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This article is about climate change and ecosystems. ==Impacts== Unchecked global warming could affect most terrestrial ecoregions. Increasing global temperature means that ecosystems will change; some species are being forced out of their habitats (possibly to extinction) because of changing conditions, while others are flourishing. Secondary effects of global warming, such as lessened snow cover, rising sea levels, and weather changes, may influence not only human activities but also the ecosystem. For the IPCC Fourth Assessment Report, experts assessed the literature on the impacts of climate change on ecosystems. Rosenzweig ''et al''. (2007) concluded that over the last three decades, human-induced warming had likely had a discernible influence on many physical and biological systems (p. 81). Schneider ''et al''. (2007) concluded, with very high confidence, that regional temperature trends had already affected species and ecosystems around the world (p. 792). With high confidence, they concluded that climate change would result in the extinction of many species and a reduction in the diversity of ecosystems (p. 792). *Terrestrial ecosystems and biodiversity: With a warming of 3°C, relative to 1990 levels, it is likely that global terrestrial vegetation would become a net source of carbon (Schneider ''et al''., 2007:792). With high confidence, Schneider ''et al''. (2007:788) concluded that a global mean temperature increase of around 4°C (above the 1990-2000 level) by 2100 would lead to major extinctions around the globe. *Marine ecosystems and biodiversity: With very high confidence, Schneider ''et al''. (2007:792) concluded that a warming of 2°C above 1990 levels would result in mass mortality of coral reefs globally. *Freshwater ecosystems: Above about a 4°C increase in global mean temperature by 2100 (relative to 1990-2000), Schneider ''et al''. (2007:789) concluded, with high confidence, that many freshwater species would become extinct. Studying the association between Earth climate and extinctions over the past 520 million years, scientists from the University of York write, "The global temperatures predicted for the coming centuries may trigger a new ‘mass extinction event’, where over 50 per cent of animal and plant species would be wiped out." Many of the species at risk are Arctic and Antarctic fauna such as polar bears and emperor penguins. In the Arctic, the waters of Hudson Bay are ice-free for three weeks longer than they were thirty years ago, affecting polar bears, which prefer to hunt on sea ice.〔(On Thinning Ice ) ''Michael Byers'' London Review of Books January 2005〕 Species that rely on cold weather conditions such as gyrfalcons, and snowy owls that prey on lemmings that use the cold winter to their advantage may be hit hard. Marine invertebrates enjoy peak growth at the temperatures they have adapted to, regardless of how cold these may be, and cold-blooded animals found at greater latitudes and altitudes generally grow faster to compensate for the short growing season.〔 〕 Warmer-than-ideal conditions result in higher metabolism and consequent reductions in body size despite increased foraging, which in turn elevates the risk of predation. Indeed, even a slight increase in temperature during development impairs growth efficiency and survival rate in rainbow trout.〔 〕 Rising temperatures are beginning to have a noticeable impact on birds, and butterflies have shifted their ranges northward by 200 km in Europe and North America. Plants lag behind, and larger animals' migration is slowed down by cities and roads. In Britain, spring butterflies are appearing an average of 6 days earlier than two decades ago. A 2002 article in ''Nature''〔 〕 surveyed the scientific literature to find recent changes in range or seasonal behaviour by plant and animal species. Of species showing recent change, 4 out of 5 shifted their ranges towards the poles or higher altitudes, creating "refugee species". Frogs were breeding, flowers blossoming and birds migrating an average 2.3 days earlier each decade; butterflies, birds and plants moving towards the poles by 6.1 km per decade. A 2005 study concludes human activity is the cause of the temperature rise and resultant changing species behaviour, and links these effects with the predictions of climate models to provide validation for them.〔(''www.stanford.edu'' )〕 Scientists have observed that Antarctic hair grass is colonizing areas of Antarctica where previously their survival range was limited.〔(Grass flourishes in warmer Antarctic ) originally from The Times, December 2004〕 Mechanistic studies have documented extinctions due to recent climate change: McLaughlin ''et al.'' documented two populations of Bay checkerspot butterfly being threatened by precipitation change.〔 〕 Parmesan states, "Few studies have been conducted at a scale that encompasses an entire species"〔 〕 and McLaughlin ''et al.'' agreed "few mechanistic studies have linked extinctions to recent climate change."〔 Daniel Botkin and other authors in one study believe that projected rates of extinction are overestimated. For "recent" extinctions, see Holocene extinction. Many species of freshwater and saltwater plants and animals are dependent on glacier-fed waters to ensure a cold water habitat that they have adapted to. Some species of freshwater fish need cold water to survive and to reproduce, and this is especially true with salmon and cutthroat trout. Reduced glacier runoff can lead to insufficient stream flow to allow these species to thrive. Ocean krill, a cornerstone species, prefer cold water and are the primary food source for aquatic mammals such as the blue whale. Alterations to the ocean currents, due to increased freshwater inputs from glacier melt, and the potential alterations to thermohaline circulation of the worlds oceans, may affect existing fisheries upon which humans depend as well. The ''white lemuroid possum'', only found in the Daintree mountain forests of northern Queensland, may be the first mammal species to be driven extinct by global warming in Australia. In 2008, the white possum has not been seen in over three years. The possums cannot survive extended temperatures over , which occurred in 2005. A 27-year study of the largest colony of Magellanic penguins in the world, published in 2014, found that extreme weather caused by climate change is responsible for killing 7% of penguin chicks per year on average, and in some years studied climate change accounted for up to 50% of all chick deaths. Since 1987, the number of breeding pairs in the colony has reduced by 24%. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Climate change and ecosystems」の詳細全文を読む スポンサード リンク
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