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Science
| 04/05/18

UN: biodiversity loss as big a threat as climate change

TCE

Dramatic biodiversity declines in every region of the world represent an existential crisis facing civilization rivalling or perhaps even surpassing that of global warming, argue the authors of a three-year, UN-backed assessment of the scale of the problem.

And the two issues are interlinked, they add, forecasting that by 2050, climate change will begin to surpass land-use change as the main driver of human-caused extinctions. This process will occur both directly from temperature changes and ocean acidification due to increased atmospheric CO2 concentration, and indirectly as climate change amplifies the impacts of habitat losses.

Geologically rapid regional changes in temperature of the atmosphere and the ocean are driving changes in glacial extent, rainfall, river discharge, wind and ocean currents and sea level, which have had negative impacts on biodiversity. Ocean acidification meanwhile is affecting key marine species and major components of important ocean food webs. This in turn combines with other human-induced stresses such as deoxygenation in the upper water column due to nutrient run-off from farming to exacerbate the situation.

These are two of the key messages from four regional reports weaved together over three years by 550 researchers from around the globe assessing some 10,000 separate scientific papers and coordinated by the UN’s Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES). The 129-member nation organization does for biodiversity what the Intergovernmental Panel on Climate Change does for global warming: assess the state of the science about a problem and draw upon an evidence base across disciplines beyond the natural sciences to describe a suite of solution options.

The recently-released reports note that while the extent of conservation areas has increased over time, governments are at risk of not meeting biodiversity targets first set at a 2010 UN conference. Highlights include that 42 percent of terrestrial species across Europe have experienced declines in the last decade alone and that based on current trends, all exploitable fisheries are set to collapse by 2048 in the Asia-Pacific region.

So, what is biodiversity anyway? Biological diversity is the contemporary term that replaces earlier terms such as “species richness,” not least as it describes diversity not merely at the level of species, but also at the genetic and ecosystem levels (amongst other frames). Biodiversity is richest in the tropics where it is warmest. Some 90 percent of the world’s species live in tropical forests alone. Biodiversity has steadily increased over time despite “mass extinctions.” But at the end of the last ice age, humans were the authors of extinctions of numerous large animals (“megafauna”) everywhere we went. Some researchers believe we are now on the cusp of another mass extinction event.

If more increased temperature means more biodiversity, why wouldn’t global warming be a boon for biodiversity? Past epochs of global warming show increases in biodiversity, and when temperatures fell, biodiversity declined. But these occurred over thousands or millions of years, giving organisms time to evolve. Anthropogenic global warming is happening over the course of mere decades: a rate of change too fast for many species.

The IPBES authors argue that we all should be tackling this issue at the same level of international seriousness with which we currently address climate change because the deterioration of biodiversity is undermining the ability of the rest of nature to provide to us food, water, clothing, housing and other necessities they call “ecosystem services.” For example, some 2.5 billion people depend upon seafood as their main source of protein, but the total global catch from wild fisheries has fallen year-on-year since its peak in 1996.

The importance of biodiversity in provision of the ecosystem services upon which human civilization depends was first recognized at the international level via 1992’s Convention on Biological Diversity, backed by more than 190 countries. The IPBES was borne out of this process.

Until the advent of climate change, the most significant driver had been habitat loss, primarily as a result of expansion of agriculture and deforestation. The species that are able to thrive in the new anthropogenic environmental niches are hardy but fewer in number, and may not provide the same ecological services.

While there are myriad solutions, the common thread through them all is a retreat from such pressures on habitat. This can take the form of expansion of protected areas, constructing networks of wildlife corridors, restoration and reintroduction of wild species or “re-wilding,” sustainable fisheries and agricultural practices, and, with respect to the climate change challenge, ensuring a rapid transition away from fossil fuels.

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