ANNAPOLIS – After a drought, a hurricane and an abnormally wet year, the Chesapeake Bay has shown remarkable resilience, scientists say, but population and climate change pressures may reduce the estuary’s ability to bounce back.
“Estuaries are resilient by nature,” said Victor Kennedy, a professor at the University of Maryland’s Center for Environmental Science. But, “if human beings stress a system, then, with additional stress from climate extremes, you’ll see the loss of some species.”
Hurricane Isabel’s winds pummeled shores in September amid a yearlong deluge that washed pollution and sediment into the bay. This came on the heels of a two-year drought that inhibited freshwater fish spawning and allowed salt-water-loving oyster diseases to ravage a species on the brink of collapse.
Despite these conditions, good news emerged this fall.
Underwater grasses measured last fall reached the highest level since record keeping began in the 1970s and juvenile striped bass, or “rockfish,” populations surged to more than twice the long-term average this year. Drought helps underwater grasses escape runoff, and deluge helps striped bass spawn.
Yet recent climatic fluctuations are only a small part of long-term trends that show a deeper and warmer bay and the likelihood of lasting environmental damage.
The bay’s waters rose by one foot over the last 70 years, and the rise has accelerated with global warming. The bay may add another 8 inches by 2030, said Donald Boesch, the center’s president.
The average global temperature rose by 1 degree Fahrenheit during the 20th century. In North America, the temperature is expected to rise between 2 and 13 degrees in the next 100 years, said Benjamin Preston, a senior researcher at the Pew Center on Global Climate Change, a nonprofit and nonpartisan climate study organization.
Rising waters drown marshlands that provide shelter to blue crabs and juvenile fish. Floods exacerbate this problem by burying the bay in sediment and pollutants.
Rising temperatures spur the northward migration of many species that prefer the bay’s more typical climate.
Higher temperature also depletes oxygen. Warmer water inherently holds less oxygen and spurs growth of phytoplankton and algae that further starve the water of oxygen when they die.
Some scientists have even suggested that the East Coast must brace for more frequent and powerful hurricanes spawned by climate change, a position still controversial among scientists, Preston said.
This century, the temperature of the bay may come to resemble that of the North Carolina Sound. If that happens, soft shell clams would die off and pink shrimp – not native to the bay – would flourish, Kennedy said.
Scientists from the National Oceanic and Atmospheric Administration and the Chesapeake Bay program concurred with these projections in interviews.
Yet their overarching concern is the convergence of these changes with human pressures.
Population in the bay’s watershed, an area extending from western New York to southern Virginia, is expected to jump by 20 percent by 2030, according to the Chesapeake Bay Program, a nonpartisan bay-research partnership between bay states and the federal government.
Scientists attribute much of the bay’s woes to the spike in population that occurred after the 1950s that coincided with the “green revolution” or burgeoning use of commercial fertilizers that pollute the bay.
Development since colonial times has stripped the watershed of its forests, which trap sediments and pollutants.
And pollutants from industry and transportation are linked to the greenhouse effect where heat from the sun is trapped in the earth’s atmosphere, which drives global warming.
Because of human development “the bay is much less resilient than it was 50 years ago,” Boesch said.
Protecting the bay is an uphill fight, said Boesch. “Climate change makes the hill a little bit steeper.”