Text B Global Environmental Problems

At the dawn of the third millennium,a powerful and complex web of interactions is contributing to unprecedented global trends in environmental degradation.These forces include rapid globalization and urbanization,pervasive poverty,unsustainable consumption patterns and population growth.Global environmental challenges require concerted responses on the part of the international community.Global climate change,the depletion of the ozone layer,desertification,deforestation,the loss of the planet's biological diversity and the transboundary movements of hazardous wastes and chemicals are all environmental problems that touch every nation and adversely affect the lives and health of their populations.

Moreover,all of these global environmental trends have long-term effects on people and societies and are either difficult or impossible to reverse over the period of one generation.Unless effective global actions are taken early,we will end up plundering our children's heritage and future in an unprecedented way.This text describes five major global environmental problems and points to the potential impact on children and future generations.

Climate Change

It is now widely recognized that global warming over the past 50 years is largely due to human activities that have released green-house gases into the atmosphere.The world's emissions of greenhouse gases,notably carbon dioxide (CO₂ ),continue to increase.The most recent estimates are that atmospheric concentrations of the greenhouse gas carbon dioxide will double or triple pre-industrial levels by the end of this century.As a result,global surface temperature is expected to increase by 1.4 to 5.8 degrees Celsius from 1990 to 2100.

Ozone Layer Depletion

Ozone in the atmosphere's upper layer,the stratosphere,protects humans,animals and plants from the damaging effects of UV-B radiation from the sun.Without it,all life on Earth would cease to exist.However,the use of chlorofluorocarbons (CFCs) and other ozone-depleting substances (ODS) are slowly eating away the stratospheric ozone layer,creating a major potential health hazard.Skin cancer is the most worrisome health impact of ozone depletion.Overexposure to the sun's harmful ultraviolet (UV) light may damage children's skin.

Desertification

Desertification,resulting in part from deforestation,is a significant threat to the arid,semi-arid and dry sub-humid regions of the world—which accounts for 40 percent of the Earth's land surface.More than 250 million people are directly affected by desertification and 1 billion people in more than 100 countries are at risk.These people include many of the world's poorest and most marginalized citizens.In Africa,land degradation is threatening economic and physical survival.

Deforestation

More than 110 million hectares of forest,about 11 million hectares a year,disappeared during the 1990s.Most of this loss was in developing countries.About45 percent of the world's original forests are gone.Major causes of deforestation and forest degradation lie outside the forest sector and include the need to create agricultural land and to harvest fuel wood for food and energy.The removal of trees decreases the ability of the soils to absorb and retain water;it is also intrinsically linked to the loss of biodiversity as original rain forests host numerous species of precious fauna and flora.

Loss of Biodiversity

The variety of life on the Earth,its biological diversity is commonly referred to as biodiversity.It has long been feared that human activity is causing massive extinctions.Despite increased efforts at conservation,it has not been enough and biodiversity losses continue.The costs associated with deteriorating or vanishing ecosystems will be high.However,sustainable development and consumption would help avert ecological problems.

Comprehension Questions:

(1) Which of the following does NOT cause environmental degradation?________

A.Unsustainable consumption patterns.

B.Population growth.

C.Loss of biodiversity.

D.Urbanization.

(2) What kind of greenhouse gas will double or triple pre-industrial levels by the end of this century?___________

A.Carbon dioxide.

B.Sulfur.

C.Chlorofluorocarbons.

D.Methane.

(3) What is the function of ozone layer?_____________

A.Reflect the short wave signals.

B.Conduct electricity.

C.Absorb the UV-B radiation from the sun.

D.Reduce the greenhouse gas emission.

(4) What is the consequence of deforestation?_____________

A.It decreases the ability of the soils to absorb and retain water.

B.It makes the soil more fertile.

C.There are more habitats for animals.

D.It produces more solid wastes.

(5) According to the text,what can prevent the ecological problems?___________

A.No animal killing.

B.Sustainable development and consumption.

C.Conservation of energy and resource.

D.Control the population.