Europe, where the so-called population explosion got under way in the 18th century, is once again playing a pioneering role in d

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问题     Europe, where the so-called population explosion got under way in the 18th century, is once again playing a pioneering role in demographic (人口的) development. The continent has the lowest fertility rate and the most elderly population in the world, and this population will soon start to shrink. All this makes it a front runner in a demographic trend that sooner or later will reach most of the world.
    Pioneers have to advance through difficult terrain. Economists are already worrying about the problem of how social security systems will cope when the post-war baby boomers start collecting their pensions in 2015. In hyper-ageing countries like Italy and Germany, where 1 in 7 people will be over 80 in 2050, it is unclear how a shrinking group of young people can generate the wealth needed to support the growing group of elderly citizens. Europe’s competitiveness could fall behind younger and growing populations in other world regions.
    On the face of it, fewer people seem like good news for the environment. The population of Germany, Europe’s most populous country, will shrink by at least 8 million by 2050 and this trend is set to be replicated in many of its neighbours. Remote rural areas, mainly in central and eastern Europe, might become depopulated over time. This should benefit biodiversity as displaced plant and animal species recolonise their old terrain. Given that the world population is still growing by about 200,000 people a day, and the ecological footprint of the human race already lies beyond the limits of sustainability, fewer European mega-consumers will be a blessing for the health of the planet.
    But look a little deeper, and the picture becomes more complicated. Decreasing population does not necessarily promise environmental benefits. The cost per head of population for infrastructure such as sewage systems (污水管道系统) or electricity supply increases when population numbers go down, making clean water and non-polluting energy even more expensive than they are today.
    So can Europe overcome its demographic and ecological challenges at the same time? The solution might be found in a rarely discussed concept: demographic sustainability.
    High population growth, such as that now taking place in many African countries, is not sustainable. But very low fertility rates are unsustainable too. It will be hard for countries with persistently low fertility to remain competitive, creative and wealthy enough to keep ahead of their country’s environmental challenges. What is needed is a middle ground.
    A demographically sustainable Europe needs to have a stable or slowly shrinking population as the existing infrastructure operates most efficiently when the number of inhabitants remains fairly constant. What would it take to achieve this? At present, the average fertility rate in Europe is 1.5 children per woman, and in countries below this line there is an urgent need for family policies to encourage women to have more children. Countries with fertility rates above 1.8, including France, the UK and Sweden, do not need further pro-birth policies as immigrations will fill the demographic gap.
According to the passage, the decrease of population seems to benefit environment in that

选项 A、it reduces the cost of infrastructure
B、it reduces the emission of carbon dioxide
C、it decreases the consumption of natural recourses
D、it provides a good environment for fostering biodiversity

答案D

解析 第三段提到人口数量减少对环境的影响时指出:当曾迁出的动物和植物物种重新占领它们的老地盘时。这可能对生物多样性有利。由此推断出人口数量的;威少为生物多样性提供了有利的自然环境,故答案为[D]。
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