a large fraction of terrestrial and freshwater species. at 1.2 °c (2.2 °f) of warming (around 2023) some ecosystems are threatened by mass die-offs of trees and from heatwaves. at 2 °c (3.6 °f) of warming, around 10% of species on land would become critically endangered. this differs by group: for instance insects and salamanders are more vulnerable.: 259 the rate of global tree cover loss has approximately doubled since 2001, to an annual loss approaching an area the size of italy. rainfall on the amazon rainforest is recycled when it evaporates back into the atmosphere instead of running off away from the rainforest. this water is essential for sustaining the rainforest. due to deforestation the rainforest is losing this ability, exacerbated by climate change which brings more frequent droughts to the area. the higher frequency of droughts seen in the first two decades of the 21st century, as well as other data, signal that a tipping point from rainforest to savanna might be close. a 2019 study concluded that this ecosystem could begin a 50-years-long collapse to a savanna around 2021, after which it would become increasingly and disproportionally more difficult to prevent or reverse this shift. marine ecosystems marine heatwaves are happening more often and have widespread impacts on life in the oceans, such as mass dying events and coral bleaching. harmful algae blooms have increased in response to warming waters, loss of oxygen and eutrophication. melting sea ice destroys habitat, including for algae that grows on its underside. ocean acidification has a range of potentially harmful effects for marine organisms. shell-forming organisms like oysters are particularly vulnerable, while some phytoplankton and seagrass species may benefit. however, this also includes toxic to fish phytoplankton species, whose spread poses risks to fisheries and aquaculture. combatting pollution can reduce the impacts of acidification. warm water coral reefs are very sensitive to global warming and ocean acidification. coral reefs provide a habitat for thousands of species, and ecosystem services such as coastal protection and food. the resilience of reefs can be improved by curbing local pollution and overfishing, but 70–90% of today's warm water coral reefs will disappear even if warming is kept to 1.5 °c (2.7 °f). coral reefs are framework organisms: they build physical structures that form habitats for other sea creatures. other framework organisms are also at risk from climate change. for instance, mangroves and seagrass are considered to be at moderate risk for lower levels of global warming. tipping points and irreversible impacts possible tipping elements in the climate system self-reinforcing feedbacks can amplify climate change. the climate system exhibits "threshold behaviour" or tipping points when these feedbacks lead parts of the earth system into a new state, such as the runaway loss of ice sheets or the dieback of forests. tipping behaviour is found across the climate system, in ecosystems, ice sheets, and the circulation of the ocean and atmosphere. tipping points are studied using data from earth's distant past and by physical modelling. there is already moderate risk of global tipping points at 1 °c (1.8 °f) above pre-industrial temperatures, and that risk becomes high at 2.5 °c (4.5 °f). it is possible that some tipping points are close to being crossed or have already been crossed, like those of the west antarctic and greenland ice sheets, the amazon rainforest and warm-water coral reefs. tipping points are "perhaps the most 'dangerous' aspect of future climate changes", leading to irreversible impacts on society. for instance, a collapse of the atlantic meridional overturning circulation would likely halve rainfall in india, and lead to severe drops in temperature in northern europe. many tipping points are interlinked, so that triggering one may lead to a cascade of effects, even well below 2 °c (3.6 °f) of warming. a 2018 study states that 45% of environmental problems, including those caused by climate change, are interconnected and make the risk of a domino effect bigger. there are further impacts that may be irreversible, at least over the timescale of many human generations. in the physical environment, this includes warming of the deep ocean and acidification, which are set to continue even when global temperatures stop rising. in biological systems, the extinction of species would be an irreversible impact. in social systems, unique cultures may be lost or the disappearance of endangered languages may be exacerbated due to climate change. health, food security and water security health this section is an excerpt from effects of climate change on human health. the effects of climate change on human health are increasingly well studied and quantified. they fall into three main categories: (i) direct effects (e.g. due to heat waves, extreme weather events), (ii) impacts from climate-related changes in ecological systems and relationships (e.g. crop yields, marine productivity), and (iii) the more indirect consequences such as impoverishment, displacement, and mental health problems. more specifically, the relationship between health and heat includes the following main aspects: exposure of vulnerable populations to heatwaves, heat-related mortality, reduced labour capacity for outdoor workers and impacts on mental health. there is a range of climate-sensitive infectious diseases which may increase in some regions, such as mosquito-borne diseases, cholera and some waterborne diseases. health is also acutely impacted by extreme weather events (floods, hurricanes, droughts, wildfires) through injuries, diseases, and air pollution in the case of wildfires. other indirect health impacts from climate change may be rising food insecurity, undernutrition and water insecurity. this section is an excerpt from effects of climate change on mental health. part of a series onclimate change andsociety effects mitigation adaptation economics business action climate finance economic impacts economics of mitigation emissions trading low-carbon economy social issues agriculture cities climate justice children ethics gender indigenous people fisheries human rights security poverty migration women health and psychology climate grief eco-anxiety infectious diseases mental health psychology of denial waterborne diseases communication carbon literacy climate crisis education media coverage popular culture fiction art games public opinion adaptation resilience vulnerability disaster risk reduction ecosystem-based adaptation flood control politics history political economy climate governance climate movement denial global warming controversy litigation individual actions unfccc un conferences kyoto protocol paris agreement portal glossary index the effects of climate change on mental health and well-being can be negative, especially for vulnerable populations and those with pre-existing serious mental illness. there are three broad pathways by which these effects can take place: directly, indirectly or via awareness. the direct pathway includes stress related conditions being caused by exposure to extreme weather events, such as post-traumatic stress disorder (ptsd). scientific studies have linked mental health outcomes to several climate-related exposures—heat, humidity, rainfall, drought, wildfires and floods. the indirect pathway can be via disruption to economic and social activities, such as when an area of farmland is less able to produce food. the third pathway can be of mere awareness of the climate change threat, even by individuals who are not otherwise affected by it. mental health outcomes have been measured in several studies through indicators such as psychiatric hospital admissions, mortality, self-harm and suicide rates. vulnerable populations and life stages include people with pre-existing mental illness, indigenous peoples, children and adolescents. the emotional responses to the threat of climate change can include eco-anxiety, ecological grief and eco-anger. such emotions can be rational responses to the degradation of the natural world and lead to adaptive action. food security climate change will impact agriculture and food production around the world due to the effects of elevated co2 in the atmosphere; higher temperatures; altered precipitation and transpiration regimes; increased frequency of extreme events; and modified weed, pest, and pathogen pressure. droughts result in crop failures and the loss of pasture for livestock. loss and poor growth of livestock cause milk yield and meat production to decrease. the rate of soil erosion is 10–20 times higher than the rate of soil accumulation in agricultural areas that use no-till farming. in areas with tilling it is 100 times higher. climate change makes this type of land degradation and desertification worse.: 5 climate change is projected to negatively affect all four pillars of food security: not only how much food is available, but also how easy food is to access (prices), food quality, and how stable the food system is. for example, climate change is already affecting the productivity of wheat and other key staples. in many areas, fisheries have already seen their catch decrease because of global warming and changes in biochemical cycles. in combination with overfishing, warming waters decrease the amount of fish in the ocean.: 12 per degree of warming, ocean biomass is expected to decrease by about 5%. tropical and subtropical oceans are most affected, while there may be more fish in polar waters. water security water resources can be affected by climate change in various ways. the total amount of freshwater available can change, for instance due to dry spells or droughts. heavy rainfall and flooding can have an impact on water quality: pollutants can be transported into water bodies by the increased surface runoff. in coastal regions, more salt may find its way into water resources due to higher sea levels and more intense storms. higher temperatures also directly degrade water quality: warm water contains less oxygen. changes in the water cycle threaten existing and future water infrastructure. it will be harder to plan investments for water infrastructure as there are significant uncertainties about future variability of the water cycle. between 1.5 and 2.5 billion people live in areas with regular water security issues. if global warming reaches 4 °c (7.2 °f), water insecurity would affect about twice as many people. water resources are projected to decrease in most dry subtropical regions and mid-latitudes, but increase in high latitudes. however, as streamflow becomes more variable, even regions with increased water resources can experience additional short-term shortages. the arid regions of india, china, the us and africa are already seeing dry spells and drought impact water availability. human settlement the arctic, africa, small islands, asian megadeltas and the middle east are regions that are likely to be especially affected by climate change. low-latitude, less-developed regions are at most risk of experiencing negative impacts due to climate change. the ten countries of the association of southeast asian nations (asean) are among the most vulnerable in the world to the negative effects of climate change, however asean's climate mitigation efforts are not in proportion to the climate change threats the region faces. impacts from heat overlap between future population distribution and extreme heat in a high emission scenarioregions inhabited by a third of the human population could become as hot as the hottest parts of the sahara within 50 years without a change in patterns of population growth and without migration, if greenhouse gas emissions continue to grow rapidly. the projected average temperature of above 29 °c (84 °f) for these regions would be outside the "human temperature niche" – a suggested range for climate biologically suitable for humans based on historical data of mean annual temperatures – and the most affected regions have little adaptive capacity. increased extreme heat exposure from both climate change and the urban heat island effect threatens urban settlements. this is made worse by the loss of shade from urban trees that cannot withstand the heat stress. in 2019, the crowther lab from eth zurich paired the climatic conditions of 520 major cities worldwide with the predicted climatic conditions of cities in 2050. 22% of the major cities are predicted to have climatic conditions that do not exist in any city today. for instance, 2050 london will have a climate similar to 2019 melbourne in australia, athens and madrid like fez in morocco, and nairobi in kenya like maputo in mozambique. the indian city pune will be like bamako in mali, bamako will be like niamey in niger. brasilia will be like goiania, both in brazil. low-lying coastal regions low-lying cities and other settlements near the sea face multiple simultaneous risks from climate change. besides flooding risks from sea level rise, they may face impacts from more severe storms, ocean acidification, and salt intrusion into the groundwater. societal changes increase the risks that these regions face, such as continued development in exposed areas. floodplains and low-lying coastal areas will flood more frequently due to climate change, like this area of