Stortroen, an 82-year-old retired insurance claim center manager from St. Paul, Minn., has joined research outings in places ranging from Australia to South Africa. This was his first time assisting scientists in the Mojave Desert.

"I enjoy the teamwork. I enjoy working with nature," he said, pausing beside boulders while the group took a break and pulled out their water bottles.

Stortroen was one of 15 Earthwatch volunteers — American, British and Canadian — who helped with the research earlier this month in Joshua Tree National Park. The volunteers split up with park biologists and UC scientists to conduct surveys of plants, count birds and record the numbers of lizards and other reptiles.