Donald Trump, the 45th president of the United States, has called climate change a “Chinese hoax,” so it’s no wonder climate scientists are freaking out about what will happen to the environment in the years to come.

Trump has already threatened to pull America out of the landmark Paris climate change accord, eliminate the Environmental Protection Agency, repeal environmental regulations, and cut climate funding. He proposed an incoherent energy plan aimed at reviving the coal industry. It’s difficult to know which of these promises Trump will follow through on, but climate scientists warn that his plan is a disaster that would create lasting harm to everything from global biodiversity to food availability.

Possibly the most disastrous move would be preventing the United States from following the Paris agreement, the landmark climate change deal that commits almost every country to reducing greenhouse gas emissions. “We don’t have the luxury of remaining silent because decisions about whether the US is in or outside of Paris climate agreement may affect all of us — they literally affect the kind of world that we’re going to leave behind for future generations,” says climate researcher Benjamin Santer, a member of the National Academy of Sciences. Even if every country keeps its Paris accord promises, we’re still on track for dangerous levels of global warming. And if America does flout its obligations, it’ll seriously hurt international momentum around the issue, especially if other countries follow suit.

The coal industry is not coming back

It would actually take Trump four years to officially withdraw from the accord, but in the meantime he can simply not enforce its guidelines while repealing climate change regulation put in place under the Obama administration, like the Clean Power Plan. With a Republican legislature and a Supreme Court opening waiting to be filled, Trump’s plans will face little resistance.

Trump has also talked about abolishing the EPA, and he’s already picked a climate change skeptic to lead the EPA transition. The abolition or gutting of the EPA could especially hurt people who live in places with high pollution, says Mark Cane, a professor of earth science at Columbia University. For an example of what a country without an EPA looks like, says Santer, look at China: “Look at what a country looks like without rigorous environmental protection, where the population has to endure significant local air pollution that’s responsible for literally tens of thousands of additional deaths.”

Trump’s energy plans are also cause for alarm. He wants to bring back coal mining, he says to restore coal jobs. This is simply not going to happen, says Steven Cohen, director of Columbia University’s Earth Institute. The coal industry is not coming back, for reasons that have nothing to do with climate: natural gas is now far cheaper.

And a push toward coal would “be an enormous step backward with huge health implications,” since coal is responsible for thousands of premature deaths per year, says Kerry Emanuel, a climate scientist at the Massachusetts Institute of Technology. Coal is a dangerous form of energy from start to finish: one way to mine it is by removing the tops of mountains, which destroys ecosystems and groundwater. Coal is also the dirtiest fossil fuel, emitting air pollution and high levels of carbon dioxide. “We can’t be dinosaurs and trying to revive coal is making us dinosaurs,” says Santer. “We can’t imagine that by going back to some time in the past, we solve the problems we’re facing today, that’s not a solution. What happens to dinosaurs? They die out.”

Rising sea levels are a huge threat

The president-elect’s goal of being completely “energy independent” is also ludicrous, adds Cohen. It’s not realistic to be completely self-sustaining in today’s global economy. In fact, being “energy independent” can be risky because if something happens to our refineries, we have no other sources. Not to mention claims that we’re dependent on the Middle East for oil mostly aren’t true. If anyone is dependent, it’s Europe being dependent on Russia, Cohen adds.

If Trump makes good on all his promises, climate change will continue unchecked. There will be staggering losses of biodiversity, more extreme weather events like drought and hurricanes, hotter temperatures, and melting Arctic sea ice. Rising sea levels are one of the most pressing dangers, according to Santer. Sea levels are projected to rise by several feet by the end of the century; that would be devastating for the US East Coast and other places around the world. “Several feet of global sea level rise? That’s a different planet,” says Santer.

For his part, the thing that keeps Emanuel awake at night is the relationship between armed conflict and food and water shortages. “When climate change brings about food and water shortages — which, arguably it’s already doing — that promotes migration pressures that increases the probability of armed conflict,” he says, “which in a nuclear world is a very, very dangerous thing.”

Rampant climate change will affect everything from international trade to food politics. Intense rainfall can lead to flooding and damage to infrastructure and severe droughts, according to Jason Smerdon, a Columbia University climate scientist. Animals aren’t safe, either; climate change has already destroyed so many habitats that researchers speculate that we’re already living through the sixth extinction.

Looking to the future, there are a few ways that the damage could be limited. First, the government is still a system of checks and balances, and even though Republicans will soon control all three branches, there’s a chance someone could object to Trump’s most extreme proposals. Democrats will still have the option of a filibuster. “Donald Trump is not the CEO of the United States and he doesn’t have the power that he’s used to having in his own company,” says Cohen. “So you’re going to see very quickly that if he wants to get anything to happen, there are a whole bunch of stakeholders and a lot of the things that he said he’s going to do he won’t be able to do.”

Though Trump has attacked wind and solar energy, Emanuel, the MIT climate scientist, hopes that Trump may change his tune if he sees the US falling behind economically. “I tend to try to pull the rabbit of optimism out of the black well of despair, and I think that when the president and Congress realize that we are going to be left behind in the transformation of a 6-trillion-per-year global energy market, things will change rapidly,” he says. “The rest of the world understands that we have to innovate clean energy and whoever innovates fastest and best is going to get a strong edge in this colossal energy market.”

And even if Trump has his way, that global growth in clean energy will continue. Emanuel hopes the election will shake up the international community and make them see that they can no longer look to the United States for leadership in this area. “Renewables are here to stay and they are already employing millions of Americans and that’s going to continue irrespective of decisions made by the Trump administration,” says Santer, the National Academy of Sciences climate researcher. “Now they can either make it easier for the rise of renewables and for a transition to a low-carbon energy future, or this administration can make that much more difficult.”