According to the World Wildlife Fund, people are currently using resources 25 percent faster than they can be replaced. If we continue down this course, we will need a second planet by the year 2050. Sustainable communities attempt to change that course by drastically altering how citizens interact with the environment. Alternatively known as green communities or ecovillages (生态村), sustainable communities vary in their approaches to sustainable living, or a way of life that meets the population’s basic needs in ways that can be continued indefinitely for future generations. Some communities focus solely on enriching the environment, while others also aim to improve social and economic conditions as well. Sustainable communities generally strive to minimize waste, reduce consumption and preserve open space. Ideally, they don’t use resources faster than they can be replenished, and they don’t produce waste faster than it can be assimilated back into the environment. Granted, some communities are more radical than others--living entirely off the grid and eschewing the use of government:--printed money--but the basic principles are similar. Designing the neighborhood to encourage walking or bicycling is one way sustainable communities put these first two principles into practice. Less driving means less gas and emissions. Many ecovillages also incorporate work space into homes or encourage telecommuting. They also might zone part of the development for commercial use, essentially making the community a serf-contained environment where residents don’t even have to leave for shopping or entertainment. This design sometimes is called a live- work-play lifestyle. Using green building techniques is another staple of sustainable communities. Here are a few examples: ・ Architects design buildings to take advantage of the sun’s lighting and heating capabilities. ・ They install energy-efficient appliances. ・ They try to use local sources of materials as much as possible to cut back on the environmental costs of transport. ・ They build with durable, non-toxic materials that have either been recycled or sustainably harvested. You might see straw bale (草捆) houses, which essentially use bales of straw as the structural building blocks; cob houses, which are a mix of straw, clay and sand or earthbag homes, which are exactly what they sound like, homes made out of bags of dirt. Along with green building techniques, sustainable communities rely on green gardening methods. They landscape with native, drought-tolerant plants and raise them organically to reduce water and keep pesticides and herbicides out of the environment. Many communities also set aside a significant portion of their land as open space. Serenbe, for example, reserves 80 percent of its 900 acres for green space, that is, 720 acres of rolling hills, woods and streams free of development, quite a contrast to the concrete-laden urban sprawl of Atlanta just 32 miles away. Another way sustainable communities reduce their ecological footprint is by capturing and recycling their wastes, often creating their own contained natural cycles. Instead of treating normally perceived waste products such as rainwater and sewage as pollution to be gotten rid of, residents mm them into resources. Sewage, for example, is turned into compost that fertilizes plants and increases soil productivity, while captured rainwater is cleansed through innovative filtering systems and reused for watering plants. More than 400 ecovillages exist in the world, according to the Global Ecovillage Network database. The following examples outline life in just two of these communities. Dancing Rabbit Ecovillage, Missouri. Dancing Rabbit Ecovillage is a developing 280-acre community in northeastern Missouri with far-reaching goals. It aims to be an entirely self-reliant town that practices "radical environmental sustainability’, according to the community’s website. The town’s founders hope to attract between 500 and 1 000 residents to create a diverse community more capable of providing for all of its own needs. Dancing Rabbit even has its own local currency to encourage local trading and sourcing of jobs. The ecovillage has established a set of six guidelines that may seem extreme to the lazy environ- mentalists among us, but should set the town well on its way towards achieving sustainability. 1. No vehicles are to be used or stored in the village. 2. Fossil fuels for cars, refrigeration, heating and cooling homes, as well heating domestic water aren’t allowed. 3. All gardening must be organic. 4. All power must come from renewable resources. 5. No lumber from outside the local area is allowed unless it is recycled or salvaged. 6. Organic waste and recyclable materials are to be reincorporated into usable products through composting methods. Long term, Dancing Rabbit citizens are trying to achieve negative population growth. If they want the current 50 or so residents to become 500 or I 000, they may want to rethink that last guideline. Los Angeles Ecovillage, California. You might think sustainable communities have to be set in the country, but that’s not true. Located just three miles west of downtown Los Angeles, the Los Angeles Ecovillage (LAEV) is a community of 500 residents seeking to have minimal impact on the environment while also providing a fulfilling way of life. The urban location near public transit, schools, churches, commercial services and industry helps residents drive less, while the dozens of gardens and fruit trees provide a local source of food. LAEV takes a whole-systems approach to sustainability, meaning that residents strive to balance’ the social, economic and environmental needs of the community. Here, clean water and air rank up there with close-knit relationships, ethnic diversity and affordable housing. Citizens have saved 20 tons of brick from the landfill to use in construction projects, composted over 100 cubic yards of yard waste and held countless weekly potluck dinners to establish and strengthen relationships. Who knew that sustainability could be possible even in one of the largest, most polluted cities in the United States Residents of the two sustainable communities we just discussed deliberately placed sustainability at the top of their agenda. But communities spring up for lots of reasons not related to the environment, and sometimes the Earth benefits. Before "green" was the new buzzword and sustainability was cool, Old Order Amish communities were quietly co-existing with the planet since the early 18th century. While members of this religious group didn’t consciously develop their way of life to help the environment, their simple farm-based living doesn’t hurt it. The Amish use horses to power their farm equipment and to get around. Their homes have no electricity; instead, they use lanterns (灯笼) for light. In stark contrast to the rampant consumerism visible in many countries, the Amish do not own things they don’t need. They wear simple clothes, and their houses are sparsely furnished. Amish communities didn’t have to "return to the earth" to achieve their brand of sustainability. They were there all along. Cohousing developments offer another example of a living arrangement that unwittingly(未觉察地) practices sustainability. These developments typically are designed to encourage and strengthen social relationships, rather than to tread lightly on the environment, but, as it turns out, the two often go hand in hand. Although residents in a cohousing development enjoy the privacy of their own homes, they share a common building and other resources. Sharing major appliances like washing machines, power tools and heavy exercise equipment forces you to interact with your neighbors while reducing resource use. In addition, it allows individual houses to be smaller, which, along with the clustered arrangement of homes, preserves land. People who own cars (some people share cars) park them on the sides of the neighborhood to create a pedestrian friendly environment safe for children. Several times a week, residents may also eat a shared meal in the common building to strengthen ties. Cooking for many on one stove is much more energy efficient than cooking for 20 on separate stoves.What will happen in the middle of the 21st century, if we consume resources much faster than their replacement A．We can have another planet called the Earth.B．We will use up resources on Earth.C．We will work out replaceable resources.D．We will migrate to another planet to live.