Question

Which issue has led to conflict between developing nations and environmentalists?

Answer 1

There are tons of issues. You'll have to be more specific.

Answer 2

developing nations exploit natural resources more deliberately than developed nations. why? Developing nations are great at producing things for the mass market, because in developing countries wages are low, governments are flexible, tax rates are lower. so, as industries are the main features of developing countries' economy, they naturally exploit natural resources more, for example: Carbon dioxide and other Clorofluoro carbon emission, water toxicity, and air pollution. so environmentalists always have a conflict with developing nations.
but again, there are tons of issues like this as jim says.