A graphical representation of the size of the asteroid thought to have killed the dinosaurs, and the crater it created, compared to an asteroid thought to have hit the Earth... Picture this: A massive asteroid almost as wide as Rhode Island and about three to five times larger than the rock thought to have wiped out the dinosaurs slams into Earth. The collision punches a crater into the planet's crust that's nearly 500 kilometers (about 300 miles) across: greater than the distance from Washington, D.C. to New York City, and up to two and a half times larger in diameter than the hole formed by the dinosaur-killing asteroid. Seismic waves bigger than any recorded earthquakes shake the planet for about half an hour at any one location – about six times longer than the huge earthquake that struck Japan three years ago. The impact also sets off tsunamis many times deeper than the one that followed the Japanese quake.

Logistics were extremely challenging because Liberia's infrastructure was almost completely destroyed during the civil war and because of the remoteness of some of the survey locations. When Liberia enters the news it is usually in the context of civil war, economic crisis, poverty or a disease outbreak such as the recent emergence of Ebola in West Africa. Liberia's status as a biodiversity hotspot and the fact that it is home to some of the last viable and threatened wildlife populations in West Africa has received little media attention in the past. This is partly because the many years of violent conflict in Liberia, from 1989 to 1997 and from 2002 to 2003, thwarted efforts of biologists to conduct biological surveys. An international research team, including scientists of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, has now counted chimpanzees and other large mammals living in Liberia. The census revealed that this country is home to 7000 chimpanzees and therefore to the second largest population of the Western subspecies of chimpanzees. As Liberia has released large areas for deforestation, the local decision-makers can now use the results of this study in order to protect the chimpanzees more effectively.