Tomorrow is Earth Day, which some Americans will mark by celebrating conservation successes – and others by pointing out what’s still to be done. The Conversation is noting this day of environmental awareness by taking a closer look at challenges spanning from the deep oceans to the stratosphere.

Since taking office last year, the Trump administration has moved to eliminate or narrow many environmental regulations. Amanda Rodewald of the Cornell Lab of Ornithology spotlights one example: protection for migratory birds.

Looking to the future, University of California, Irvine Earth scientist Keith Moore explains how prolonged warming of the oceans could change the distribution of tiny phytoplankton, with impacts rippling up marine food chains.

Ecologists Sujay Kaushal, Gene Likens, Michael Pace and Ryan Utz describe how they identified an emerging water pollution problem: increasingly salty U.S. rivers.

And Colorado State University atmospheric scientist A.R. “Ravi” Ravishankara offers some good news. A treaty signed in the mid-1980s has reduced the use of chemicals that deplete Earth’s protective ozone layer, which is on the road to recovery.