The United Nations warned that continued fossil fuel use is causing 1.5degC global warming relative to 1850-1900 levels. This threshold will lead to “unprecedented” severe weather events. New research has shown that climate change will cause coral bleaching, which will be catastrophic for the reefs and possibly the marine life around them.

Bleaching can be caused by changes in ocean temperature, pollution, sunlight overexposure, and low tides. All of these factors can cause coral to become stressed and release the algae in its tissues. Corals become more susceptible to diseases when they lose their primary food source of algae.

According to the Environmental Protection Agency, reefs are “among most biodiversity and valuable ecosystems of Earth”. They provide a vital resource for 25% of marine life. About half a million people also depend upon reefs for their food, coastal protection and income. Researchers warned that climate change will continue to impact the planet’s ecosystems and will “overwhelm” them. This will lead to a dire situation for almost all of them.

PLOS Climate published a new study on Tuesday that focused on thermal refugia. These are areas that can sustain coral reefs at the right temperature, even when nearby ocean temperatures rise. Currently, 84% of coral reefs are thermal refugia, meaning they have had sufficient time to recover from heat waves that can bleach and kill coral reefs.

Researchers found that only 0.2% of Earth’s thermal refugia will be able to recover from extreme heat events. More than 90% of these reefs will also experience “an intolerable degree of thermal stress” once the planet reaches 1.5degC. Researchers found that no thermal refugia are left at 2degC and all coral reefs will become vulnerable.

The study was published on the same day as other scientists who concluded that marine heat is now the “new normal”.

Researchers believe that the only areas that could survive 1.5degC are the Coral Triangle and small regions of Polynesia, which have lower temperatures. Even those areas would not be suitable if the Earth experiences 2degC warming.

Adele Dixon, lead author of the study, stated in a statement that “our finding reinforces and confirms the stark reality of global warming’s effect on coral reefs.”

The world could be just a few years away as this unfolds.

In August, the U.N.’s Intergovernmental Panel on Climate Change said that the world would likely reach 1.5degC warming by 2030. According to the IPCC, 1.5degC global warming will lead to more extreme heat events and greater frequency. Coral reefs usually take around a decade for them to recover and function again after severe coral bleaching events. However, under the forecast climate scenarios they won’t have enough time.

Global warming is a result of human activities such as excessive deforestation, overuse, and burning fossil fuels.

Researchers suggested some ways to save the reefs from deterioration, such as removing tourism and fishing, and allowing coral to migrate to better environments. However, they cautioned that these measures might not be effective in the long-term and that global warming must be addressed quickly.

Scott Heron, a physics professor at ARC Centre of Excellence for Coral Reef Studies, Australia, stated that the study confirmed that people need to take urgent action on greenhouse gas emissions.

While the Paris Climate Agreement contains the majority of countries committed to keeping below 1.5degC, researchers from this study stated that it is not enough to save coral reefs.

Maria Beger, research supervisor, stated that coral reefs are vital for marine life and more than half a million people whose livelihoods depend on them. If we want our children to have a reef habit, we must not only meet the Paris goals, but also exceed them.