We're in the midst of a biodiversity crisis. For those of us in the North, that can seem abstract; for the rural poor in the  developing world, it's all too real. Their absolute dependence on the bounty of forests, deserts and coasts means 'biodiversity loss' can mean losing all: food, fuel, building material, medicine, forage, livelihoods and culture. The good news is that it can work the other way. Poor communities, as long-term stewards of the South's natural riches, are steeped in profound knowledge about them. As this pocketbook shows, working with them can reverse the downward spiral of environmental degradation. By banking on biodiversity, we can protect our natural legacy while tackling poverty locally, nationally and globally.