how a boat is lifted on the答案
剑桥雅思阅读11原文(test1)
READING PASSAGE 1
You should spend about 20 minutes on Questions 1-13, which are bad on Reading Passage 1 below.
Crop-growing skyscrapers
By the year 2050, nearly 80% of the Earth’s population will live in urban centres. Applying the most conrvative estimates to current demographic trends, the human population will increa by about three billion people by then. An estimated 109 hectares of new land (about 20% larger than Brazil) will be needed to grow enough food to feed them, if traditional farming methods continue as they are practid today. At prent, throughout the world, over 80% of the land that is suitable for raising crops is in u. Historically, some 15% of that has been laid waste by poor management practices. What can be done to ensu
re enough food for the world’s population to live on?
The concept of indoor farming is not new, since hothou production of tomatoes and other produce has been in vogue for some time. What is new is the urgent need to scale up this technology to accommodate another three billion people. Many believe an entirely new approach to indoor farming is required, employing cutting-edge technologies. One such proposal is for the ‘Vertical Farm’. The concept is of multi-storey buildings in which food crops are grown in environmentally controlled conditions. Situated in the heart of urban centres, they would drastically reduce the amount of transportation required to bring food to consumers. Vertical farms would need to be efficient, cheap to construct and safe to operate. If successfully implemented, proponents claim, vertical farms offer the promi of urban renewal, sustainable production of a safe and varied food supply (through year-round production of all crops), and the eventual repair of ecosystems that have been sacrificed for horizontal farming.
It took humans 10,000 years to learn how to grow most of the crops we now take for gran
ted. Along the way, we despoiled most of the land we worked, often turning verdant, natural ecozones into mi-arid derts. Within that same time frame, we evolved into an urban species, in which 60% of the human population now lives vertically in cities. This means that, for the majority, we humans have shelter from the elements, yet we subject our food-bearing plants to the rigours of the great outdoors and can do no more than hope for a good weather year. However, more often than not now, due to a rapidly changing climate, that is not what happens. Massive floods, long droughts, hurricanes and vere monsoons take their toll each year, destroying millions of tons of valuable crops.
The supporters of vertical farming claim many potential advantages for the system. For instance, crops would be produced all year round, as they would be kept in artificially controlled, optimum growing conditions. There would be no weather-related crop failures due to droughts, floods or pests. All the food could be grown organically, eliminating the need for herbicides, pesticides and fertilirs. The system would greatly reduce the incidence of many infectious dias that are acquired at the agricultural interface. Altho
ugh the system would consume energy, it would return energy to the grid via methane generation from composting non-edible parts of plants. It would also dramatically reduce fossil fuel u, by cutting out the need for tractors, ploughs and shipping.
A major drawback of vertical farming, however, is that the plants would require artificial light. Without it, tho plants nearest the windows would be expod to more sunlight and grow more quickly, reducing the efficiency of the system. Single-storey greenhous have the benefit of natural overhead light: even so, many still need artificial lighting. A multi-storey facility with no natural overhead light would require far more. Generating enough light could be prohibitively expensive, unless cheap, renewable energy is available, and this appears to be rather a future aspiration than a likelihood for the near future.
One variation on vertical farming that has been developed is to grow plants in stacked trays that move on rails. Moving the trays allows the plants to get enough sunlight. This system is already in operation, and works well within a single-storey greenhou with light reaching it from above: it is not certain, however, that it can be made to work without that overhead natural light.
