Two hours from the highway, over a track that in places fades to bare rock, I meet Doña Juanita. A resilient stump of a matriarch four feet tall in straw hat, grey skirt, and worn black loafers, she shares a small compound of wood and adobe huts with her daughter and granddaughter. Their homes on a windy promontory provide a stunning view into shadowed clefts below. We sit in their open-air kitchen, while the two younger women serve tumblers of cloudy agua dulce de maguey. The agave juice ferments into pulque, the home-brewed ur-tequila that relieves and perpetuates the poverty of so many households here. Fresh, it tastes like smoky coconut milk. Bowls of peppery, tomato red broth laced with golden egg yolk strings, and palm-sized tortillas hot from the fire follow. The whole meal, I guessed, grew within thirty metres of this spare home.

For all its beauty, the sierra gives up little to humans without hard effort. Many families keep small herds of thin cattle, whose sharp hooves and voracious appetite for acorns ravage the hillsides. Fields are scratched into slopes as steep as fifty degrees. Burros carry water from a spring at the bottom of the valley up to the family’s compound. Doña Juanita’s grandson once shared the chores with his sister, but like most working-age males in the region he left to find easier, better-paying work in the city. Other young men slip into America. They may be escaping too soon; life and nature here are showing modest improvements. A new solar panel on the roof keeps the canciones coming from a radio, hillsides are being reclaimed by flourishing stands of young pine, and the valley spring has greatly improved. Its flow is clear again, and more reliable.

Martin Granadero, a field manager for one of the ngos the Mexican government hires to care for the reserve, leads me on a ten-minute hike uphill from the restored spring. In the small valley’s upper reaches, hillsides long scored by erosion are now contoured with sinuous terraces, where buffalo grass and pine seedlings take root behind newly planted maguey. “In five years, there won’t be any bare ground here at all,” Granadero says. “In ten years, it will be another world.” Already the stabilized slopes capture far more water for the valley spring, and contaminate streams downhill with far less sediment.

The remote valley’s recovery owes much to the way Mexico has moved past the notion that ecological and social values are necessarily antagonistic to economic ones, and realized instead the urgent need to get the former onto the books of the latter. In 2003, the government recognized that the Sierra Gorda is one of the irreplaceable “water factories” that supply the country’s growing cities and 109 million people. With this in mind, it began distributing $500,000 a year to farmers in upland regions, where rain is captured in streams. Through non-profit groups like Granadero’s employer, Bosque Sustentable, the payments are worth up to $40 a year for every hectare a farmer (or ejido collective) agrees to protect from wandering livestock, fire, and foragers. When the program was renewed earlier this year, its goals expanded to restoring biodiversity. Farmers now must also safeguard their woodlots from poachers.

Such eco-payments are increasingly mainstream outside Canada. Costa Rica and Panama also pay landowners to manage their properties for water production. The European Union, New Zealand, and Australia remunerate farmers for a variety of ecological services, including maintaining biodiversity. The United States’ Conservation Reserve Program spends $1.8 billion a year, giving farmers an average $50 an acre to restore native vegetation along watercourses, among other activities. Helpfully for trading nations, treaties protect such compensation from sanction in what is called a “green box.” Coined by the World Trade Organization, the term has nothing to do with nature, only with permission, as in a traffic light. But the permission is important: because eco-service payments are viewed as legitimate transactions, not baleful subsidies, wto member countries may introduce them without fear of trade retaliation.

Meanwhile, Bosque Sustentable and its parent, Grupo Ecológico, have discovered markets beyond water for the Sierra Gorda’s eco-services. Citing science confirming that young forests capture carbon, Grupo Ecológico has sold carbon offsets to organizations that want to bolster their green bona fides, such as the Triple Bottom Line Investment forum. The money goes directly to the locals who own the forest land. And Grupo has even bigger plans for a “boutique carbon package” with social and environmental elements. Research is under way to quantify precisely how great an improvement in water supply, rare-species habitat, and rural living conditions investors can claim with each unit of the product they buy.

WE ALL LIVE DOWNSTREAM

The exhausted hills of rural Mexico may seem a world apart from rich, prosperous Canada. But look again. Canada’s prime agricultural land would fit into an area not much larger than Montana, a state with less than one-thirtieth of our population. Unwitnessed by urbanites, the soils on which Canada’s harvests rely are being exhausted five to fifteen times faster than they are being replenished. If our industrial parks generally seem cleaner than their Chinese counterparts, it is mainly because we’ve been off-loading our most polluting businesses, even our electronic trash, to Asia. If you include the portion of our ecological footprint we export, the average Canadian uses four to five times our per capita share of the earth’s natural services. Put another way, it would take four or five planets to give every human our lifestyle of flat-screen TVs, big box stores, and drive-thru donut shops — more in places like southern Ontario, Montreal Island, and BC’s Lower Mainland, where we are most densely packed.

Across North America, the housing boom of the new century has exposed the zero-sum nature of our most critical landscapes. For the majority of us, those aren’t the roadless tracts at the top of the Dominion map or the deserts of Nevada. Rather, they’re the green spaces that begin just beyond the last model home. And, as with the Sierra Gorda, most of those green spaces belong to someone and are already fully occupied.

Two provinces, Ontario and British Columbia, have wielded their legal fiats to declare no-go zones for development around their biggest cities. The newest, Ontario’s 7,300-square-kilometre greenbelt, fish-hooks west from the Niagara River around Toronto and back east as far as Cobourg. Inside it, the wheat and corn fields where I biked as a teenager have mostly disappeared beneath spray-on communities branding themselves as tranquil oases insulated from the noisy complexity of urban living. Beyond the greenbelt, real estate companies have already banked much of the unprotected farmland for future leapfrog development.