India, Sept. 14 -- S ome wildebeest don't migrate any more. Forced to stay put, their absence has caused wildfires, altered landscapes, even resulted in a higher incidence of giraffe-calf death. As tourism numbers rise and economies grow, roads, railways, oil and gas pipelines, housing, and fences to protect agriculture and livestock are blocking historical routes. This has forced most of Africa's scattered wildebeest herds to alter, shrink or give up their migrations. "There used to be dozens of long-distance migrations of this species all over the continent until the turn of the century," says Derek Lee, principal scientist with the US-based research and conservation group Wild Nature Institute. "Only three populations continue to migrate...