The Natural World

Wonders of Nature - Taiga: The Boreal Forest Taiga is a biome characterized by coniferous forests. Covering most of inland Alaska, Canada, Sweden, Finland, inland Norway, northern Kazakhstan and Russia (especially Siberia), as well as parts of the extreme northern continental United States, the taiga is the world's largest terrestrial biome. In Canada, boreal forest is the term used to refer to the southern part of this biome, while "taiga" is used to describe the more barren northern areas south of the Arctic tree-line.

Since North America and Eurasia were recently connected by the Bering land bridge, a number of animal and plant species (more animals than plants) were able to colonise both continents and are distributed throughout the taiga biome. Others differ regionally, typically with each genus having several distinct species, each occupying different regions of the taiga. Taigas also have some small-leaved deciduous trees like birch, alder, willow and aspen; mostly in areas escaping the most extreme winter cold. However, the deciduous Larch is coping with the coldest winters on the northern hemisphere in eastern Siberia. The southernmost part of the taiga also have trees like oak, maple and elm scattered among the conifers.
The taiga biome has a harsh continental climate with a very large temperature range between summer and winter, classified as "Dfc" or "Dfb" in the Köppen climate classification scheme. Aside from the tundra and permanent ice caps, it is the coldest biome on Earth. High latitudes mean that, for much of the year the sun does not rise far above the horizon; winters last at least 5-6 months, with average temperatures below freezing. Temperatures vary from –50°C to 30°C throughout the whole year, with eight or more months of temperatures averaging below 10°C. The summers, while short, are generally warm and humid. In general, taiga grows north to the 10°C July isotherm, occasionally to the 9°C July isotherm (Arno & Hammerly 1984, Arno et al. 1995). The southern limit is more variable, depending on rainfall; taiga may be replaced by open steppe woodland south of the 15°C July isotherm where rainfall is very low, but more typically extends south to the 18°C July isotherm, and locally where rainfall is higher (notably in eastern Siberia and adjacent northern Manchuria) south to the 20°C July isotherm. In these warmer areas, the taiga has higher species diversity with more warmth-loving species such as Korean Pine, Jezo Spruce and Manchurian Fir, and merges gradually into mixed temperate forest, or more locally (on the Pacific Ocean coasts of North America and Asia) into coniferous temperate rainforests.

The taiga experiences relatively low precipitation throughout the year (200–750 mm annually), primarily as rain during the summer months, but also as fog and snow; as evaporation is also low for most of the year, precipitation exceeds evaporation and is sufficient for dense vegetation growth. Snow may remain on the ground for as long as nine months in the northernmost extensions of the taiga ecozone (Sayre, 16).

Much of the area currently classified as taiga was recently glaciated. As the glaciers receded, they left depressions in the topography that have since filled with water, creating lakes and bogs (especially muskeg soil), found throughout the taiga.

Taiga soil tends to be young and nutrient-poor; it lacks the deep, organically-enriched profile present in temperate deciduous forests (Sayre, 19). The thinness of the soil is due largely to the cold; it hinders the development of soil, as well as the ease with which plants can use its nutrients (Sayre, 19). Fallen leaves and moss can remain on the forest floor for a long time in the cool, moist climate, which limits their organic contribution to the soil; acids from evergreen needles further leach the soil, creating spodosol (Sayre, 19-20). Since the soil is acidic due to the falling pine needles, the forest floor has only lichens and some mosses growing on it.
The taiga is home to a number of large herbivorous mammals and smaller rodents. These animals have also adapted to survive the harsh climate. Some of the larger mammals, such as bears, eat during the summer in order to gain weight and then go into hibernation during the winter. Other animals have adapted layers of fur or feathers to insulate them from the cold.

Due to the climate, carnivorous diets are an inefficient means of obtaining energy; energy is limited, and most energy is lost between trophic levels. However, predatory birds (owls and eagles) and other smaller carnivores, including foxes and weasels, feed on the rodents. Larger carnivores, such as lynxes and wolves, prey on the larger animals. Omnivores, such as bears and raccoons are fairly common, sometimes picking through human garbage.
A considerable number of birds such as Siberian Thrush, White's Thrush and Dark-throated Thrush, migrate to this habitat to take advantage of the long summer days and abundance of insects found around the numerous bogs and lakes. Of the perhaps 300 species of birds that summer in the taiga, only 30 stay for the winter (Sayre, 28). These are either carrion-feeding or large raptors that can take live mammal prey, including Golden Eagle, Rough-legged Buzzard, and Raven, or else seed-eating birds, including several species of grouse and crossbills.


Mountain glaciers are shrinking three times faster than they were in the 1980s, scientists have announced.
The World Glacier Monitoring Service, which continuously studies a sample of 30 glaciers around the world, says the acceleration is down to climate change. Its announcement came as climate scientists convened in Paris to decide the final wording of a major report. There is reported to be some disagreement over what forecasts they will make for sea level rise. But whatever form of words they agree on, the Intergovernmental Panel on Climate Change (IPCC) will declare that human-induced climate change is happening and needs to be tackled.

We will enter conditions which we have not seen in the past 10,000 years, and perhaps conditions which mankind has never experienced

Wilfried Haeberli, WGMS

"[The report] embodies substantial new research, it addresses gaps that existed in our knowledge earlier, it has reduced existing uncertainties," IPCC chairman Rajendra Pachauri told reporters at a news briefing in Paris. "I hope policies and actions will be formed to address the problem." The report, due out on Friday, forms the first part of the IPCC's Fourth Assessment Report, and will be the latest definitive assessment of climate science. Melting away Of all the various features that make up the surface of the Earth, glaciers are perhaps showing the starkest signs of rising temperatures. The World Glacier Monitoring Service (WGMS), based in Switzerland, continuously studies a set of 30 mountain glaciers in different parts of the world. It is not quite a representative sample of all mountain glaciers, but does give a reliable indication of global trends.

MOUNTAIN GLACIERS DECLINE Data comes from sample of 30 mountain glaciers Glaciers have different densities, so thinning is expressed in metres of water equivalent (mwe) One mwe is roughly equivalent to 1.1m of ice

The latest survey, just released, shows accelerating decline. During 2005, this sample of 30 glaciers became, on average, 60-70cm thinner. This figure is 1.6 times more than the average annual loss during the 1990s, and three times faster than in the 1980s. With mountain glaciers typically only tens of metres thick, this meant, said WGMS director Wilfried Haeberli, that many would disappear on a timescale of decades if the trend continued. "We can say there were times during the warmer periods of the last 10,000 years when glaciers have been comparable to what they are now," he told the BBC News website. "But it is not the past that worries us, it is the future. With the scenarios predicted, we will enter conditions which we have not seen in the past 10,000 years, and perhaps conditions which mankind has never experienced." Last year, WGMS scientists forecast that the Alps would lose up to three-quarters of their glaciers during the coming century. The WGMS is closely allied to the United Nations Environment Programme, whose executive director Achim Steiner commented: "Glaciers are important sources of water for many important rivers upon which people depend for drinking water, agriculture and industrial purposes. "The findings... should strengthen the resolve of governments to act now to reduce greenhouse gas emissions." Rough seas The IPCC report due out on Friday is likely to contain stronger wording than its previous assessment, in 2001, on the likelihood that human activities are principally responsible for the climatic changes observed around the world.

Campaigners have sent a message to IPCC scientists meeting in Paris

The 2001 report forecast that by the end of this century, temperatures would have risen by between 1.4C and 5.8C. The new report is likely to reduce the range of uncertainty, though not rule out the possibility entirely of increases in the order of 5.8C. But there is reported to be disagreement over the wording on expected sea level rise. A bigger network of tide gauges and other instruments has enabled researchers to conclude that the sea level is on average rising by about 2mm per year, or 20cm per century. This is one of the factors which led to earlier drafts of this report projecting rises by the end of the century which were a lot less than the maximum figure of 88cm contained in the 2001 version. But some scientists are arguing that recent observations of the Greenland and West Antarctic ice sheets suggest a major melt may be commencing. This, they say, should be reflected in the eventual IPCC projections.



 

Action urged to protect deep seas I spent most of my time when I was as an Oceanographer working on the impact of marine deep sea fisheries on the environment. My work involved  trying to influence the review of the European Common Fisheries Policy to include more environmental protection. When the contract ended we looked back and felt that we had made a difference. However  5 years after the end of the review I look back and see little change, if anything, internationally things are worse. Urgent action is needed to protect the world's oceans from human exploitation, according to conservationists.   Fish with high commercial value are in decline

They say over-fishing, pollution and climate change are pushing marine areas to the point of no return. The warning comes from the United Nations Environment Programme (Unep) and World Conservation Union (IUCN). In a report launched on Friday in New York, they are calling for new marine protected areas to be set up in deep seas and open oceans. Dr Stefan Hain from Unep said it was a crucial moment for the marine environment. "Very often, it's the case that people go out there and fish without considering what effect this has on the fish stocks," he said. "We know now that the environments and the eco-systems in the deep water are very fragile. "The impact is that these stocks are being reduced at an alarming rate, and, simply, these ecosystems are not designed to cope with drastic impact by human activity." Beyond limits The report, Ecosystems and Biodiversity in Deep Waters and High Seas, is the centrepiece of talks on the law of the sea at the UN. THREATENED WATERS Illegal long-line fishing kills more than 300,000 seabirds each year Large fish like tuna, cod and swordfish have declined by as much as 90% in the past century  Over 46,000 pieces of plastic litter are floating on every square mile of the ocean The report makes the case for marine protected areas in parts of the sea that are not included in the territorial sea or in the internal waters of a State. Ibrahim Thiaw, acting director general of the IUCN, said well over 60% of the marine world and its rich biodiversity, found beyond the limits of national jurisdiction, was vulnerable and at increasing risk. "Governments must urgently develop the guidelines, rules and actions needed to bridge this gulf," he said. "Otherwise we stand to lose and to irrevocably damage unique wildlife and critical ecosystems many of which moderate our very existence on the planet." Deep-sea fish stocks 'plundered' Fish stocks in international waters are being plundered to the point of extinction, a leading conservationist group has said. Illegal fishing and bottom-trawling in deep waters are to blame, according to a report from WWF. It says the current system of regional fishing regulation is failing to tackle the problem, with not enough being done to enforce quotas or replenish stocks. It says species under severe threat include tuna and the orange roughy. The orange roughy is targeted by bottom-trawlers, which drag heavy rollers over the ocean floor, destroying coral and other ecosystems. Coral clearance: Bottom trawling and its bycatch and impacts The seabed before and after trawling "Given the perilous overall state of marine fisheries resources and the continuing threats posed to the marine environment from over-fishing and damaging fishing activity, the need for action is immediate," Simon Cripps, director of WWF's global marine programme, said. Illegal fishing "by highly mobile fleets under the control of multinational companies" was identified as one of the worst threats to marine life. When I was studying for my Masters Degree I did my Dissertation of the effectiveness of the international fisheries commissions which govern the fishing in international waters, 10 years on i see little change and if any thing the situation is much more critical. Map of proposed and existing fishery protection areas But the report also attacked governments for over fishing. "Vast over-capacity in authorised fleets, over-fishing of stocks... the virtual absence of robust rebuilding strategies... and a lack of precaution where information is lacking or uncertain are all characteristic of the management regimes currently in place," it said. No enforcement The report was released ahead of a New York meeting on the United Nations Fish Stocks Agreement, the legal framework for the management of fish stocks on the high seas, next week. BBC science reporter Matt McGrath says that on the high seas - away from the protection of national quotas - fish stocks are at their most vulnerable. It's got to stop, we've got to do it quickly. There is hope, if we can get management put in place Simon Cripps WWF global marine programme Read the WWF report [1.3mb] Fishing regulators 'failing' 'Ban destructive fishing' call The regulation of fishing in these international waters is the responsibility of regional fishing management organisations - made up of countries with a vested interest in the area. According to WWF, most are failing to manage fish stocks in a sustainable way. Decision-making is poor, it says, and the regional organisations are powerless to control the activities of countries who ignore regulations. This backs up the conclusions of an analysis last year from the conservation group BirdLife International, which concluded that a majority of the regional fisheries organisations are failing to take their responsibilities seriously. The authors are calling on the United Nations to review fishing on the high seas and strengthen the resolve of regional authorities to deal with states that flout agreements. "It's got to stop, we've got to do it quickly," Mr Cripps said. "There is hope, if we can get management put in place." Impact of Bottom Trawling on the Seabed