Trees fight to grow as high as possible to catch sufficient sunlight. This sometimes requires them to sacrifice root depth to extend their presences above ground as much as possible. But the downside of this upward push is that it can make them easier to push over, as was the case with the tree we saw, which had a weak and shallow root system.

Among the countless killers with leaves are "stranglers" like banyan figs. Birds drop their seeds onto tree branches, where they grow roots downward along the trunks and gradually choke their hosts, stealing their nutrients and light until they die of deprivation.

"It's harsh," Chen said. "Many trees have their own ways to fight back, just like we humans struggle greatly to make a living."