It’s that time again. Earth Overshoot Day is here and the clock continues to tick. As I described in Foreign Affairs last year, Earth Overshoot Day is the date on which humanity’s demand for natural resources exceeds the earth’s ability to renew them in a year. Last year, we hit that mark on August 20. This year, it comes one day earlier. For the remainder of 2014, in other words, we will be living beyond our planet’s means, spending more than it can afford -- the equivalent of a farmer eating both the crops grown this year and the seeds for next.

Earth Overshoot Day is calculated by scientists and data crunchers at Global Footprint Network, an independent think tank based in the United States, Switzerland, and Belgium. They use two data points: the earth’s current biocapacity (the area of land and water available to produce renewable resources and absorb CO2 emissions) and the world’s ecological footprint (the area of land and water required to meet humanity’s demand for natural resources). The calculation is an approximation, but the picture it paints is undeniable. The planet simply cannot produce the amount of resources people demand, and we demand more every year.

The challenge requires action from all corners of society. Over the past decade, many of the world’s biggest companies -- Coca-Cola, Mars, and Unilever, to name a few -- joined World Wildlife Fund, of which I am president and CEO, and other NGOs to help reduce their ecological (and, in many cases, financial) costs. They understand what is at stake for their businesses and their bottom lines. To thrive, companies need healthy communities, public goodwill, and, most important, a dependable supply of resources. By aggressively pursuing sustainability, actors in the private sector are ensuring their own future.

Just as corporate self-interest can push companies toward sustainability, national security concerns can push governments in the same direction. Within the U.S. government, leaders from the defense, intelligence, and diplomatic communities have started regularly delving into scarcity issues, most often because of emerging threats to national security. For centuries, societies have risen and fallen on their ability to sustainably harness what nature provides. And the stakes are even higher today as demands on the planet grow.

Already, increasing scarcity -- especially related to fresh water -- is stressing governments’ ability to provide food and energy to their citizens. Particularly in rural areas, scarcity pushes tens of millions of inhabitants to urban areas. Many governments are simply unable to respond to the needs of citizens in the new mega cities; they seldom discuss the difficult trade-offs among water, food, energy, and growth, simply hoping that development will solve all the problems. And the problems don’t stop at the border: regional cooperation organizations are often unable to address tensions among neighboring countries vying for scarce resources, such as timber, water, and energy.

The United States can take either a proactive or reactive approach to the emerging crisis. It can support smart management and conservation of natural resources to avert crises, or it can deal with conflicts or wars that have already broken out. Proactivity might seem like a tall order. But in the international arena, there are several good examples of it. For instance, the United Nations Watercourses Convention officially went into effect on August 17. The convention establishes basic standards and rules for cooperation between users of trans-boundary waters and provides the first global framework for legal protection against future human and environmental threats between watercourse states.

No resource is more valuable to humans than freshwater. Beyond basic human needs, water also goes into every single product manufactured today. Water shortages already affect two billion people in more than 40 countries. The inevitable consequence? Conflict. The World Resources Institute’s Aqueduct tool is a telling indicator. It maps water risk around the globe, and it is no coincidence that the regions with the highest overall water risk have a history of conflict and instability.

Take Syria, for example. There are myriad reasons for the country’s ongoing civil war, but lack of water resources due to the overuse of the Euphrates River among Iraq, Syria, and Turkey certainly added strain to an already tense situation. A devastating drought in 2006 forced an estimated 1.5 million Syrians to relocate. Nearly 75 percent of Syria’s farmers suffered total crop failure and subsequently moved to cities looking for work. Less water, less food, fewer jobs, and a million more people in densely packed neighborhoods -- this was lighter fluid on existing kindling.

Syria is an extreme example, but there are thousands of others. Another looming conflict is along the Mekong River between Cambodia and Laos, where a massive dam is slated for construction starting this year. The dam is meant to create energy for export primarily to Thailand and Cambodia, but it will jeopardize the critically endangered Irrawaddy dolphin and the livelihoods of 60 million people living in the Lower Mekong Basin, who depend on the area’s inland fisheries -- some of the world’s most productive -- for work. The economic damages will mostly come on the Cambodian side of the river, but Cambodia is powerless to stop construction. Because neither Cambodia nor Laos have ratified the Watercourses Convention, there is little the international community can do.

That is why, although no one pretends that the convention is a final solution to all water issues, the world must continue to push as many countries as possible to ratify it. It will be an enormous step toward ensuring equitable access to precious resources. And it is a model for the kind of proactive U.S. policies that will be needed to defuse future conflicts over resource scarcity.

After all, even if Washington doesn’t worry too much about water in the Mekong region, there are several places in the world where scarcity could cause more immediate harm to U.S. interests. One of the clearest examples comes from “land grabs,” in which wealthy multinational conglomerates and governments lease lands in faraway places. According to the International Food Policy Research Institute, from 2006 to 2009, between 15 and 20 million hectares of African land were secured by external agents. In Asia, major leasing agreements have been reached in Cambodia, Indonesia, Pakistan, and the Philippines with governments and companies from South Korea, India, and China. At any time, any of those deals could turn into a point of dispute in an important growth region.

Another example is in India, an emerging economic giant and strong U.S. ally bordering China and Pakistan. Among India’s environmental scarcities, water sits at the top of the list. Due in large part to climate change and to mismanagement of water for agricultural use, India is expected to be water-stressed by 2025 and water-scarce by 2050. If such a calamity were to unfold in India, disease could proliferate and conflict could intensify. In addition, the country might also draw down its current level of engagement in its region, which would have significant repercussions for U.S. foreign policy.

And even in North America, the Rio Grande dividing the United States from Mexico has real foreign policy implications. Although trans-boundary agreements have successfully adjusted to rapid changes in surface water availability, there is no mechanism to manage the unprecedented decrease of groundwater that is rapidly depleting the region’s aquifers. In both countries, agricultural productivity and the supply of water in expanding urban areas are at serious risk.

In other words, the United States can’t afford the reactive approach to resource scarcity. The country -- and all others around the world -- depends on water and other resources for food, ecosystem health, and political security. Earth Overshoot Day provides not only an unsettling annual reminder of the direction in which we’re all heading, but also an opportunity to celebrate the positive steps being taken to reverse the trend. Now, it is in Washington’s best interest to strengthen environmental sustainability as a fundamental tenet of foreign policy. It will give the United States a platform on which to build stronger relationships with other nations, help safeguard the earth’s natural resource base, and support communities around the world who need help securing their basic livelihoods. With the United States taking the lead, we just might make Earth Overshoot Day a thing of the past instead of a barometer of future conflict and disaster.