Dear EarthTalk: Do you have current facts and figures about how much rainforest is being destroyed each day around the world, and for what purpose(s)?
—Teri, via e-mail
Pinning down exact numbers is nearly impossible, but most experts agree that we are losing upwards of 80,000 acres of tropical rainforest daily, and significantly degrading another 80,000 acres every day on top of that. Along with this loss and degradation, we are losing some 135 plant, animal and insect species every day—or some 50,000 species a year—as the forests fall.
According to researcher and writer Rhett Butler, who runs the critically acclaimed website, Mongabay.com, tropical rainforests are incredibly rich ecosystems that play a key role in the basic functioning of the planet. They help maintain the climate by regulating atmospheric gases and stabilizing rainfall, and provide many other important ecological functions.
Rainforests are also home to some 50 percent of the world's species, Butler reports, "making them an extensive library of biological and genetic resources." Environmentalists also point out that a quarter of our modern pharmaceuticals are derived from rainforest ingredients, but less than one percent of the trees and plants in the tropics have been tested for curative properties. Sadly, then, we don't really know the true value of what we're losing as we slash, burn, and plant over what was once a treasure trove of biodiversity.
According to the United Nations" Food and Agriculture Organization (FAO), overall tropical deforestation rates this decade are 8.5 percent higher than during the 1990s. While this figure pertains to all forests in the world's tropics, researchers believe the loss of primary tropical rainforest—the wildest and most diverse swaths—has increased by as much as 25 percent since the 1990s.
Despite increased public awareness of the importance of tropical rainforests, deforestation rates are actually on the rise, mostly due to activities such as commercial logging, agriculture, cattle ranching, dam-building and mining, but also due to subsistence agriculture and collection of fuel wood. Indeed, as long as commercial interests are allowed access to these economically depressed areas of the world, and as long as populations of poor rural people continue to expand, tropical rainforests will continue to fall.
Some scientists see light at the end of the tunnel. Joseph Wright of the Panama-based Smithsonian Tropical Research Institute says the tropics now have more protected land than in recent history, and believes that large areas of tropical forest will remain intact through 2030 and beyond: "We believe that the area covered by tropical forest will never fall to the exceedingly low levels that are often predicted and that extinction will threaten a smaller proportion of tropical forest species than previously predicted."
Only time will tell whether Wright's optimistic predictions ring true, or whether a more doomsday scenario will play out. To stay informed and be part of the solution, stay tuned to the websites of Rainforest Action Network, Rainforest Alliance, the Rainforest Site and, of course, Mongabay.com.
Dear EarthTalk: I recently saw a reference to "Enertia houses" that require little in the way of external sources for heating or cooling. Do you have any information on this housing design?
—Alan Marshfield, via e-mail
Enertia is a brand name for homes designed and sold in kits by North Carolina-based Enertia Building Systems (EBS). The idea essentially marries the concepts of geothermal and passive solar heating/cooling into what amounts to a highly energy efficient hybrid system. Architectural inventor Michael Sykes coined the term "Enertia" in the 1980s to describe the innovative homes he was designing that would store solar and geothermal energy and make use of it for most if not all heating and cooling needs.
Under such a system, solid wood walls replace siding, framing, insulation and paneling, while an air flow channel—or "envelope"—runs around the building inside the walls, creating what Sykes terms a miniature biosphere. Inside the envelope, solar heated air circulates, pumping and boosting geothermal energy from beneath the house and storing it within the wood mass of the walls, where it is doled out gradually.
By harnessing the properties of thermal inertia—the ability of materials to store heat and give it off slowly—an "Enertia" house maintains a relatively fixed and comfortable temperature throughout the warmer day (when solar heat is collected and stored) and cooler night (when the wood walls give off heat to keep things toasty as the mercury dips).
The heart of the system is a south-facing sun space within the envelope that is dominated by windows and which therefore soaks up lots of solar energy, filling the house's wood walls with thermal energy that in turn radiates into the primary living space. The entire house functions like an electric heat pump—moving warm and cool air around to accommodate the comfort needs of the occupants. It works even throughout the seasonal changes of the year—with minimal to no fossil fuels consumed or pollution generated.
In one Enertia house in North Carolina, the only power bill the owners typically pay is $35/month for electricity. They also have a back-up in-floor radiant heating system powered by natural gas for long cloudy stretches or unusually cold weather. Gas bills for heat typically total $150 for the year, meaning the owners" total annual outlay for heating, cooling and electricity is less than $600—some $1,000 less than traditional homes in the same zip code are paying, according to data from the U.S. Department of Energy.
EBS markets several different designs for its Enertia houses, but all share the basic premise of primary interior living space heated and cooled by air channeled in from a south-facing "buffer zone" envelope and from below grade. Smaller houses in the line top out at about 2,000 square feet over two floors of living space, while larger ones encompass some 4,000 square feet of living space over three floors. Depending on the model, you could spend anywhere from $66,000 to $292,000 for a complete plan and building materials kit. The rest—including the selection and cost of the land and the labor to build the house—is up to you.
CONTACTS: Enertia Building Systems.
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