Many readers will be familiar with the worrisome, white-knuckle wait that comes when you drain your checking account long before payday, the anxiety that builds until the coffers are replenished. That is what all of humanity has signed on for, effective today.

Earth Overshoot Day marks the moment when, according to Global Footprint Network, an independent think tank based in the United States, Switzerland, and Belgium, humanity’s demand for natural resources exceeds the earth’s ability to renew them in a year. As of today, just 34 weeks into 2013, we are officially in ecological overdraft.

Scientists and data-crunchers at Global Footprint Network calculate Earth Overshoot Day by dividing the earth’s current biocapacity (the area of land and water available to produce renewable resources and absorb CO 2 emissions) by the world’s ecological footprint (the area of land and water required to meet humanity’s demand for resources and absorb waste). They then multiply the quotient by 365, the number of days in a calendar year. That number reveals Earth Overshoot Day. This year, that day arrived two days sooner than it did last year. It has come earlier, by about three days each year, since 2001.

Both biocapacity and ecological footprint are measured in global hectares, a common unit that encompasses the average productivity of all the biologically productive land and sea area in the world in a given year. Measurements are drawn from Global Footprint Network’s National Footprint Accounts, datasets for more than 230 countries, territories, and regions that contain more than 6,000 annually gathered data points per country. Although not yet perfect, these accounts provide the most comprehensive available aggregate indicator of human pressure on ecosystems.

Earth Overshoot Day is an approximation, but it is yet one more sign that humanity is consuming the planet’s finite resources at an unsustainable rate. In 2013, humanity requires the equivalent of approximately 1.5 earths to produce the goods and services our lifestyles demand in one year and to absorb the attendant CO 2 emissions and other greenhouse gases. If the United Nations’ moderate projections for growth in population and consumption are correct, we will need two earths before 2050. And that is not even counting on overshooting being aggravated as increased pressure on ecosystems makes less productive land and water available; some ecosystems will collapse even before a particular resource is completely gone.

To be sure, technology has improved biological productivity, but production is still well behind demand. On a global scale, the average person’s ecological footprint has increased since 1961. And available biocapacity per person has nearly halved in the same time. In aggregate, adding up cropland, forest, grazing land, fishing grounds, built-up land, and land available for carbon sequestration -- our accounts are overdrawn. At the same time, energy needs are on the rise, and agriculture production must somehow double by 2050 to keep pace with demand.

It is not shocking that some nations overshoot more than others. The per capita ecological footprint of high-income nations dwarfs that of low- and middle-income countries. The footprint of a typical American is ten times that of a typical resident of an African nation. China’s per capita footprint is smaller than those of countries in Europe and North America but still exceeds the resources that are available per person worldwide. In all, more than 80 percent of the world’s population lives in countries that use more than their own ecosystems can renew. Today’s Japan requires 7.1 Japans to support itself, Italy needs 4 Italys, and Egypt needs about 2.5 Egypts.

Obviously, a challenge of this magnitude requires action from every corner of society -- governments, nongovernmental organizations (NGOs), businesses, and consumers. But where to begin? With the U.S. Congress stalemated, the most traction might come from working with businesses, especially those that are major purchasers of commodities. Simple improvements to efficiency, reductions of waste, and the creation of sustainable supply chains would make a huge difference. At World Wildlife Fund, of which I am the president and CEO, we have signed memoranda of understanding with many of the major companies that are involved in the trade of the commodities that most impact deforestation and marine systems. These agreements involved assessing the risks and opportunities within each company’s supply chains for those commodities that WWF has identified as the most important drivers for environmental conservation. In some cases, companies also promised to reduce carbon emissions. Further, earlier this month, CEOs from 15 companies responsible for producing 70 percent of global farmed salmon announced their commitment to deliver 100 percent Aquaculture Stewardship Council–certified products by the year 2020, in collaboration with the United Nations, the UN Food and Agriculture Organization, WWF, and others.

Businesses are utterly dependent on a reliable supply of natural resources, healthy communities, and the goodwill of a public that increasingly votes for sustainability with its wallet. So, out of pure self-interest, they should care about resource depletion. But that is not the only reason. As counterintuitive as it might seem, this is their moment to shine. Business, arguably more than any other sector, has the influence, money, and agility to begin leading the planet back toward sustainability, and ultimately press governments to enact regulations that matter.

In fact, there are four steps companies should take right now to let go of the myth of infinite resources and help ensure that the earth will still be available to sustain us in a generation or two. First, they should identify resource footprints, set targets for shrinking them, and measure performance against them. Companies manage what they measure. Setting hard targets can catalyze an entire enterprise toward resource efficiency.

Second, they should leverage their influence. A business is only as sustainable as its supply chain, and simply inviting suppliers to follow a company’s lead will not guarantee sustainability. The most effective companies are demanding sustainability as a condition for doing business. Environmental certifications, such as those from the Forest Stewardship Council, the Marine Stewardship Council, Bonsucro, and others, offer ready-made solutions for making supply chains sustainable.

Third, companies should give consumers the sustainability consumers demand. A 2011 study by Cone Communications and Echo showed that 94 percent of consumers want products that are more environmentally responsible. And 93 percent want to know what companies are doing about sustainability. Consumers, especially in emerging markets like China, India, and Brazil, expect companies to take a part in solving environmental issues.

Finally, companies should forge partnerships. No organization can achieve sustainability alone. The area of overlapping interests on a Venn diagram of business, NGOs, and government is surprisingly large. Capitalizing on those interests with long-term, collaborative relationships is crucial to curbing ecological overshooting.

A few companies -- Unilever, Wal-Mart, and Coca-Cola among them -- have begun to demonstrate that it is possible to seek both profitability and sustainability. But capitalism on the whole is mostly concerned with the near term. At this point, though, so should we be when it comes to the earth’s health. Humanity urgently needs markets with the foresight, wisdom, and discipline to help us live within our planet’s means. In the absence of strong regulatory frameworks, companies need to set the pace for this work, and then drive for better government practice over time.

Like a twenty-something living on a credit card until payday, humanity will certainly coast to 2014, when a new “resource year” begins. It is not too late to bring our longer-term resource spending back in line with our finite resources, at least according to current measures. But Earth Overshoot Day is an unsettling reminder that we are closing in on the point of no return. It is time for businesses, and eventually governments, to seize this opportunity for leadership and begin producing more with less. And the rest of us must consume better, wiser, and more conservatively, before we overspend ourselves out of existence.