Energy efficiency is a term that gets pretty wide use. But what does it mean? Generally speaking, the term indicates getting maximum productivity from a piece of equipment using a minimum of effort or expense. The target goals for achieving efficiency vary according to technology and industry. For lighting, efficiency has meant sources that expend the fewest number of watts over a lifetime while meeting the characteristics of the source (i.e., color temperature and light quality). In this new topical supplement—A|L Energy Efficiency—we take a look at several projects that are using integrative solutions, combining natural and electric lighting to achieve a greater overall luminous efficiency and efficacy.

But lighting is only one part of a much larger discussion about how we use energy. Despite any significant steps we might feel we have taken to reduce our consumption and live in greater harmony with our planet, disasters such as the Deepwater Horizon oil spill in the Gulf of Mexico are a sobering reminder of our complicated relationship with our need for energy.

And yet if you step back and look at our energy needs from a 30,000-foot perch, the issue is not so much about the type of energy but about what we need to produce it. Whether we are talking about using oil, coal, solar, or alternative sources, one constant is water. Without water we cannot produce our energy sources: It is the cooling element needed for steam generation; it is the force that allows hydroelectric turbines to spin; it carries geothermal energy from below the Earth's surface.

The real question is: Do we have enough water to fuel our energy habit? The answer to that is no, the world is running out of water. In the 2008 documentary Blue Gold: World Water Wars, based on the 2002 book Blue Gold: The Fight to Stop the Corporate Theft of the World's Water by Maude Barlow and Tony Clarke, filmmaker Sam Bozzo presents a harsh reality. Water is our lifeline, and the Earth's too; without its sustenance there is no life. It would be easy to blame 20th century industrialization for our dwindling water supply, and that certainly has exacerbated it, but man has a long history of consuming natural resources without replenishing them.

The bottom line is that we are not replenishing our watershed fast enough, given our rate of consumption. Data from 2008 indicates that to meet our water needs, the U.S. pumped 30 billion gallons of water a day out of the watershed. Green regions around the globe are turning into deserts as water is dammed or transported, often at great distances, to drier areas. Agriculture is another huge contributor to the depletion of aquifers, as are deforestation and increased urbanization.

Consider the Aral Sea. Located in Central Asia, it once was one of the four largest inland lakes of the world. In the 1960s, the Soviet Union diverted the rivers that fed it, in order to use the water for irrigation projects. By the early 1990s, the surface area of the Aral Sea had been reduced by half of its original size and had separated into three lakes—the Northern Aral Sea and the eastern and western basins of the once far-larger Southern Aral Sea. By last year, the southeastern lake had disappeared and the southwestern lake was a meager strip of water.

Adding to the complexity of this discussion about water is whether it is viewed as a natural resource or as a commodity. We might think water is a free resource, but it is not. It is owned and managed by private industry. Three companies—Suez Environment, RWE/Thames Water, and Veolia Water—control most of the world's supply through their subsidiary companies, which are contracted by municipalities around the world to oversee the management of their water systems. Water is big business. It's all about the profit and delivery of water, and a whole new geopolitical map is being formed around those who have clean drinking water and those who do not. Water shortages could create global conflict, as has already happened in India, Bolivia, and Africa, and even in the U.S. in places such as Wisconsin, Michigan, and Maine.

Fully 97 percent of the Earth's water is salt water, leaving only 3 percent as freshwater. In addition, a good portion of that freshwater is polluted. The U.S. possesses one of the greatest freshwater sources on the planet—the Great Lakes. These lakes account for 95 percent of our nation's freshwater supply and 20 percent of the planet's. Yet, despite our seemingly abundant access to freshwater, a 2007 United Nations report indicates that by 2025, two-thirds of the world's population will be facing a water shortage. To make water a regularly available commodity going forward, desalination is one possibility. However, only affluent nations realistically will be able to afford the expense of building desalination plants. And while building these plants solves one problem, it creates another; they require a great deal of energy.

Despite our often brutal treatment of the planet and mismanagement of its resources, nature is incredibly resilient and can heal itself if given the chance, with a little help from us. Communities in the American Southwest and West, such as Bolinas, Calif., are adjusting their growth to stay in line with the water table, rather than building indiscriminately.

Architects are also envisioning creative solutions. Martin Felsen and Sarah Dunn, co-founders of Chicago's UrbanLab, have been working on a project they call “Growing Water.” With the city's proximity to Lake Michigan, Felsen and Dunn envision a system of eco-boulevards in which the city can recycle or “grow” its own water.

Energy. It is fair to say it is the debate of our time. It's no longer enough to recycle or be energy vigilant as we track how many watts we use. Going forward we need to be water guardians as well. If we don't know where our freshwater supply comes from and who is controlling that water, then how can we take control of what is at the heart of this debate?: preserving our most precious natural resources so that they remain available and unrestricted for everyone.