From the RePEc blog is a discussion of their lists of heavily cited papers. The #1 cited "recent" (i.e., last five years) environmental economics paper comes in at #17:
Carson, Richard T. & Hanemann, W. Michael, 2006. "Contingent Valuation," Handbook of Environmental Economics, in: K. G. Mäler & J. R. Vincent (ed.), Handbook of Environmental Economics, edition 1, volume 2, chapter 17, pages 821-936 Elsevier.
This paper offers an incredibly detailed survey of the junk science that is the contingent valuation method (i.e., ask a hypothetical question, get a hypothetical answer ... but with a lot of bonuses!). Read closely for references to papers by those lovable bloggers, Haab and Whitehead. Carson and Hanemann is at #369 on the all-time citation list (the top 1% of all RePEc papers) and tied with:
Grossman, Gene M & Krueger, Alan B, 1995. "Economic Growth and the Environment," The Quarterly Journal of Economics, MIT Press, vol. 110(2), pages 353-77, May.
Grossman and Krueger is the famous Kuznets Curve paper:
We find no evidence that environmental quality deteriorates steadily with economic growth. Rather, for most indicators, economic growth brings an initial phase of deterioration followed by a subsequent phase of improvement.