Historians say the Chesapeake Bay has changed since Capt. John Smith first landed at Jamestown four centuries ago.
And scientists say it will change again by the end of this one as a rising, warming ocean with more acidic waters carves out a different estuary and disrupts the huge diversity of marine life that depends on it.
"It will be quite a bit different," said Robert Latour, fisheries scientist at the Virginia Institute of Marine Science in Gloucester Point. "I imagine the coastline will be a little bit different — some projections put the Florida Keys underwater in 100 years, and we're pretty low-lying. In the fish populations, there will be winners and losers."
The bay is a vital space for numerous spawning species, a nursery for others and an important migratory route for countless more. Latour suspects native oysters, already decimated by overfishing and disease, could be hard-hit. And iconic blue crabs, once plentiful, could become scarce.
"We're starting to see blue crabs moving north in areas that we hadn't historically associated with them," Latour said. "So there's been a general shift in fishes, too."
But the bay is just one example, scientists say, of how a warming Earth will have real impacts at the local level. And it illustrates the message behind a new report issued this week by the U.N. Intergovernmental Panel on Climate Change. The report builds on earlier ones with more sophisticated and comprehensive science, and identifies the populations and places at risk: everyone, everywhere.
"The report concludes that people, societies and ecosystems are vulnerable around the world," Chris Field, co-chairman of the working group behind the study, said in a statement. "But with different vulnerability in different places."
According to the report's summary for policymakers, climate change isn't something coming down the pike; it's already here on every continent and in every ocean. Experts cite wildfires in the western U.S., record rains in England, extreme heat waves and droughts, changes in wind patterns, stronger coastal storms and cyclones.
And most of the increase in global average temperatures, the summary says, is "very likely" the result of the dramatic uptick in human-caused greenhouse gases that began with the Industrial Revolution.
The IPCC says the world, in many cases, is "ill-prepared for risks from a changing climate" and urges "smart actions" now to decrease those risks: curb emissions, mitigate the inevitable damage and learn to adapt to a rapidly changing world.
"Climate-change adaptation is not an exotic agenda that has never been tried," Field said. "Governments, firms and communities around the world are building experience with adaptation. This experience forms a starting point for bolder, more ambitious adaptations."
The clarion call comes hard on the heels of the report's clanging alarm bells, including:
•Concentrations of carbon dioxide and methane in the atmosphere in 2005 exceeded by far the natural range over the last 650,000 years.
•Eleven of the last 12 years (1995-2006) rank among the 12 warmest years since record-keeping began in 1850.
•More intense and longer droughts over wide areas since the 1970s, particularly in the tropics and subtropics.
•More frequent heavy rains over most land areas.
•Widespread changes in extreme temperatures over the last 50 years — with fewer cold days, cold nights and frost, and more frequent hot days, hot nights and heat waves.
•More intense tropical cyclone activity in the North Atlantic since about 1970.
As the planet warms, the report says the risks to mankind increase, including crop failures, a drop in gross domestic product, increasing poverty and hunger, violent conflicts, the loss of infrastructure and coastal communities and increases in food- and water-borne diseases.
The report also claims a "higher confidence" in its projections for continuing changes in warming, wind patterns, precipitation and ice:
•Greater warming over land and at most high northern latitudes, and less over the Southern Ocean and parts of the North Atlantic.
•Snow cover contracting, and widespread increases in permafrost thaw.
•Sea ice shrinking in both the Arctic and Antarctic, with late-summer sea ice in the Arctic disappearing almost entirely by 2100.
•More frequent heat extremes, heat waves and heavy rain events.
•More intense typhoons and hurricanes, with greater peak wind speeds and heavier precipitation.
Bruce Wielicki, climate expert at NASA Langley Research Center in Hampton, said the working group is trying to convey a better understanding of the big picture.
"Sea level in particular is going to be such a big issue" for Hampton Roads, Wielicki said. "It's really an issue for the whole community to try to deal with."
Wielicki had no role in this latest IPCC report, but did contribute a small section of writing and reviewed two chapters in the IPCC report issued last October that gave the physical science basis for climate change.
Hampton Roads is considered on the front lines of climate change because of its flood-prone, low-lying communities, the land's ongoing subsidence and the seasonal risk of hurricanes and storm surge.
Some local cities are beginning to assess their own risks, and last year Naval Station Norfolk was the subject of Department of Defense-funded computer simulations to study its vulnerability to major hurricanes and sea-level rise.
The IPCC report was written by 309 scientists from 70 countries drawing from about 12,000 scientific papers. Some 436 other authors contributed, along with 1,729 expert and government reviewers.
Dietrich can be reached by phone at 757-247-7892.