Sumatran tigers are running out of places to live. Their population fell by 16.6 per cent between 2000 and 2012, and the remaining tigers are trapped in shrinking forests.

“We’re really at a tipping point in terms of how much habitat is left that tigers need for their long-term survival,” says at Nanyang Technological University in Singapore.

The Sumatran tiger () is a subspecies of tiger, only found on the Indonesian island of Sumatra. It is critically endangered, due to poaching, the expanding oil palm industry and rampant deforestation.

Luskin and his colleagues spent a year tracking tigers through Sumatran forests, using cameras to track each individual animal. They combined their data with other scientists’ results, allowing them to accurately estimate how many Sumatran tigers are left.

Not enough females

They focused on the number of females able to reproduce, which is a crucial indicator of the tigers’ long-term chances. Conservationists tend to focus on protecting populations that have at least 25 breeding females, to avoid inbreeding.

Luskin’s team found that there are now only two habitats with viable populations, down from the 12 thought to have existed 70 years ago. Gunung Leuser in the north and Kerinci Seblat farther south have 48 and 42 breeding females respectively.

The researchers say the population decline is driven by the rapid loss of the tigers’ habitat. Indonesia has the fastest deforestation rate of any country: it lost 60,000 square kilometres (37 per cent) of its primary forest between 2000 and 2012. During that period, 16.5 per cent of tiger-occupied forest vanished.

Out of the frying pan

Tigers are already extinct on Java, Bali and Singapore. But in the last 20 years there has been a concerted effort to protect Indonesia’s last tiger population from extinction.

On one measure, this effort has succeeded. The team found that the density of tiger populations – the number of tigers per square kilometre – has gone up, rising 4.9 per cent annually between 2000 and 2012. Tiger densities were 47 per cent higher in untouched forests, compared to logged forests. “Loggers make roads into the forest, and that makes it easier for poachers to get in and get the tiger out,” says Luskin.

The problem is, says Luskin, “while anti-poaching efforts have been successful, at the same time so much forest has been lost that it’s offset those commendable conservation gains.”

It doesn’t help that Sumatran tigers need larger home ranges than their Indian counterparts. Each tiger needs roughly 240 square kilometres, seven times the size of Manhattan Island. That makes them sensitive to habitat loss. “Each additional hectare lost has a disproportionate impact on the tigers,” says Luskin.

It is critical to protect the two sites with viable populations, says at the Wildlife Conservation Society in Bronx, New York. The tigers there could ultimately restore the populations elsewhere on the island. “This is a very clear call to arms,” he says.

Read more: Trade in tiger parts unrelenting in Sumatra

To build or not to build

In July 2012 India experienced the largest power outage in history. More than 620 million people were left without electricity after a transmission line in the northern part of the country failed, buckling under too much electrical load. Nearby power lines that took up the slack also failed, and lights across 22 Indian states went out.

All power grids are at risk of this rare domino effect, called a cascading failure, and pinpointing which parts of the grid are most vulnerable could prevent future costly blackouts.

at Northwestern University in Evanston, Illinois and colleagues modelled this risk in the North American power grid. Surprisingly, they found that only 10.8 per cent of all links in the US and southern Canada were at risk of failing in a cascade event.

Their model incorporated data from the Federal Energy Regulatory Commission between 2008 to 2013, and accounted for factors like changing seasons and power demand levels. Nishikawa says more vulnerable links are located near densely populated cities, where there are a greater number of power lines that are connected to each other.

Building redundancy

“With almost 100,000 lines considered, this is��the largest study of cascading failures I have seen so far,” says at Jacobs University in Bremen, Germany. Kettemann says that this simulation goes beyond previous studies in that it incorporates how quickly these power lines heat up and fail.

Power grids protect against failures by building redundant paths – if a line is damaged by wildfires or falling trees another can take over – but cascading failures take out these redundancies too. When the failed line’s power is rerouted to another line, that line can also become overloaded and fail.

Unlike when Puerto Rico’s electrical grid went down because of damage from Hurricanes Irma and Maria, cascading failures happen because of what’s happening inside the grid. Initial failures that are close together are more likely to lead to larger cascades, Nishikawa says.

Utility companies can now prioritise the upgrade and maintenance of those weak links with the highest frequency of past failures, he says. Identifying which lines are most vulnerable presents a cost-effective way of preventing future cascades and improving grid resilience.

Nishikawa also hopes that the analysis can inform changes in how power is routed through existing lines, so less electricity is flowing through those at higher risk.

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In the last four years the Arabian Sea has experienced unprecedented storms, and a new study reveals that climate change has made such events more likely to strike.

The Arabian Sea sits between Yemen, Oman and India. Cyclones are rare there – yet in 2014, caused flash-floods in north-east Oman, killing four people. A year later, two cyclones hit back-to-back for the first time. Chapala and both made landfall in Yemen as “extremely severe cyclonic storms” – with winds as strong as hurricanes – killing 26 people and displacing tens of thousands.

These events puzzled at Princeton University in New Jersey. He says storms this severe typically occur in spring, months before the monsoons. Yet the three deadly cyclones all hit in October and November, late in the monsoon season.

Wondering if climate change might be changing cyclone behavior, Murakami and his colleagues used a sophisticated climate model to compare conditions in 2015 to conditions in 1860, when humanity’s carbon footprint was much smaller. They found that, in 2015, 64 per cent of the increased hurricane risk in the Arabian Sea was down to climate change.

“We’re seeing that human activity affects not only climate, but shorter events like rainfall and cyclones,” says Murakami.

“These results are striking and add to the large volume of information connecting human activities to tropical cyclone behavior,” says at the National Oceanic and Atmospheric Administration. He says the Arabian Sea is at particular risk, because many people live nearby and cyclones there have nowhere to go except land.

Reaping what we sow

Similar changes to storms are taking place in the Atlantic and Pacific oceans.��, then at the Weizmann Institute of Science in Rehovot, Israel and her colleague studied extra-tropical storms – which form a long way from the equator. These storms produce anything from mild showers to thunderstorms, blizzards and heavy gales.

They tracked the births and paths of hundreds of such storms and found that they are shifting towards the poles: further south in the Southern Hemisphere and farther north in the Northern Hemisphere. Not only are they forming further from the equator, they are covering greater distances. That means they are creeping closer to continents like Europe.

Researchers have also found that more hurricanes could reach Europe in the future, and that the west coast of the United States and the UK may see more extra-tropical storms.

Read more: We all get poorer every time a climate disaster strikes

A noticeable jump