Poon Watchara-Amphaiwan

Something resembling hope is blooming in Kibera, a densely populated slum in the Kenyan capital of Nairobi. Literally blooming, in the form of homegrown vegetables that can feed impoverished families and their neighbors. The leaves of kale and spinach that our articles editor, Jocelyn C. Zuckerman, sees sprouting in narrow alleyways represent a significant (though largely unreported) global trend: the urbanization of farming. Already, Zuckerman points out in "The Constant Gardeners," "800 million people worldwide currently are engaged in urban agriculture, producing 15 percent to 20 percent of the world's food." The mass migration of populations from the countryside to cities has tipped the planet's demographic balance in favor of urban areas for the first time in our collective history. Drought, water scarcity, and desertification (all of which are intensified by climate change) have accelerated this vast movement. "Less arable land -- and fewer farmers -- means less food," notes Zuckerman. And "hungry people and crowded cities make a combustible mix."

And yet these desperate conditions have produced ingenious solutions -- vegetables grown in recycled grain sacks, for instance, cultivated with recycled domestic waste and sewage water -- offering a lifeline to people on the edge of starvation. That a trend this large and meaningful has received so little attention is astonishing. Yet it is impossible to imagine how the planet can sustainably produce food, 40 years hence, for nine billion people unless urban agriculture, vividly described by Zuckerman, continues to flourish.

The phenomenon of something big and important occurring just out of view takes very different shape in a revelatory account by contributing editor Bruce Stutz, who chronicles the life of one of the sea's most astonishing creatures: the Atlantic sturgeon. This "massive armored" fish -- which can grow to eight feet, weigh 600 pounds, and live past 60 years of age -- has navigated the earth's rivers and seas for approximately 85 million years. Yet in little more than 100 years it was hunted almost to extinction by fishermen in pursuit of its increasingly valuable roe (processed into caviar). "Some have compared the carnage," writes Stutz, "to the massacre of the buffalo." Within the next 20 years, certain populations of this animal could vanish. But will they? The prospects for their survival depend on understanding where they reside, their patterns of migration, and how these behaviors vary among geographically distinct populations -- and on acting accordingly through regulatory oversight. In an age of mass extinctions, how could we risk losing an animal of such magnificence, even if we don't yet know every last detail of its predicament?

In both the human and the animal realms, in other words, our leading experts are working to decipher the still infinite mysteries of our planet. That the survival of so many depends on new knowledge and innovations -- on land and at sea, among Africa's hungry millions and the sea's diminished bounty -- tells us something about the unprecedented urgency of their endeavors.