According to a campaign recently advertized on television, tropical rainforests are shrinking at an alarming rate. I know the perfect way to save them. Make them nuclear waste dumps. Tropical ecosystems are very robust given the enormous variety of species inhabiting them and the rapid rate of growth and reproduction in them. I'm pretty sure one could even sprinkle every single bit of the world's high-level nuclear waste all over any rainforest and barely cause any ecological harm in the long term. But even when properly encased and buried under hundreds of meters of bedrock, nuclear waste would surely repel superstitious humans.
Don't believe me? Just read about how wildlife thrives in the Chernobyl area (not even a tropical rainforest).