Keystone species' loss could cause ecosystem to collapse

Although many species will thrive with warming temperatures, some may not and an imbalance could have catastrophic results in the ecosystem.

There are certain animals worldwide that hold a heavier sway in the balance of ecosystems, and they were dubbed "keystone species" in 1969 by American zoology professor Robert T. Paine.

The theory is that like the wedge-shaped keystone (or headstone) that locks together all the pieces used in an architectural arch, there are species that keep certain ecosystems in together. Removal of the species can cause the eventual collapse of the ecosystem.

Just a drop in the bucket of the keystone species affected by global warming are reviewed below.

POLAR BEAR AND WALRUS

The polar bear, long the most-often touted of threatened species, indeed is in trouble with reduction of ice pack in the Arctic. As the apex predator, the bears keep their food source population — mainly seals, but also walruses and whales — in balance.

What is not commonly known is that polar bears also are good scavengers in scarcity and will move into other animals' food source if necessary. Polar bears will happily consume fish, reindeer, birds, rodents, eggs, kelp, berries and trash left by humans — putting them in competition with arctic foxes and seagulls, instead of providing a symbiotic relationship by leaving leftover prey.

Photo gallery: Animals that will thrive under global warming

The walrus is also a keystone species that is threatened in the Arctic and elsewhere. Walruses prefer to dine on mollusks such as clams, but also eat shrimp, crabs, soft corals, sea cucumbers, tube worms and the occasional seal, so the decline of walruses allows many of their prey to bloom into overpopulation.

Since they rely on the ice pack for their reproductive periods, the reduction of ice separates lactating cows for longer distances from their calves in order to get to the best feeding grounds.

AFRICAN ELEPHANT AND PRAIRIE DOG

As wrinkly as a walrus, and also equipped with tusks, is the African elephant. The savannah is a warm place, destined to get warmer, and already drought and flooding have wreaked damage across the plains.

With a requirement of 300-600 pounds of food a day, the African herbivore is dependent on robust plant life and plenty of water from its ecosystem, according to National Geographic. They, in turn, keep acacia populations in check, so that the savannah remains a grassland.

The grasses are key for grazing species such as zebra and antelope, and burrowing animals such as mice and shrews. Although the elephant isn't a predator, it maintains the ecosystem of the savannah so that the key predators (themselves keystone species), lions and hyenas, have plenty of food to survive.

Another animal that provides key environmental balance for other species is the prairie dog.  According to the Defenders of Wildlife website, the animals support the life cycles of 150 other species.

While some animals such as tiger salamanders, snakes, burrowing owls and critically endangered black-footed ferrets reuse prairie dog burrows as homes, others, like eagles, coyotes and badgers feed on them. Even prairie plant species rely on them for fertilization and aeration of the soil.

It is suspected that a warmer climate is changing the foraging behaviors of the prairie dogs, according to a study by the University of Colorado and Kansas State University. More sustained foraging of their habitat could be devastating to the grasslands.

PACIFIC SALMON AND SEA OTTER

Pacific salmon, especially sockeye, are dependent on certain temperatures for optimizing their metabolism. Warmer waters reduce crucial oxygen levels in the streams and rivers where they breed. With higher water temps, they require more food such as aquatic insects and small fish, and for sockeyes, plankton.

When food sources are not readily available, massive die-offs happen, like in Western Alaskan species in 1997-1998, according to the U.S. Fish & Wildlife Service. Animals that rely on the salmon for food are then left hanging — otters, eagles, bears and humans.

Sea otters, the cuddly postcard species from the Pacific Northwest, are important predators for the sea urchin population, according to National Geographic. If allowed to breed indiscriminately, sea urchins will decimate kelp forests, which are both food and home to multiple species in the area, including crabs, snails, geese and fish.

A disquieting prospect it is, realizing the impact of global warming on keystone species and the planet at large. Even the winners in global warming can come out losers — some species adapt quickly to the warming trends, but their environment and food sources don't always keep pace. So, after a brief surge in population, a steep decline often follows because of starvation and lack of resources.

A cautionary tale indeed for the keystone species who are able to read and understand the implications.

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