Habitat loss

Publication - April 1, 2008
The climate is changing faster than at almost any time in our planet's history. Without a dramatic cut in greenhouse gas emissions, the die out in species could be astonishingly severe.

A recent major study says a global temperatures increase of 1.8–2° Celsius (3.2-3.6°F), considered a mid-range estimate, threatens a million species with extinction over the next 50 years. Only rapid reductions in emissions in the next few decades can avoid this loss. Many species can still be saved, but it is fast running out. If temperatures go even higher, more species will be lost.

"Most of the world's endangered species -- some 25 percent of mammals and 12 percent of birds -- may become extinct over the next few decades as warmer conditions alter the forests, wetlands, and rangelands they depend on, and human development blocks them from migrating elsewhere." -- UN Framework Convention on Climate Change.

 

Many ecosystems are already stressed by human activities – destructive logging, excessive grazing, over fishing, toxic pollution and more. And, human development and habitat destruction impedes many species from migrating – superhighways effectively block land animals, for example.

Many ecosystems are already stressed by human activities – destructive logging, excessive grazing, over fishing, toxic pollution and more. And, human development and habitat destruction impedes many species from migrating – superhighways effectively block land animals, for example.

Some examples of species and habitats at risk:

Coral reefs

Coral bleaching is a condition that can seriously damage and kill entire coral reefs. Corals contain microscopic algae called zooxanthellae that provide the coral with food and give them their vibrant colours. Rising ocean temperatures cause corals to become stressed, and they expel the zooxanthellae and turn white or "bleach". If zooxanthellae do not return to the coral’s tissue, the coral will die.

As little as a 1° Celsius (1.8°F) increase in temperature above the summer maximum can cause corals to bleach. Tropical sea temperatures have increased by 1° Celsius over the past 100 years and are predicted to continue rising.

In 2002, Australia’s Great Barrier Reef experienced its worst case of coral bleaching. More than 60 per cent of the 2,000-kilometer reef was affected. If the projected rate of climate change isn’t slowed, the reef will be dead in decade. Hundreds of species that rely on the reef will also die out.

Polar bears

Polar bears in Churchill in Manitoba, Canada have to be tranquillised then airlifted north in order to access their natural habitat as the sea ice is returning later and later after the summer months.

Arctic sea ice could disappear within 70 years, and wild polar bears with it.

Polar bears are the world's largest land predator. They can go for long periods, even months, without eating, but need to build up fat to live through lean times. The polar bear does this mostly by eating seals caught on sea ice. Without the ice they can't get to their prey.

In fact, without sea ice, much of the Arctic ecosystem would change or collapse. Polar bears also use floating sea ice platforms for travel. Pregnant polar bears build snow dens for the winter, which they give birth in.

In the last two decades, Arctic sea ice cover has retreated five percent and the ice that is left has lost at least 30 percent of its thickness; and an average of two weeks have been lost from the polar bear's hunting season.

Plants

Like animals and insects, plant species require specific climates. Yellow birch trees don’t grow next to Saguaro Cactus, for example.

Changes in precipitation and temperature will mean that some species can no longer survive where they now grow. Also, like animals, plants are vulnerable to competition. As warming occurs, species adapted to cooler climates can be pushed out of existence by newcomers better suited to the new temperatures.

Most plants can't migrate very quickly, compared to animals and insects, because of the slow travel of seeds and pollen. The climate will change too fast for many of them if current trends continue. Human barriers (such as farms and urban areas) will also impede plant migrations.

Many animals and insects need specific plants, or types of plants, as part of their habitat.

So the loss of plant species will have a ripple effect – leading to more animal and plant extinctions.

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