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As human pressures on the Earth System accelerate, several critical global, regional and local thresholds are close or have been exceeded. Once these have been passed, abrupt and possibly irreversible changes to the life-support functions of the planet are likely to occur, with significant adverse implications for human well-being. An example of an abrupt change at a regional scale is the collapse of freshwater lake and estuary ecosystems due to eutrophication; an abrupt and irreversible example is the accelerated melting of the Arctic ice-sheet, as well as glacial melt, due to an amplification of global warming (Figure 1). The impacts of complex, non-linear changes in the Earth System are already having serious consequences for human well-being such as:

• multiple and interacting factors, including droughts combined with socio-economic pressures, affect human security;

• increases of average temperature above threshold levels in some places has led to significant human health impacts such as increased incidences of malaria;

• increased frequency and severity of climatic events, such as floods and droughts, to an unprecedented level affect both natural assets and human security;

• accelerating changes of temperature and sea level rise are affecting human well-being in some places. For example, they affect the social cohesion of many communities including indigenous and local ones, and sea level rise poses a threat to some natural assets and the food security of the small island developing states; and

• substantial biodiversity loss and on-going extinction of species are affecting the provision of ecosystem services, such as, the collapse of a number of fisheries and the loss of species used for medicinal purposes.

The prospect of improving human well-being is critically dependent on the capacity of individuals, countries and the international community to respond to environmental changes which increase risks and reduce opportunities for the advancement of human well-being, in particular efforts to eradicate poverty amongst poor and vulnerable populations. Because of the complexities of the Earth System, responses need to focus on the root causes, the underlying drivers of environmental changes, rather than only the pressures or symptoms.

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