the annual “State of the Bay” report compiled by the Chesapeake Bay Foundation.

On a 100-point scale, the environmental group this year put the Bay’s health at 28, one point better than it awarded the Chesapeake last year.

The score was based on an average of 13 different indicators, which paint a mixed picture for the Bay. While efforts to bring back the striped bass have been successful, and oyster restoration efforts are being stepped up, trouble looms for wetlands and blue crabs.

And, part of the reason for the improvement goes to Mother Nature — drought conditions the past year helped to improve water quality because fewer nutrients are flushed into the Bay during dry years.

“It’s the good, the bad and the drought,” summed up Mike Hirshfield, CBF vice president for resource protection.

Hirshfield said credit for the improvement was “about split down the middle” between Mother Nature and management. “The rockfish, oysters and shad, I would give the credit to management decisions. The declines in wetlands and crabs I would give to management decisions. And the rest is Mother Nature.”

While management actions have helped some resources, the CBF said lack of management action was adding pressure on blue crabs, the Bay’s most valuable fishery, on two fronts: fishing pressure has increased and critical grass habitats are declining.

Likewise, the group said wetlands are declining because Virginia officials have not taken action to close a loophole that has led to the draining of more than 2,000 acres of wetlands in the last year, with thousands more acres in jeopardy.

On CBF’s scale, a score of 100 would be a hypothetical “unspoiled” Bay much like John Smith might have found in the early 1600s. Although this score is considered unachievable, CBF said a rating in the 70s could eventually be attained.

The organization also released an ambitious restoration plan that it said could return the Bay to a score of about 50 by 2010. The plan called for nutrient reductions of 50 percent, and stepped-up programs to restore oysters, wetlands, forested stream buffers and other resources.

To come up with its score, the CBF compares the current status of 13 indicators — various aspects of water quality, habitat and resources — with what their condition is thought to have been nearly 400 years ago. For example, Bay grasses get a score of 12 because they are thought to cover about 12 percent of their historic acreage in the Chesapeake.

Because John Smith and his comrades didn’t collect comprehensive information, CBF admits the index is subjective, yet still reflects the best professional judgment of its scientists.

The CBF estimates that the Bay hit its low point in the early 1980s — a time when the abundance of Bay grasses and striped bass were at record lows and no nutrient reduction efforts were under way. At that point, the organization would have scored the Bay about 23.

“On the balance, the Bay is in somewhat better shape than it was 15 years ago,” said CBF President William Baker. “But for every success story, like rockfish, there are continued declines, like the loss of more than 60 percent of Tangier Sound’s underwater grasses in just seven years.

“We’ll never see a Bay that is as pristine as that which John Smith saw,” he added, “but we believe that if citizens of the watershed demand the Bay’s restoration and pitch in, and if the Bay Program commits to reaching these ambitious goals, we can take the Bay’s health to at least a score of 50 by the year 2010.”