On satellite imagery, the Lena River Delta on the northern coast of Siberia gives the appearance of a fan coral, its braided channels and numerous lakes forming an intricate pattern across the Arctic tundra. It is this landscape of countless pools and waterways that attracts huge congregations of loons, grebes, shorebirds and waterfowl to this 11,600 square mile wetland to nest and raise their young during the brief Arctic summer.
The Lena River, the second largest stream in Siberia, rises a few miles west of Lake Baikal, flowing northward and gradually eastward for 2700 miles to its delta on the Laptev Sea. There it delivers tons of sediment each year, gradually enlarging and enriching the delta which is also an important spawining area for Arctic fish. Nesting birds of note include red-necked grebes, four species of loon, whooper and tundra swans, bean geese, black brant, king and Steller's eiders, long-tailed ducks, Ross's and Sabine's gulls and numerous shorebird species. Of course, willow grouse, rock ptarmigan, snowy owls, peregrine falcons and a wide variety of Arctic songbirds also inhabit the delta. Resident mammals include gray wolves, Arctic fox, wolverines, least weasels, stoats, lemmings, tundra voles and reindeer; beluga whales, walruses and a variety of seals often visit the area.
Fortunately, most of this vast tundra wetland is protected within the Lena River Delta Nature Reserve, the largest nature preserve in Russia. Visited only by the most adventurous naturalists, this spectacular but remote site is relatively free of human disturbance; nevertheless, the Lena, like all rivers on our planet, is tainted by pollutants from agriculture, mining, industry and sewage and their long term effects on the delta ecosystem is yet to be determined.
Tampilkan postingan dengan label Arctic. Tampilkan semua postingan
Tampilkan postingan dengan label Arctic. Tampilkan semua postingan
Senin, 25 Juni 2012
Senin, 28 Mei 2012
The Arctic Fox
Mention Arctic land mammals and the image of large, well-insulated creatures comes to mind: polar bears, musk ox, caribou and the extinct woolly mammoth, to name a few. But the small Arctic fox, the most northern-living canine on our planet, has managed to thrive on the harsh, treeless tundra of the Arctic biome. Equipped with a compact body habitus, thick, dense fur, furred paws and changing coloration to blend with its environment, this hardy fox also has an exquisite sense of hearing for prey location, adapts well to an omniverous diet and produces large litters to sustain its population.
After breeding in late winter or early spring, the monogamous pair uses a large den network in which to raise its litter of 6 to 15 or more kits; the newborn fox will remain with their mother through the summer and, as with some other wild canines, a few yearlings often stay behind to assist with feeding and protecting their younger siblings. The diet of the Arctic fox is dominated by lemmings and other small mammals (including seal pups) but also includes berries, vegetation, carrion, birds, fish and the eggs of seabirds and waterfowl. When food is abundant, they will bury eggs or meat in the Arctic permafrost for consumption during the harsh months of winter.
Circumpolar in their distribution, the populations of Arctic fox are stable in most areas though they are endangered in Scandinavia due to overhunting. Having evolved late in the Pleistocene, about 250,000 years ago, they spread across northern oceans on the vast ice shelves of that Period and are the only mammal native to Iceland. Today, like many polar species, Arctic fox are threatened by global warming that is changing their habitat, altering their food supply and allowing dominant predators (such as red fox and gray wolves) to invade their territory.
After breeding in late winter or early spring, the monogamous pair uses a large den network in which to raise its litter of 6 to 15 or more kits; the newborn fox will remain with their mother through the summer and, as with some other wild canines, a few yearlings often stay behind to assist with feeding and protecting their younger siblings. The diet of the Arctic fox is dominated by lemmings and other small mammals (including seal pups) but also includes berries, vegetation, carrion, birds, fish and the eggs of seabirds and waterfowl. When food is abundant, they will bury eggs or meat in the Arctic permafrost for consumption during the harsh months of winter.
Circumpolar in their distribution, the populations of Arctic fox are stable in most areas though they are endangered in Scandinavia due to overhunting. Having evolved late in the Pleistocene, about 250,000 years ago, they spread across northern oceans on the vast ice shelves of that Period and are the only mammal native to Iceland. Today, like many polar species, Arctic fox are threatened by global warming that is changing their habitat, altering their food supply and allowing dominant predators (such as red fox and gray wolves) to invade their territory.
Selasa, 08 Mei 2012
The Mackenzie River
Rising at the west end of Great Slave Lake in Canada's Northwest Territories, the Mackenzie River flows northwestward for almost 1100 miles to the Beaufort Sea. Un-dammed and winding through Subarctic and Arctic wilderness, its wide, braided channel is just the final conduit of a massive watershed that covers 20% of Canada, extending from northeast British Columbia, northern Alberta, northwest Saskatchewan and the western Yukon to the massive Mackenzie River Delta, the 12th largest on our planet. If one includes its most distant tributaries, this river system exceeds 2600 miles in length (the longest in Canada) and drains a watershed of almost 700,000 square miles.
To the southwest, the Peace and Athabaska Rivers rise on the east side of the Continental Divide in the northern Canadian Rockies; these large streams merge to form a large inland delta along Lake Athabaska, which drains to Great Slave Lake via the Slave River. Leaving Great Slave Lake, the Mackenzie River picks up meltwaters from the Mackenzie Mountains (to its west) via the Liard River system and then receives flow from Great Bear Lake, to its east, the largest lake in Canada. At its braided delta, just east of the Richardson Mountains, the Mackenzie discharges copious amounts of relatively warm, fresh, nutrient-rich water into the Arctic Ocean; this annual discharge, the 14th largest on Earth, dramatically affects the regional ecosystem, allowing boreal woodlands to extend well north of their usual range and increasing the diversity of plants and animals across the ever-changing delta. Beluga whales gather here in spring to molt in the mild river current and the countless, shallow lakes provide ideal breeding habitat for shorebirds, tundra swans and snow geese. Resident mammals include black bears, barren ground grizzlies, Arctic fox, Arctic wolves, caribou, moose, musk ox and a massive number of muskrats.
However, all is not well in this seemingly pristine wilderness. Dams on tributaries of the Mackenzie have reduced flow through its primary channel and are diminishing the annual floods that are crucial to the welfare of its delta ecosystem. In addition, worrisome levels of mercury have been found in the river over the past few years, the product of mining and power plant effluent across the watershed. Of course, as with other Arctic ecosystems, global warming may dramatically affect the natural diversity of this magnificent yet fragile landscape.
To the southwest, the Peace and Athabaska Rivers rise on the east side of the Continental Divide in the northern Canadian Rockies; these large streams merge to form a large inland delta along Lake Athabaska, which drains to Great Slave Lake via the Slave River. Leaving Great Slave Lake, the Mackenzie River picks up meltwaters from the Mackenzie Mountains (to its west) via the Liard River system and then receives flow from Great Bear Lake, to its east, the largest lake in Canada. At its braided delta, just east of the Richardson Mountains, the Mackenzie discharges copious amounts of relatively warm, fresh, nutrient-rich water into the Arctic Ocean; this annual discharge, the 14th largest on Earth, dramatically affects the regional ecosystem, allowing boreal woodlands to extend well north of their usual range and increasing the diversity of plants and animals across the ever-changing delta. Beluga whales gather here in spring to molt in the mild river current and the countless, shallow lakes provide ideal breeding habitat for shorebirds, tundra swans and snow geese. Resident mammals include black bears, barren ground grizzlies, Arctic fox, Arctic wolves, caribou, moose, musk ox and a massive number of muskrats.
However, all is not well in this seemingly pristine wilderness. Dams on tributaries of the Mackenzie have reduced flow through its primary channel and are diminishing the annual floods that are crucial to the welfare of its delta ecosystem. In addition, worrisome levels of mercury have been found in the river over the past few years, the product of mining and power plant effluent across the watershed. Of course, as with other Arctic ecosystems, global warming may dramatically affect the natural diversity of this magnificent yet fragile landscape.
Rabu, 28 Maret 2012
The Porcupine Caribou
Named for the Yukon River tributary that drains most of their range, the Porcupine Caribou Herd inhabits northeastern Alaska and the northern Yukon Territory of Canada. According to the last official count, in the summer of 2010, the herd is now composed of about 169,000 individuals, making this one of the most spectacular concentrations of migrant mammals on our planet.
After wintering in mountainous regions south and east of the Brooks Range, the Porcupine Caribou begin their spring migration in March, led by cows and yearlings (bulls and juveniles follow a few weeks later). Using three primary routes across the Brooks Range of Alaska and British Mountains of the northern Yukon, pregnant cows reach the North Slope by late May and calving begins, synchronized to reduce the impact of predation by wolves, grizzlies and golden eagles; the formation of nursery groups and the rapid development of calves (able to run within 24 hours) also serve to diminish loss of the newborns. As the bulls and juveniles arrive, the caribou assemble in huge herds, feeding on the nutritious tundra and moving about to escape hordes of mosquitoes.
By late July, the Porcupine herd begins to leave the vast tundra plain and heads to the northern foothills of the Brooks Range where they now endure biting flies (warble and nose-bot flies) that deposit larvae in their hide and nostrils, respectively. The fall migration ensues by late August and the 2-week rut occurs in October, as frenzied bulls forego eating to gather and impregnate their harem. While some of the herd remains within the Brooks and British Mountains, most head for the Richardson and Ogilvie Mountains of the Yukon Terrority, in the upper reaches of the Porcupine River. Their neighbors, the Central Arctic Caribou herd, numbering about 20,000 individuals, have a much shorter migration, wintering in the Brooks Range and summering on the Coastal Plain. Both herds are threatened by global warming and by human development across their territories, especially the ongoing political pressure to drill on the Arctic NWR.
After wintering in mountainous regions south and east of the Brooks Range, the Porcupine Caribou begin their spring migration in March, led by cows and yearlings (bulls and juveniles follow a few weeks later). Using three primary routes across the Brooks Range of Alaska and British Mountains of the northern Yukon, pregnant cows reach the North Slope by late May and calving begins, synchronized to reduce the impact of predation by wolves, grizzlies and golden eagles; the formation of nursery groups and the rapid development of calves (able to run within 24 hours) also serve to diminish loss of the newborns. As the bulls and juveniles arrive, the caribou assemble in huge herds, feeding on the nutritious tundra and moving about to escape hordes of mosquitoes.
By late July, the Porcupine herd begins to leave the vast tundra plain and heads to the northern foothills of the Brooks Range where they now endure biting flies (warble and nose-bot flies) that deposit larvae in their hide and nostrils, respectively. The fall migration ensues by late August and the 2-week rut occurs in October, as frenzied bulls forego eating to gather and impregnate their harem. While some of the herd remains within the Brooks and British Mountains, most head for the Richardson and Ogilvie Mountains of the Yukon Terrority, in the upper reaches of the Porcupine River. Their neighbors, the Central Arctic Caribou herd, numbering about 20,000 individuals, have a much shorter migration, wintering in the Brooks Range and summering on the Coastal Plain. Both herds are threatened by global warming and by human development across their territories, especially the ongoing political pressure to drill on the Arctic NWR.
Kamis, 05 Januari 2012
The Arctic Falcon
Gyrfalcons are the largest and most powerful falcons on our planet, inhabiting Arctic and Subarctic regions of the globe. Those that live near or above the Arctic Circle are white or pale gray in color while more southern subspecies have various degrees of gray or brown in their plumage.
Solitary for much of the year, adult males and females pair up in March and a clutch of eggs is laid by late April, usually on a bare rock ledge or perhaps in an abandoned raven nest. Both parents incubate the eggs and, within two weeks of hatching, the downy young are left to endure the harsh northern climate while the parents hunt for food; it is then that gyrfalcons are most vulnerable to predation, usually by ravens, skuas or Arctic fox. Those that survive to adulthood have little to fear from natural predators; swift, powerful and agile, they are imposing rivals and may live for 20 years or more.
Gyrfalcons feed primarily on ptarmigan but also attack geese, ducks, gulls and a variety of Arctic songbirds; tundra residents such as Arctic hares, ground squirrels and lemmings are also potential victims. These magnificent raptors, in the style of great white sharks, initially stun their prey with a traumatic collision or chase them to ground before making the kill. During the colder months, gyrfalcons are known to hunt along the pack ice, oblivious to the frigid conditions; though nonmigratory, a few may turn up across the northernmost U.S. in mid to late winter.
Solitary for much of the year, adult males and females pair up in March and a clutch of eggs is laid by late April, usually on a bare rock ledge or perhaps in an abandoned raven nest. Both parents incubate the eggs and, within two weeks of hatching, the downy young are left to endure the harsh northern climate while the parents hunt for food; it is then that gyrfalcons are most vulnerable to predation, usually by ravens, skuas or Arctic fox. Those that survive to adulthood have little to fear from natural predators; swift, powerful and agile, they are imposing rivals and may live for 20 years or more.
Gyrfalcons feed primarily on ptarmigan but also attack geese, ducks, gulls and a variety of Arctic songbirds; tundra residents such as Arctic hares, ground squirrels and lemmings are also potential victims. These magnificent raptors, in the style of great white sharks, initially stun their prey with a traumatic collision or chase them to ground before making the kill. During the colder months, gyrfalcons are known to hunt along the pack ice, oblivious to the frigid conditions; though nonmigratory, a few may turn up across the northernmost U.S. in mid to late winter.
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