POTUS didn't waste any time. Just hours after he was sworn in as the nation's 46th president, Joe Biden began rolling back some of Donald Trump's most contested policies.

Associated Press reports Biden signed a total of 17 executive actions—15 of which were orders—that cover everything from climate change and the U.S.-Mexico border wall to the coronavirus pandemic and the Muslim ban. The AP points out that only two other modern-day presidents have signed executive actions during their first day in office, and each of them only signed one. 

"We're not going to wait weeks. We're going to come in and hit the ground running," Cedric Richmond, the incoming director of the White House Office of Public Engagement, said in an interview. "I think that that is the most important part, to show the American people that we're serious about governing."

Among the key actions Biden signed on Wednesday was an order to rejoin the Paris climate accord. The Trump administration officially pulled out of the agreement just a day after the 2020 presidential election, making the U.S. the first country to withdraw from the international climate change treaty. It'll reportedly take 30 days for the country to formally re-enter the agreement.

Environmentalists also praised Biden for signing an action that revoked a presidential permit for the proposed Keystone XL pipeline, as well as an order to review the Trump administration's rollback of environmental protections.

"The window for meaningful action is now very narrow – we have no time to waste," Dr. M. Sanjayan, chief executive of Conservation International, told NPR. "President Biden's action today is certainly a step in the right direction."

POTUS also implemented a national mask mandate on all federal property, and committed to re-engaging with the World Health Organization. Trump cut ties with WHO over the summer, claiming it had mislead the world about the global pandemic. Dr. Anthony Fauci, the nation's leading infections disease expert, is expected to represent the U.S. at WHO's executive meeting Thursday.

Another one of Biden's key actions was the termination of the so-called "Muslim travel ban," which prohibited people from seven countries—most of which were predominantly Muslim—from entering the U.S. He also halted construction of the U.S-Mexico border wall by ending Trump's national emergency declaration that diverted funds to the project.

In addition to introducing a sweeping immigration reform bill, Biden called on lawmakers to strengthen the Deferred Action for Childhood Arrivals (DACA) program, which aims to protect undocumented immigrants who entered the U.S. as children. Trump made several efforts to terminate the Obama-era program, but the Supreme Court ultimately blocked his administration from doing so.

Biden also directed the Department of Education to extend the pause on student loan payments until Sept. 30 at 0% interest. The pause on federal student loan payments, which was enacted due to the pandemic, was set to expire at the end of this month. In addition to student loan payments, Biden extended the federal ban on evictions until the end of March, CNBC reports.

"Over the centuries through storm and strife, in peace and in war, we have come so far," Biden said during his inauguration speech Wednesday. "But we still have far to go. We will press forward with speed and urgency, for we have much to do in this winter of peril and possibility. Much to repair. Much to restore. Much to heal. Much to build. And much to gain."