Arriving home after the hurricane, you find the roof partially collapsed, the front door ajar, and the front window out. Inside, belongings are scattered, some missing altogether. What's gone? What do you need to do to rebuild? It occurs to you that the household inventory you made last year will come in handy in restoring your home.

Our collective home, the Earth, faces just this scenario. Not from a local hurricane, or even a single global catastrophe. Instead a creeping catastrophe has overtaken us, and we are witnessing the loss of much of our global inventory of plants and animals that are part of the intricate ecological balance that we depend upon for human survival.

Elizabeth Kolbert, the Pulitzer Prize-winning author who speaks at the Academy of Natural Sciences of Drexel University on Wednesday, calls this the "sixth extinction." Her book The Sixth Extinction: An Unnatural History, outlines a dozen case studies of how species worldwide - from coral reefs to rainforests to deserts - are dying off at an alarming rate. In recognition of her contributions to interpreting natural science, the academy will award Kolbert the Richard Hopper Day Memorial Medal.

Now, you may be looking out your window and thinking that the trees and flowers, squirrels and deer, everything seems more or less OK. But scientists, whose business is keeping track of biodiversity, have seen alarming changes in just a few decades - slow at first but now accelerating. The previous mass extinctions, called the Big Five by paleontologists, occurred intermittently during the past 450 million years and were periods during which millions of the species alive at the time became extinct. Humans played no role in these die-offs. And even if humans were around, we could not have done much to avert the Big Five.

Long-term changes in climate and ecosystems, inexorable movements of the massive crustal plates that spurred volcanoes, built mountains, and repositioned land masses and oceans, and the occasional impact of a large asteroid, all played a role in the Big Five that paleontologists are still doing the forensic research on. The millions of death certificates for Earth's species would list "natural causes" as the reason for their demise. But the sixth extinction is different - its rapid onset and broad scope appears to have been caused by a single species. Us.

We have quickly altered the planet and its atmosphere in ways that make it unlivable for many of the species we admire and depend upon. The effects of human-caused climate change extend way beyond the direct damage of human structures and society. The sixth extinction is the very ugly face of climate change being visited upon our fellow species on this planet.

But back to that inventory. How do we know something is missing from our global accounting of species? As it turns out, due to the activities of 18th-, 19th-, and 20th-century scientists, we have a huge inventory with preserved samples to use to figure out what's missing. The Academy of Natural Sciences is one of those places where data and samples are preserved, with more than 18 million specimens of plants, shells, insects, birds, fish, fossils, and other organisms that have been preserved, studied, and kept safe for centuries. Along with collections at other museums, these precious specimens - identified to species, with data on where they lived and when - provide an album of snapshots of life on Earth.

At the academy and other museums around the world, a major effort is under way to put this collection data online in a way that land managers and scientists can use to address potential threats to species survival and ways of restoring lost species. This kind of information is essential if we are to devise ways of slowing species loss, or if not that, at least understanding what we've lost and how to cope with that loss and maintain ecosystems that all life depends on.

The scientists who long ago collected such specimens had no idea they were taking stock of a natural world that would someday change rapidly before our very eyes. But luckily, they did preserve that inventory, and we keep their collections in trust. Let's hope we keep that trust for future generations who may be dealing with the aftermath of a devastating loss in global biodiversity.

Rick McCourt ( and Ted Daeschler ( are curators at the Academy of Natural Sciences and professors in the Department of Biodiversity, Earth and Environmental Science at Drexel University. Daeschler is also the academy's vice president for collections and the library.