Climate change has adversely affected terrestrial and marine ecosystems, including tundras, mangroves, coral reefs, and caves. Increasing global temperature, more frequent occurrence of extreme weather, and rising sea level are examples of the most impactful effects of climate change. Possible consequences of these effects include species decline and extinction and overall significant loss of biodiversity, change within ecosystems, increased prevalence of invasive species, loss of habitats, forests converting from carbon sinks to carbon sources, ocean acidification, disruption of the water cycle, increased occurrence and severity of natural disasters like wildfires and flooding, and lasting effects on species adaptation.
General
Climate change is affecting terrestrial ecoregions. Increasing global temperature means that ecosystems are changing; some species are being forced out of their habitats (possibly to extinction) because of changing conditions. An example is migration. Due to the ever hotter weather, birds are forced to move to foreign lands. Other effects of global warming include less snow fall, rising sea levels, Ozone depleting and weather changes. These may influence human activities and the ecosystem.
Within 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). They also concluded that climate change would result in the extinction of many species and a reduction in the diversity of different types of ecosystems (p. 792). Terrestrial ecosystems and biodiversity: With a warming of 4-5 °C, relative to 2010 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 2010–2015) by 2100 would lead to major extinctions around the world. Marine ecosystems and biodiversity: With high confidence, scientists concluded that a warming of 2-3 °C above 2010 levels would result in mass mortality of coral reefs globally. In addition, several studies dealing with planktonic organisms and modelling have shown that temperature plays a transcendental role in marine microbial food webs, which may have a deep influence on the biological carbon pump of marine planktonic pelagic and mesopelagic ecosystems. Freshwater ecosystems: Above about a 4 °C increase in global mean temperature by 2100 (relative to 2010), scientists concluded, with high confidence, that many freshwater species would become extinct or largely endangered.
Biodiversity
Extinction
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 percent 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. 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 negatively affected. Marine invertebrates achieve peak growth at the temperatures they have adapted to, and cold-blooded animals found at high 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.