Other existential risks include the decline of natural resources (particularly water), human population growth beyond the Earth’s carrying capacity, and nuclear weapons.
Five capital city water storages fell over summer, and some appear to be facing dramatic long-term declines. Late drenching rains fell on southeastern Australia, but some unlucky centres missed out.
The water that replenishes groundwater, rivers and lakes is under threat from climate change, pollution and aging infrastructure.
Parts of Ethiopia will likely be hotter, drier, and more water stressed - with consequences for human and economic development.
Rising sea levels and tectonic activity have eroded the coastlines of the low-lying Carteret Islands in the South Pacific.
Cities relied entirely on conserving and recycling water to get through the last big drought. We now have desalination plants, but getting the most out of our water reserves still makes sense.
Sydney and Melbourne are bringing desalination plants back on stream and Adelaide plans to increase its plant's output. Perth depends on desalination. But is it the best way to achieve water security?
South Africa is a water stressed country but crisis point can be avoided.
Undrinkable drinking water is just one example of how blockades and war have permeated an entire ecosystem.
We think of Canada as a water-rich country, but we are not immune to water shortages or disasters. With some advance planning, Canada can avoid a water catastrophe.
Australian cities have turned to some very costly solutions when water is scarce. But as the world's second-highest users of water per person, more efficient use and recycling are key.
Can community-led research help address Canada's Indigenous water security issues? One project from the Inuit community of Rigolet in Labrador suggests it can.
A reliable water supply from Australia's mountain catchments depends on intact and functioning ecosystems.
A five-year project announced today will implement an innovative water-sensitive approach tailored to informal settlements. The goal is to revitalise 24 communities in Fiji and Indonesia.
The crops of the future must become much better at dealing with dehydration.
In light of climate change and a growing population, water authorities around the world are looking to recycled water.
Community participation is vital to achieve the Sustainable Development Goals. But at the moment it often comes too little, too late.
Urbanisation will require massive amounts of water to sustain the livelihoods of millions expected to move into cities. This may happen at farmers' expense.
There have been modest improvements in water and sanitation provision in Africa, but there is still a long way to go. Most citizens rate their governments’ performance in this sphere poorly.
Climate change is forcing some hard decisions when it comes to water use: energy or food production?