There aren't very many places in the world where you can walk around and witness first-hand how a landscape is recolonized by flora and fauna after centuries of being covered in ice. One of these rare places is Glacier Bay National Park in southeast Alaska.

Starting somewhere around 1300 AD, the planet experienced a period of cooling that, while not a true ice age, was dubbed the Little Ice Age. While the exact start of the Little Ice Age is debated, what is certain is that during the centuries of particularly cold winters, glacial activity rose, with glaciers forming and advancing in areas all over the globe. Pack ice pushed forward from the Arctic, and glaciers poured down through mountain ranges in large swaths of Europe and North America, including what is now known as southeast Alaska.

Small chunks of ice from icebergs line the rocky shore near a glacier in Glacier Bay National Park. Small chunks of ice from icebergs line the rocky shore near a glacier in Glacier Bay National Park. (Photo: Jaymi Heimbuch)

This cooling peaked around 1750 and ended in the middle of the 19th century. In the time since, Glacier Bay National Park has seen dozens of glaciers advance and retreat, with an emphasis on retreating. Because of the density of glaciers, this special place is still one in which visitors can see how a landscape goes from being scraped down to bare rock by centuries of sliding ice to being recolonized by plants and animals and, importantly, how that recolonization happens.

Coastal landscape of Glacier Bay National Park. Coastal landscape of Glacier Bay National Park. (Photo: Jaymi Heimbuch)

Glacier Bay National Park has long been a source of first-hand information about how glaciers impact ecosystems. Indeed, it is where John Muir traveled to find proof for his controversial theory that a glacier formed Yosemite Valley.

"John Muir came here in 1879 pursuing the reality of what he had earlier tracked as a mere ghost throughout California's High Sierra," reports the Official National Park Handbook of Glacier Bay. "In Glacier Bay country, just below the shoulder of Alaska's south-reaching coastal arm, Muir trekked the real thing in action. He contemplated landscapes newly emerged from the Little Ice Age... Muir knew: At Glacier Bay you can get lost both in space and in time."

This is still true today. Though some glaciers have melted away completely and others have retreated miles inland, there are still a number of tidewater glaciers that calve into the sea with spectacular booms and splashes. And there remains the ability to wander up the side of a glacier or a recently revealed smooth-rock cliff and watch the next phase of life taking hold.

The landscape moves from lichens and mosses, to grasses and wildflowers, to alder and willow, and finally spruces and hemlocks.

As the glaciers melt away, the exposed rock is recolonized by lichens and mosses. These cover the rock and break down to build the first hints of soil, as well as provide food for animals. Next, dryas finds a footing in the rock and spreads into a carpet of vegetation, inviting wildflowers and grasses to take root as well. These plants provide more food for more varieties of plant and animal life that eventually return, including insects, shrews and voles, mice and bats all which attract more and more predators and competitors.

Eventually, and with the assistance of seed-dispersing birds and animals such as mountain goats, alder and willow plants take hold.

"Within several decades, alders form dense, nearly impenetrable thickets, growing so tall and ropy that they cannot hold themselves upright any longer," writes Karen Jettmar in Alaska's Glacier Bay: A Traveler's Guide. "Cottonwoods move in, cutting off sunlight to the alders and willows, their leaves adding to the growing layer of topsoil."

Finally, with the decades of decaying plant matter and activity creating a thick layer of soil, forests of spruce and hemlock rise up and become the green conifer forests we expect to see when we think of southeast Alaska.

Conifer forests are established within a few decades of ice retreating. Conifer forests are established within a few decades of ice retreating. (Photo: Jaymi Heimbuch)

As the spruce forests age, their needles add to the acidity of the soil and eventually they kill themselves off, since they cannot tolerate acidic soil. The stands of spruce give way to hemlock, which can thrive for centuries.

Another result of the acidification of the soil by spruce needles — as well as the spread of moisture-retaining sphagnum moss — is the creation of muskeg. This is a boggy habitat dominated by thick mats of spongy, springy sphagnum moss, carnivorous sundew plants, thickets of blueberry and other low-growing plants that enjoy the wet, acidic environment.

Muskeg, while found much more abundantly in the temperate rainforest south of the park, is just starting to form in Glacier Bay since it takes a good deal of time to form. Eventually, more will be found in this area still emerging from the ice.

"Muskeg represents a wondrous coming full circle, a return to openness though not to barrenness," writes the Official National Park Handbook of Glacier Bay.

As spruce forests age and die off, the acidic soil is covered in sphagnum moss and other species that thrive in muskeg. As spruce forests age and die off, the acidic soil is covered in sphagnum moss and other species that thrive in muskeg. (Photo: Jaymi Heimbuch)

All the different stages of this process of moving from ice to bare rock to forest can be seen within the park, as well as an abundance of wildlife species.

"The wonder of plant succession in Glacier Bay," writes Jettmar, "is that you can watch the world being created without human interference. Here, you can witness the process that healed North America and Europe after ice age glaciers retreated more than 10,000 years ago."

If you wish to be lost in time and the fascinating and tenacious transitions of life and species, a visit to this special national park will do the trick.

Glacier Bay National Park shows the persistent adaptability and tenacity of flora and fauna. Glacier Bay National Park shows the persistent adaptability and tenacity of flora and fauna. (Photo: Jaymi Heimbuch)

Jaymi Heimbuch ( @jaymiheimbuch ) focuses on wildlife conservation and animal news from her home base in San Francisco.