Flora and Fauna: The Essentials

27 Oct 2005 - Special Reports, Flora & Fauna, Arctic, Antarctic

Close-up of a Polar Bear

The Arctic and Southern Oceans may be comparable in the abundance and adaptation methods of the species they harbour in their waters, but the flora and fauna of the polar lands could not be more different. Whereas Antarctica is a continent on which the largest land based animal is a midge and the tallest plant is a variety of grass, the continental regions that lie north of the Arctic Circle are home to a host of mammals, shrubs and even small birch trees in the lower latitudes. Today, both regions lie at the forefront of the ravages brought on by global warming and the exploitation of marine living resources: two human induced trends that threaten entire ecosystems and the survival of the animals that rely on them.

Why don't polar bears eat penguins? A trick question that still generates a surprising number of wrong answers...

The short answer to the trick question is that polar bears and penguins can never meet because they live at opposite ends of the Earth! Read on to find out more about the extraordinary biological diversity in the contrasting polar regions.

Antarctic Fauna

Home to penguins, seals, whales, fish and birds, but no land based animals larger than a half centimetre long midge, the Antarctic is overwhelmingly associated with its marine environment. Indeed, whilst the Antarctic continent is the driest, coldest and most inhospitable region on Earth, the Southern Ocean teems with life and is one of the planet's most productive and complex marine ecosystems.

Krill: the very bottom of the food chain

Rich Waters

According to Dr Cynthia Tynan, of the University from the University of California at San Diego, this productivity and complexity of the Southern Ocean is due to a thick layer of warm, saline, nutrient-rich water which permeates the Antarctic Circumpolar Current (ACC) swirling round Antarctica. Although the waters of the Southern Ocean are the coldest in the world, they are still much warmer than the super-cooled Antarctic atmosphere and are filled with enough nutrients such as phosphate, nitrate and silicate to sustain the growth of phytoplankton necessary to breed an estimated 100 million tons of krill a year.

The massive krill presence, in turn, attracts bigger species that feed on them, including whales, pinniped species, such as crabeater seals, leopard seals, fur seals, and birds, such as petrels and penguins. It also sustains the native fish, squid, krill and other marine species, some of which have developed a special 'antifreeze' component to their body fluids enabling them to survive in waters as cool as -1.8°C.

Migrating to survive

Most of the Antarctic animals with fixed body temperatures between 35 and 40°C breed and feed in Antarctica during the warmer austral summer, but must migrate back north again during the fierce winter to find shelter from the increasing cold and darkness. While most of these winter in the Subantarctic with its nineteen islands and archipelago, some species of migratory whales and birds such as the Wilson's storm petrel, travel as far as the Northern hemisphere and the Arctic summer.

The only exception amongst fixed temperature animals is the emperor penguin which remains on the sea ice close to the Antarctic continent to breed and hatch its eggs during the winter and which survives by huddling together in groups.

Fauna in the Antarctic region which do not migrate, because their body temperatures are not fixed, include: a handful of tiny terrestrial invertebrates that live along the coastline; fish, squid, krill, copepods and other organisms living in the open waters; and sponges, soft corals, star fish, nemertean worms, crustaceans and other invertebrates which populate the bottom of the Southern Ocean.

A Delicate Balance

In recent decades, thanks to the richness of the Southern Ocean, whale and seal numbers have come back dramatically (although far from completely for whales) from their near extinction as a result of whaling and sealing activities in the 19th and 20th centuries. However, the delicate balance of the Southern Ocean and the species that live there has once again become a growing concern. This time it is because of new pressures such as pirate fishing of species like the Patagonian toothfish, and warming temperatures both of the Antarctic Peninsula region and the ocean itself due to human-induced climate change (link to existing climate change articles).

One such concern has been the reduction in pack ice and its negative effect on the development of juvenile krill, a key Southern Ocean species and the main food resource for various whales, seals, penguins, fish or squid. Already some species of penguins and seals have been dropping in numbers on the Antarctic Peninsula, as well as further north in South Georgia.

Antarctic Flora

Although Antarctica is 98% covered by ice and snow, its ice free regions, mostly to be found around the coastal areas, are nevertheless home to two species of flowering plants, three hundred and fifty species of lichens, one hundred species of mosses and hundreds of species of algae.

The greatest variety of Antarctic flora can be found on the north western side of the Antarctic Peninsula (the wettest, warmest and northernmost region of the Antarctic continent). Some species of lichen can also be found in the much more extreme environments of the Dry Valleys of Victoria Land, one of the coldest and driest ice free regions on Earth, as well as on southern nunataks (rocky outcrops that pierce through the Antarctic ice cap).

Lichens, rather than single plants, are a symbiotic association of fungi and algae cells cohabiting and growing extremely slowly, sometimes over many thousands of years. Other remarkable organisms are the endolithic algae (perhaps the hardiest on Earth) that can be found in cracks and pore spaces inside the sandstone and granite rocks where they are protected from the violent and extremely cold katabatic winds that blow down from the Antarctic Plateau.

Living Barometer

Recently, scientists have also regarded Antarctic flora as a kin of "global warming barometer". They do this by studying how rising temperatures along the Peninsula region have enabled mosses, lichens and in particular Antarctica's two flowering plants to grow further and further south as they benefit from increasing periods of thaw.

Arctic Fox

Arctic Fauna

Although the great white bear, or polar bear, is arguably the best known of all Arctic animals for its splendid appearance and ability to live and hunt both on land and at sea (either swimming or traveling across pack ice), the Arctic region is in fact home to a wide variety of land and marine species.

On land, species include mammals such as the larger reindeer, moose, caribou and musk oxen, but also smaller Arctic foxes, wolves, hares, ermines, lemmings and ground squirrels. In the Arctic Ocean, they include mammals such as bowhead whales, belugas, narwhals, orcas, sea otters, seals and walruses, as well as various fish and a whole range of marine invertebrates such as sponges, jelly fish, sea anemones, urchins, clams, squid or sea spiders.

The Arctic is also home to a large variety of birds, including fulmars, skuas, ivory gulls or guillemots to name a few, and serves as a breeding ground to long distance migratory birds, including hundreds of thousands of geese, ducks and waders.

Other native Arctic animals are the swarms of insects which live in the tundra regions and include flies, moths, grasshoppers, black flies, Arctic bumblebees and above all mosquitoes which make life very uncomfortable for other animals and humans during the summer months.

Resilience and Adaptability

Although these Arctic animals are distributed unevenly across the Arctic region with some species native to northern Canada and others to the northern part of the Eurasian continent, what they have in common is an incredible resilience and capacity for adaptation to their harsh environment.

This enables them to survive the massive fluctuations in temperature, environment, daylight and resources between the summer and the winter months. For Arctic mammals, methods of adaptation can include: the fur seal's thick oily fur coat; the walrus' thick layer of fat which serves as insulation, the snow hare's large paws that act like snowshoes; and the polar bear's ability to hibernate and go without foods for up to three months in the winter.

For most birds, adaptation and surviving the winter months usually implies migrating south to warmer latitudes (except for the snowy owl and a very few other species that remain in the Arctic regions throughout the year).

The methods of adaptation of marine animals tend to resemble those of marine life in the Southern Ocean. Marine mammals such as whales and seals have developed a thick layer of blubber that serves as insulation, while various fish, as in the Antarctic, have developed antifreeze proteins to survive the sub-zero water temperature.

Similarly, beetles, moths and other Arctic insects concentrate various molecules like glycerol in their body in order to allow tolerance for ice formation within their body fluids (freeze tolerance). An alternative strategy allowing terrestrial invertebrates to survive under the snow during the winter is to avoid ice formation within the body cavity (freeze avoidance).

Transformation of Ecosystems

As was highlighted by the recent publication of the Arctic Climate Impact Assessment (ACIA) report (LINK TO ACIA SITE), recent decades have seen a generalized trend towards Arctic warming, with temperatures in some regions rising by as much as 3?C in the last fifty years - more than ten times faster than the rest of the planet. This has brought with it a rapid transformation of Arctic ecosystems, most notably the retreat of summer sea ice and the melting of the permafrost. Such changes are causing increasing problems for species associated with sea ice, whether they are single-cell algae, the copepod crustaceans which graze on them, the fish which hide in the ice cracks, etc. If these trends continue, polar bears in particular are unlikely to survive as a species as they are dependant on sea ice to hunt seals and use ice corridors to move from one area to another.

Other species which are being increasingly affected by the warming of the Arctic include: ice-dependent seals that give birth to and nurse their pups on the ice and use it as a breeding platform; migratory birds, which are seeing a rapid decrease of tundra nesting areas as the tree line advances northward; and reindeer which depend on abundant (but declining) tundra vegetation and foraging conditions. On the increase, however, are insect outbreaks, in particular of mosquitoes, but also of spruce beetles which feed on and destroy spruce forests.

Arctic Flora

According to its most common definition, Arctic flora encompasses those plants found north of the tree line in the tundra regions. Much more varied and prolific than Antarctic flora, Arctic flora includes thousands of different species of mosses, lichens, flowering plants and berries, as well as small trees such as the larger arctic dwarf birch and pussy willows. The number and proliferation of Arctic plant species varies from region to region, but the greatest variety can be found in Northern Europe, along the Arctic Circle from northern Russia to northern Scandinavia and Spitzbergen.

Adaptation

Arctic plants have also adapted to rapid fluctuations in temperature and to long winters where temperatures can dip as low as -30°C. Arctic plants can survive on what are usually very thin layers of acidic and nitrogen poor soils covering either bedrock or permafrost, and can freeze one minute and thaw the next so as to make the most of the brief spells of sunshine and warmer weather in July and August.

Arctic flowering plants include dandelions, buttercups, harebells and chamoville daisies. The tundra meadows are home to purple saxifrage, yellow cinquefoils, Lapland rosebay, white bells and mountain averns. Lichens can be found on rocky ground and outcrops and crowberries, blueberries, cranberries and alpine bearberries are all part of the Inuit and other Arctic people's diet. Other notable plants found in the Arctic include wintergreen, moss campions, arctic cotton, louseworts, the prolific fireweed, prickly saxifrages, bladder campions and mouse-ear chickweed.

Melting Permafrost

Along with Arctic animals, Arctic plants are first in line to feel the effects of climate change and warming temperatures. Whilst the warming of the Arctic region will, in the medium to long term, mean the extension of the tree line towards the North, this is at the expense of permafrost that has already begun to melt, and of its native flora. Already, hundreds of pools and lakes and the flora that inhabit them are in the process of disappearing as water drains into the thawed soil.

By: Jean de Pomereu