With Antonin Scalia gone from the Supreme Court, there will be only eight justices until his replacement is nominated and confirmed. If the court splits 4-4 over a decision, the lower court ruling will be upheld without new precedent being set.
Scalia wasn’t completely anti-environment but he did effectively weaken several important environmental protections during his term. His absence makes it less likely that Pres. Obama’s Clean Power Plan will be aggressively challenged.