LUDINGTON, MICH. – As the wind whipped across the top of the Big Sable Point lighthouse, one of the most famous and beloved on the Great Lakes, Jim Gallie pointed to the disappearing beach: "It's been progressively getting worse."

Hikers and beachcombers who trekked along the shoreline to the remote, historic lighthouse at Ludington State Park once had ample room between the waves and the metal breakwall.

Now the Michigan Department of Natural Resources is spending $130,000 to recap the sea wall and place new stone barriers at its base. "If it wasn't for that sea wall," said Gallie, the park manager, "those dunes would be gone."

From 112 feet above the beach on the deck of the 1867 lighthouse, the effects of a changing climate and a lake near historically high levels are clear: Increased precipitation, rising temperatures and human development across the Great Lakes basin have changed Lake Michigan and the lives of the millions who live, work and play along the coast in Michigan, Indiana, Illinois and Wisconsin.

"It's a system that's really been whipsawed in many ways by a variety of factors, from climate change to nonnative species, to the legacy of contaminants," said J. Val Klump, dean and professor at the School of Freshwater Sciences at the University of Wisconsin at Milwaukee.

As part of the series "Great Lakes, High Stakes," the Chicago Tribune is exploring the environmental issues and how coastal communities are adapting to a warming world.

The third largest Great Lake by surface area (second by volume) is an eclectic mix of dune bluffs, sandy beaches, rugged rocks, major Midwestern cities, tourist towns and marshlands. But it is also emblematic of the myriad issues facing all of the Great Lakes as the climate continues to change. Surging water levels have collapsed bluffs, swamped coastal dune lands, erased beaches and damaged homes, businesses, docks, trails, campgrounds and sewer systems.

Residents and officials are scrambling to find new solutions as stone barriers and beach replenishment are often too costly and ineffective over the long term. In Illinois, environmental officials, engineers and scientists are experimenting with offshore reefs and shoals with the idea of blunting the force of storm surges before they eat away at the sand, dunes and marshland habitats.

In Wisconsin, cities and towns up and down the coast are spending millions on projects such as stormwater sewer upgrades and pier stabilization. In Indiana, shoreline protection has been contentious, including a federal lawsuit filed by residents and officials of Ogden Dunes who claim dunes, roads and private homes are "in danger of total destruction" if current protections fail.

On the western shores of Michigan, houses have begun to slip into the lake, leading homeowners to stabilize their structures, build waterfront barriers or move altogether.

In Orchard Beach State Park, north of Manistee, Mich., park officials are planning to relocate the historic pavilion building that overlooks the lake because of the danger of erosion.

Doug Barry, unit supervisor at the park, described moving the entire structure, a 400-ton limestone building with a concrete foundation, as "controlled retreat." "It's a temporary fix," he said. "Lake Michigan is going to win."

The movement of sand, and its effects on the shoreline and the underwater environment, is the focus of offshore projects at Illinois Beach State Park in Zion and the Fort Sheridan Forest Preserve in Lake County, north of Chicago.

There, a consortium of agencies, including the U.S. Army Corps of Engineers, the Illinois Department of Natural Resources, private researchers and the Lake County Forest Preserves, is working to install a series of offshore reefs and underwater natural breakwalls. The goal is to protect the shoreline, but also study whether reducing the flow of sand, sediment and crashing waves along the shore will alter the character of the lake itself, the nearshore habitat, the beaches and the unique marshlands beyond.

Scientists across the Midwest are studying how changes in air and water temperature are altering the water, aquatic life and the proliferation of invasive species. University of Minnesota researchers Tedy Ozersky and Sergei Katsev have been studying the effect of the quagga mussels on the biology and chemistry of the lake.

What they have found is that the quagga mussels, an aquatic mollusk native to Ukraine that arrived in ballast water from transoceanic vessels in the early 1990s, have outcompeted zebra mussels in the deep regions of the lake bottom. Their impact stretches beyond changing the food web. Their proliferation has filtered the water and changed the chemistry of the sediment. When the researchers lowered a camera into the water, they were surprised at not just how many mussels they saw, but also how active they were. "It looked like they were having a party," Ozersky said.

The invasives, he said, can filter 200 meters of lake in a matter of days, pulling the nutrients from the water, stealing them from other creatures that need them to survive.