In the Western Ghats, the forests kept for the gods are raising the next generation of trees

In Vanzole, a village in India's Western Ghats, ecologist Omkar Pai and two local guides measured the giant trees that grow in forests set aside for village deities. Under those trees, young forest was growing at rates the surrounding village land could not match.

In Maharashtra these groves are called devrai. They are patches of forest that belong to a local deity, and by tradition no one cuts their trees or takes their wood. Pai, first author of a study by the Pune-based Applied Environmental Research Foundation (AERF), wanted to know what that protection means for the forest itself. The answer was in the ground at the foot of the trees.

Sacred groves held nearly twice as many giant-tree species as the village land around them. Beneath the grove trees, the next generation was taking root. 91 percent of fishtail palm saplings grew under grove trees, compared with 47 percent under village trees. This is the palm that villagers in the region tap for sap to make toddy and jaggery. The contrast was sharper still for Strychnos nux-vomica, known locally as kuchla, whose seeds are traded for pharmaceutical and Ayurvedic use. Saplings grew near 77 percent of the grove trees and near only 5 percent of the trees in the village.

Kevin Matteson of Project Dragonfly at Miami University in Ohio, a co-researcher on the study, calls the giant trees "ecological catcher's mitts." Their crowns draw in hornbills. The Western Ghats are home to the great hornbill, whose wings span about one and a half metres, and to the Malabar grey hornbill, which lives nowhere else. These birds swallow large fruits and can carry the seeds in their gut for hours before dropping them kilometres from the parent tree. A giant tree in a grove is a place where forest seeds arrive, and also the point from which they are carried out across the landscape.

For Pai, the people who know these forests matter as much as the trees. Local knowledge holders, he says, "actually map the memory" of the forest. They know which trees are old and which groves have been left alone, and they know where a guide should lead a scientist.

That memory is now under pressure from an unexpected direction. The study warns that as villages replace traditional forest shrines with concrete temples, the nursery is lost. Roots are disturbed during construction and the undergrowth is cleared, and the saplings are cleared with it. The shrine keeps its deity, but the forest around it stops growing back.

The botanists Madhav Gadgil and V.D. Vartak surveyed Maharashtra's sacred groves in the 1970s and argued for their continued protection. In Vanzole, the evidence for that argument is growing at the foot of the oldest trees.