To modern man, is unspoiled nature a place of freedom or a jail cell? This could be looked at through the lens of the films "Into the Wild," "Wild," and "Castaway," as well as the Romantic Period--which brought naturalism into the methodology and content of literature.
The giant trash gyers in the ocean....what can be done to recycle them or utilize them? What can be done to keep them from growing? I've read of ambitious ideas for cleanup and even islands created from them.
Research the history of creating underwater conservatories and "National Parks." Clinton, specifically, is to thank for Hawaii's enormous conservatory.
Is nature inherently good, evil, or indifferent?
The planet's strangest animals.
Animals who have made a comeback and are off of the endangered species list, or were almost extinct, but now have healthy populations. A more positive take on environmentalism.
What is more important, putting resources towards helping humans or protecting the environment? Or, are we so dependent that they are one and the same.
Animals that break the rules: fish that breathe air, animals that freeze and thaw out, gender changing or unisex animals, color changing animals, cannibalistic animals (black widow spider) ect.
Fastest animals on the planet.
The ethical and environment affects of zoos and animal parks.
Is it the government's job to preserve natural spaces or should it be privatized?
Should National, State, and local parks be forced to provide accessibility? Have places like Yosemite and the Grand Canyon become so accessible that they are no longer "wild." Should citizens gain free entry to these places because of tax revenue?
The West Coast drought: How bad is it? Will this year change it? What can we do to cut back on water usage? Is there a way to store water without disrupting delicate wildlife? In the past decade, dams have been torn down and new reservoirs not built because of salmon spawning being affected by not having a natural and clear path between the inland rivers and the ocean.
Species that are unique to a region and found nowhere else in the world.
I hope these ideas sparked something for you, or at least amused you. Good Luck!