Coral bleaching poses a threat not only to fragile reefs but to entire marine ecosystems as well. Photo Credit: www.globalcoralbleaching.org

Coral bleaching is bad news for fragile marine ecosystems. Mass bleaching of corals on a wide scale is worse news still. Yet bleaching en masse reefs around the seas are, according to scientists who have surveyed bleaching records of 100 reefs collected between 1980 and 2016 from around the tropics.

The researchers, who have published their findings in the journal Science, have found that reefs are bleaching with far more frequency than ever before in recorded memory. Worse: more frequent episodes of mass bleaching allows fragile corals less time to recover. The culprit for this phenomenon is the usual suspect: climate change that increases water temperatures.

Read more: Coral Reefs are getting KO’d by Climate Change


The Collins glacier on King George Island in the Antarctic has retreated in the last 10 years and shows signs of fragility. AFP photo

Antarctica:  A decade ago, a thick layer of ice covered the Collins Glacier on Antarctica’s King George Island.

Now, the rocky landscape is visible to the naked eye, in a region that is both a victim of and a laboratory for climate change.

Read more: Antarctica: a laboratory for climate change


The coastal city of San Juan in Puerto Rico was flooded after Hurricane Maria hit in September 2017.Credit: Dennis M. Rivera Pichardo/The Washington Post/Getty

Cities must address climate change. More than half of the world’s population is urban, and cities emit 75% of all carbon dioxide from energy use 1. Meeting the target of the 2015 Paris climate agreement to keep warming well below 2° C above pre-industrial levels requires staying within a ‘carbon budget’ and emitting no more than around 800 gigatonnes of CO2 in total after 2017. Yet bringing the rest of the world up to the same infrastructure level as developed countries (those listed as Annex 1 to the Kyoto Protocol) by 2050 could take up to 350 gigatonnes of the remaining global carbon budget 2. Much of this growth will be in cities in the developing world (see ‘Urban development challenge’).

Cities are increasingly feeling the effects of extreme weather. Many are located on floodplains, in dry areas or on coasts. In 2017, more than 1,000 people died and 45 million people lost homes, livelihoods, and services when severe floods hit southeast Asian cities, including Dhaka in Bangladesh and Mumbai in India. California’s suburbs and Rio de Janeiro in Brazil have experienced floods and mudslides on the heels of drought, wildfires and heavy rains. Cape Town in South Africa has endured extreme drought since 2015. By 2030, millions of people and US$4 trillion of assets will be at risk from such events (see go.nature.com/2sbj4qh).

Read more: Six research priorities for cities and climate change


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