LONDON (Thomson Reuters Foundation) - A failure to get to grips with climate change and associated problems, from ecosystem collapse to worsening water and food shortages, is the most severe and probable threat facing humanity, more than 200 scientists have warned.

The risks will also likely feed on each other - as intensifying heat and drought spur more wildfires and forest loss, for example - “in ways that might cascade to create a global systemic crisis”, they said in a report.

The situation could become “potentially uncontrollable in the future if we don’t act very soon”, said Owen Gaffney, an author of the report and a sustainability analyst with the Potsdam Institute for Climate Impact Research.

The survey of 222 scientists from more than 50 countries echoes the top worries of economic and business leaders in a risk perceptions report issued last month ahead of the World Economic Forum (WEF) in Davos.

Both this week’s inaugural survey by international sustainability network Future Earth and the WEF report ranked environmental risks as significantly more serious than other threats, from data theft to terrorist attacks and unemployment.

The new survey also examined how social and political trends - such as disinformation campaigns and the rise of populist authoritarian governments - could make efforts to tackle key global challenges more difficult.

Climate threats and associated risks are “very big complex problems that need complex solutions”, Gaffney told the Thomson Reuters Foundation.

Alongside that, “the 2020s need to see the fastest economic transition in history” to curb global warming, added Gaffney, who also works for the Stockholm Resilience Centre.

But a new crop of populist world leaders, including U.S. President Donald Trump, tend to look for simple answers, the report noted.

And disinformation campaigns - backed by everyone from vaccine alarmists to the Russian government in an effort to undermine trust in democratic institutions - can make it hard for voters to understand issues and push for action, it said.

But other forces may help drive the large-scale changes needed, the report said.

Social movements, such as the “Fridays for Future” youth protests spearheaded by Swedish teenager Greta Thunberg, are growing in size and influence, and could exert growing political pressure, Gaffney said.

Another positive sign is Britain’s commitment to achieve net-zero emissions by 2050, despite political upheaval and divisions caused by the country’s decision to leave the European Union, he noted.

“Even in a really difficult political situation there is common ground to do something quite radical,” he said, adding that with Europe now talking about its own Green Deal, the region could reunite, at least around climate policy.

The continuing plunge in the cost of solar and wind power, and their scale-up, also mean clean energy is likely to make ever more economic as well as environmental sense in coming years. “That’s a game changer,” Gaffney said.

But action on environmental risks needs to come quickly, he added.

Scientists have long warned about climate threats but “their speed and severity over the last few years has taken people by surprise” at just 1 degree Celsius of global warming, he said.

The world is currently on track to see average temperatures rise more than 3 degrees Celsius above pre-industrial times this century, a level scientists say would be catastrophic.

“Our actions in the next decade will determine our collective future on Earth,” said Amy Luers, executive director of Future Earth.