It is easy enough to say that we need randomized controlled trials in conservation, but how would you actually design such a study? Here is an example,
Ferraro, P.J., R. Godoy, D. Karlan, W. Leonard, and D. Wilkie. 2002. Field Experiment To Assess The Effects Of Performance Payments On Ecosystem Conservation, Quality Of Life, And Territorial Rights of Indigenous Populations: A Proposal.