The Recent Mass Animal Deaths, Mapped

There is now a Google map of the recent "mass animal deaths." There are 30 of these events listed on the map in total, including "hundreds" of dead starfish in South Carolina, 70 dead bats in Arizona, and, of course the falling birds of Arkansas and Louisiana. There are also a few European and Asian events logged.

Most of the events listed are recent ones, which unfortunately doesn't really help put the past week's events in context. What we need is a much broader perspective.

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How many mass deaths are there each year? Has that number been increasing or decreasing over the past few decades? How many are caused by human activity? How many have the same cause (like unusually cold water, for example, which might be an effect of climate change)?

And what counts as a mass death, anyway? Is "several dead manatees" a sign of impending environmental collapse or just an unavoidable—if unfortunate—fact of manatee life?