Natural Noah's Arks on Earth

Many animals and plants hold on to existence in fragments of their former homelands, surrounded by a flood of human farms and homes.

Like Noah's Ark, certain regions of the Earth preserve remnants of lost worlds. A flood of human settlement washes away some natural environments, leaving only fragments. These biological Arks provide endangered wildlife with a final toehold before extinction.

New Zealand Provides a Sanctuary

Fences, gates and other defenses protect a 1-square-mile valley located 10 minutes from downtown Wellington, New Zealand. The sanctuary, Zealandia, provides a fortified home for some of Earth's rarest and oddest creatures. Nearly 40 species of native birds live in the sanctuary, including iconic yet endangered kiwis and the takahē, a flightless bird once though extinct.

The tuatara also resides in Zealandia. Tuatara resemble lizards, but actually represent the last two species from a reptile group known as rhynchocephalians. Biologists consider the tuatara living fossils because the animals preserve primitive characteristics, such as simple single-chambered lungs. In 2005, conservation managers released tuatara into Zealandia, marking the return of the reptiles to the main islands after a 200-year absence. The tuatara had been eradicated from the main islands by European settlers along with non-native cats, rats, dogs and other predators.

Thousands of square miles of grassland once blanketed the Great Plains of North America from southern Canada to central Texas and from Indiana to Montana. European settlers called the prairies, "the Sea of Grass." Now, only a few isolated patches of tallgrass and shortgrass prairies remain in an ocean of farms and cattle pastures. Enormous herds of bison once stopped forests from invading the prairies as the animals devoured tree saplings. This role made the bison a keystone species of the prairie, meaning the ecosystem depended on their presence. Now, the bison have been killed off in most of the United States.

In eastern Kansas and Oklahoma, chunks of limestone and chert in the prairie soil frustrated farmers. The wave of Europeans swept west and left the region, known as the Flint Hills, with the largest remaining tract of tallgrass prairie in North America. The largest protected area in the Flint Hills, the Tallgrass Prairie Preserve, protects 45,000 acres complete with bison. The Flint Hills National Wildlife Refuge preserves another 18,463 acres.

The Amazon rainforest receives the world's attention, concern and love, but another South American ecosystem faces an even graver threat. The Atlantic Forest once covered approximately 330 million acres of the South American coast from the eastern point of Brazil to northern Argentina. As Portuguese settlers forged Brazil, they left only about 7.8 percent of the forest, according to a study in Biotropica. Isolated fragments make up much of that remaining forest. Yet it remains home to the one of widest varieties of plants and animals on the planet.

The fragmented patches of the Atlantic Forest still shelter approximately 2,200 animal species, not counting invertebrates, according to the Nature Conservancy. Twenty one species of monkey live only in the Atlantic Forest, including the golden lion tamarin. The monkeys have trouble crossing farms, roads and towns to reach other forest fragments. The isolated animals face inbreeding and extinctions. Conservation managers work to create corridors between these patches to allow the animals to mingle and access more food and shelter.

Today, forests cover approximately one-third of Germany, roughly the same amount as in the 13th century, according to a report by the German Federal Agency for Nature Conservation. Most of those forests regrew after extensive deforestation from the 13th to 18th centuries. However, in the Black Forest, one small section of ancient German forest survived untouched. A land survey from 1787, recorded that only 667 acres remained of the old growth forest, which contained 600-year-old oak trees and 250-year-old beech trees, according to the book "Grazing Ecology and Forest History." That fragment, known as the Unterholzer Wald, was preserved as a park to protect deer stocks.

The raised bogs of northwestern and sub-Alpine Germany harbor specially adapted plants, including the insect-eating sundew and peat mosses. The bogs formed after lakes and ponds filled in with soil, but many were drained and plundered for their peat deposits in the 18th and 19th centuries. The International Union for the Conservation of Nature named the German raised bogs as a critically endangered ecosystem in 2013. Although bog soils release few nutrients when waterlogged, drained bogs become fertile fields for crops. Remnants of the bogs survive, but their distance from each other stops plants and animals from moving between them.

The International Union for the Conservation of Nature lists the Cape Flats Sand Fynbos as another critically endangered ecosystem. Fynbos are shrublands found only in the Western Cape of South Africa. Fynbos contain many rare, endemic plant species, meaning the plants live there and nowhere else. The Cape Flats Sand Fynbos shelters the rarest of the rare plants and the greatest biodiversity of all the fynbos, although the ecosystem has been swallowed by Cape Town.

The Cape Flats Sand Fynbos covers only a tiny area, almost entirely within the city limits of Cape Town. As the city grows past 4 million residents, pressure builds on the fynbos. Biologists believe at least eight species of endemic plant have already gone extinct as the city sprawled. Botanists struggle to save others, like the Cape Flats Cone Bush (Leucadendron levisanus).

The Madrean Sky Islands soar above the Sonoran and Chihuahuan deserts along the U.S.-Mexico border. The "islands" are actually mountain peaks. The harsh desert isolated the peaks from each other after the Ice Ages. Pine and oak woodlands cover these peaks and provide shelter for species found no where else, such as the Mount Graham red squirrel and Jemez Mountains salamander. However, climate change threatens to bring the dryness of the desert to the sky islands. As temperatures rise, the woodlands retreat up the mountainsides, but there is only so far they can go.