Declines in amphibian and reptile populations have been a global issue, with more than one third of all species globally threatened. At La Selva Biological Station in Costa Rica, researchers have shown that over 75% of all species of terrestrial amphibians have declined by 75% since 1870. This is among the most critical issues in conservation biology, and researchers at La Selva want to know why the sudden loss of species has occurred. These enigmatic declines have been particularly problematic in Central and South America without a clear indication of the cause. Population declines in montane regions have been associated with climate-induced outbreaks in chytridiomycosis, an infectious disease caused by a fungus, but this is not the case for the southern species.
A recent study by Whitefield and colleagues at La Selva, published in 2007, shows a strong correlation between species declines and climate-driven reductions in the quantity of standing leaf litter. This is a critical micro-habitat for the species and any significant habitat loss would directly impact the population. This study has sampled species since the 1950s and includes about 26 species of frogs, 27 snakes and 2 types of salamanders. The majority of the La Selva reserve consists of old-growth forest and a small percentage contains abandoned cacao plantations with secondary succession regrowth. Sampling litter plots involves the demarcation of an area of the forest floor followed by a thorough search for all amphibians and reptiles.