A version of this post originally appeared on Devex.com.

Since the very first Earth Day nearly five decades ago, the environmental movement has tackled a wide range of problems, including air pollution, water contamination, deforestation, and biodiversity loss. But this Earth Day, there are two fundamental issues the movement must address over the coming decade if it is ever to defuse the tension between human development and the environment. In fact, these two issues underlie many, if not most, of the world's environmental challenges.

I'm referring to the human quest for food and the human quest for fuel.  

The food system has significant — but often underappreciated — impacts on the environment as my colleagues and I show in our report, "Creating a Sustainable Food Future." Take climate.  

Nearly a quarter of the world's annual greenhouse gas emissions are linked to agriculture. About 14% come from livestock, fertilizer use, rice production, and farm-related energy consumption. Another 10% results from the clearing of forests, primarily for agriculture. Such conversion of natural ecosystems into farms and pastures is the number one cause of forest and biodiversity loss.

Take water. Agriculture is responsible for approximately 70% of the world's freshwater withdrawals and has a major impact on water quality. For instance, fertilizer runoff from farm fields plays a major role in creating the massive annual "dead zones" in lakes and coastal waters such as the Chesapeake Bay and Gulf of Mexico. Next time you hear about a water shortage somewhere, ask what role unsustainable water use for food production played in the crisis.

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