Since the very first Earth Day  more than four decades ago, the environmental movement has tackled a wide range of problems, including air pollution, contaminated water, deforestation , biodiversity loss, and more. But this Earth Day, I propose that there are two fundamental issues the movement must address over the coming decade if it is ever to defuse the tension between development and the environment. In fact, these two issues underlie many, if not most, of the world’s environmental challenges.
I’m referring here to the human quest for food  and the human quest for fuel.
Unsustainable Food Production
Food production has significant―but often underestimated―impacts on the environment. Take climate, for instance: About one-quarter  of the world’s annual greenhouse gas emissions are agriculture-related. In particular, nearly 13 percent  of global emissions comes from livestock, fertilizer use, and farm-related energy consumption, while another 11 percent  results from the clearing of forests and other ecosystems, primarily for agriculture. Take water : Agriculture is responsible for approximately 70 percent  of the world’s freshwater withdrawals and up to 85 percent  of its freshwater consumption. Farming also impacts water quality; excess fertilizer washes from farm fields into waterways, creating massive “dead zones”  in lakes and coastal waters.
Or take land: Today, nearly 50 percent  of the planet’s land mass outside of deserts and permanent ice is used for growing food. Next time you take a flight, look out the window. Most of what you will see isn’t cities and concrete; it’s farms and pastures.
And then there are the oceans. Fishing now occurs across one-third of the world’s marine surface, and unsustainable fishing threatens 60 percent  of the world’s coral reefs.
The Environmental Costs of Fuel
The human quest for fuel―or energy―has similar, wide-scale impacts. Take climate, once again: About two-thirds  of global greenhouse gas emissions arise from burning coal, oil, and natural gas for power, heat, and mobility.
Take air pollution: Burning coal is a major source of sulfur dioxide, nitrogen oxide, particulate matter, and mercury emissions, which are implicated in smog, acid rain, and various human health problems. And recent events in Beijing —where residents inhale life-threatening pollutants—remind us that urban air pollution woes are far from over.
Our Mission, Should We Choose to Accept It
Of course, all of this doesn’t mean we should forgo food and fuel. We all need to eat; we all need energy to improve our lives. And food and fuel are critical for the global economy. Although it directly accounts for just 3 percent of global GDP, agriculture employs more than 2 billion people . That’s more than one-quarter of the human population. Likewise, the energy sector is a large direct and indirect employer around the world.
If the aspirations of Earth Day are ever to be realized, then figuring out how to implement sustainable agriculture  and deploy sustainable energy at scale will need to be a strong focus of the environmental movement. Such a focus would directly tackle the underlying causes of most of the world’s environmental challenges. It would ensure environmentalism aligns with human development—little is more basic to human well-being than food and energy. And such a focus would be relevant for all nations—every country is concerned about its food and energy security.
So it boils down to food and fuel. Fix these, and much of the rest may fall into place.