From the Living Planet Report 2012:
Biodiversity continues to show a downward trend, especially in tropical areas and freshwater habitats.
• Across the globe, vertebrate populations were on average one-third smaller in 2008 than they were in 1970.
• Freshwater species declined more than for any other biome—37 percent between 1970 and 2008.
• Freshwater species in the tropics declined by a much greater extent—70 percent. This is greater than any species decline measured on land or in our oceans.