Farmers aren’t guaranteed a good cacao crop each year. Farms tend to grow only a few varieties of cacao. That means the plants lack genetic diversity—the variety of genes (units of hereditary material) within a species. Because most cacao plants grown today share the same genes, they’re vulnerable to the same diseases. Unfortunately, many farmers either don’t have access to or can’t afford the pesticides and fungicides that kill disease-carrying pests and harmful fungi.
Hotter temperatures and extreme weather patterns brought on by climate change compound these problems, says Ethan Budiansky, the director for environment at the World Cocoa Foundation in Washington, D.C. “Cacao trees like heat, but not too much, and they require sufficient rain,” he says. “As the climate becomes less hospitable, there’s less land that’s suitable for growing these plants.”