During the record heat waves of the summers of 2004 and 2005, more than 10 million acres of forest burned. Off the coast, a swath of sea ice the size of Texas disappeared. Newspapers ran reports of drowning polar bears, native villages falling into the water, and declining salmon runs.
That night, we camp on a steep meadow blanketed with wispy white dryas, next to a gnarled alder that’s just leafing out. This campsite would have been covered by glacial ice a few dozen years ago. But the glaciers of southern Alaska and neighboring Canada are particularly sensitive to 20th-century warming; in fact, some have thinned more than 2,000 feet in 52 years. Although these glaciers comprise less than one percent of the earth’s glaciated area, scientists estimate that they are responsible for nearly half of the past decade’s worldwide sea-level rise attributable to melting ice.
Thirty-six lines of latitude south of the Kennicott Glacier, I reach over the side of my canoe and dip a finger into a tea-colored creek in Everglades National Park. Here, at the headwaters of Hells Bay, the water should run fresh in the final hours of an outgoing tide. But my portable salinity tester (my tongue) confirms that I am floating on very salty water.
Until recently, the eastern reaches of Hells Bay–a seemingly infinite series of ponds, islands, and narrow creeks at the headwaters of an immense mangrove swamp–were a transition zone. Here, the fresh water (that comes from rain falling inland) wages a subtle battle with the tides, pushing salt water out of the interior and creating one of the most productive wetlands on earth. This once was a perfect habitat for wading birds, freshwater fish, alligators, and many other species that took refuge here as development ate away at South Florida’s natural environments.
Unfortunately, over the past 130 years, the Everglades have been degraded by a series of water management projects that were conceived with good intentions, but without much understanding of ecosystems. Built by the Army Corps of Engineers, an extensive system of canals and levees opened the valves on development and agricultural growth, and isolated the park from much of the life-giving sheets of fresh water coming down from the north. The water that does arrive often comes at the wrong time, flooding nests of birds and reptiles, and it’s often polluted with high levels of nitrates and phosphates. Many mammals have left, and nesting birds have declined by 90 percent. Everglades is now home to 14 endangered species, more than any other national park.