Ocean planet in decline

Vocabulary

waste treatment - удаление отходов, переработка мусора

dilution - растворение вредных выделений в окружающей атмосфере

assimilation – самоочищение воды

non-renewable natural resources – не возобновляемые природные ресурсы

exhaustive – исчерпывающий

nutrient cycling – круговорот питательных веществ

purification plants – очистительные сооружения

soil retention – сохранение земли

circulation patterns – режим циркуляции

capacity of ecosystems – возможность экосистем

maintenance - поддержание

habitable planet – пригодная для жизни планета

buffering – создание защитной зоны

storage capacity – вместимость хранилища

abiotic factors – абиотический фактор

arable land – пахотная земля

abatement of noise – снижение уровня шума

Read the text again and answer the following questions:

1. What does the maintenance of earth’s biosphere depend on?

2. What are the main ecosystem processes on earth can you name?

3. What is the role of ecosystem in the ecological processes on earth?

4. What are ecological processes regulated by?

5. What does a chemical atmosphere on the planet maintained by?

6. How is water regulated on earth?

7. What does life on earth depend on?

8. What are ecosystem processes regulated by?

9. How is climate regulated on earth?

10. What is the role of migration in ecosystem?

Growing human numbers and growing consumption per capita are putting intense pressure on ocean coastal areas, over-consuming ocean resources, and undermining the health of the oceans themselves.

Healthy oceans are essential to a healthy terrestrial environment. The earth's great sea is the heart of the hydrological cycle - nature's solar-driven water pump. About 430,000 cubic kilometres of water evaporate from the oceans every year. Of this amount, around 110,000 cubic kilometres fall as freshwater precipitation over land, replenishing surface and ground waters and eventually completing the cycle by returning to the sea.

The ocean is also the engine that drives the world's climate, storing huge quantities of solar energy in the process. The ocean absorbs and stores carbon dioxide from the atmosphere. Since this invisible gas is one of the main agents of climate change, the ocean is an important sink that helps to modify human impacts on global climate. Ocean currents, the blue planet's super highways, transfer enormous quantities of water and nutrients from one place to another. The Gulf Stream, for instance, pushes more water from the Gulf of Mexico and the Caribbean across the Atlantic into northern Europe, than is carried by all the rivers on earth.

Human populations have a tremendous impact on the quality of coastal and oceanic environments. A full two-thirds of the world's population - 4 billion people - live within 400 kilometres of a seacoast. Just over half the world's population - around 3.2 billion people - occupy a coastal strip 200 kilometres wide (120 miles), representing only 10 per cent of the earth's land surface. With this population distribution, increasing human numbers and mounting development pressures are taking a grim toll on coastal and near-shore resources.

Of Asia's total population of 4 billion, 60 per cent live within 400 km of a coast. Roughly 1.5 billion live within 100 km of the sea. The exceptions are India, Pakistan, and, of course, the land-locked countries of Central Asia. The population of Latin America and the Caribbean is even more clustered on the coasts. The region's coastal states have a total population of around 521 million (in 2006); a full three-quarters of them live within 200 kilometres of a coast.

Among continents, only in Africa do more people live in the interior than along or near ocean coasts. But even in Africa demographic patterns are shifting. Over the past two decades, for example, Africa's coastal cities, as centers of trade and commerce, have been growing in population by 4 per cent or more a year, as they attract people from the countryside.

Over half of the world's coastlines have suffered from severe development pressures, according to a study by the World Resources Institute (WRI) in the mid-1990s. The WRI study used four key indicators to assess risk to coastal areas: cities and population density, major ports, road density, and pipeline density. According to these indicators, the coastlines of most developed countries - particularly Japan, Australia, the United States, Europe and the European part of Russia, were suffering from development pressures and loss of coastal resources. But developing countries fared little better - around virtually all urban areas, coasts were beset by a pattern of pollution and over-development.

Coastal wetlands. The world has lost half its coastal wetlands, including mangrove swamps and salt marshes. Over the past century mangrove forests have been decimated - 25 million hectares are estimated to have been destroyed or grossly degraded. In the Philippines, for instance, the mangrove area has been annihilated by development, dropping by 90 per cent - from one million hectares in 1960 to around 100,000 in 1998.

Mangrove wetlands provide a rich habitat for over 2,000 species of fish, shellfish, invertebrates and plants. Some 80 species of salt-tolerant trees currently occupy about 182,000 square kilometres of intertidal, lagoonal and riverine flatlands throughout the world.

Seagrass beds, the underwater meadows of the ocean, have fared little better. Though no overall quantitative estimates of damage are available, these diverse ecosystems appear in retreat near virtually all inhabited coastal areas.

Coral reefs. Coral reefs, the rainforests of the sea, are also being destroyed in the name of development. Of the world's 600,000 square kilometres of reefs found in tropical and semi-tropical seas, scientists estimate that 70 per cent of them - some 400,000 square kilometres - could be lost within 40 years. Coral reefs are wonders of biological diversity, supporting upwards of one million species and providing humankind with many benefits. They buffer waves and protect shorelines from erosion; they help transfer nutrients from the land to the open ocean; they provide feeding, breeding and nursery areas for many commercially important species of fish and shellfish; and they offer scientists a pharmacopoeia of potential medicines. Yet, they are fast disappearing. In 1997, a global effort to assess the status of coral resources was carried out by Reef Check, organized by Hong Kong University. The study used professional and recreational divers to chart the health of 300 reefs in 30 countries. According to the survey, less than one-third of all reefs had healthy, living coral cover, while two-thirds were seriously degraded. The Caribbean had the lowest rate of living coral, an average of just 22 per cent. Southeast Asia was second, with only 30 per cent of its coral reefs in good to excellent condition; coral reefs in good to excellent condition must have 50 per cent or more of their area in living coral.

Another study by WRI confirmed these findings, observing that the world's most degraded reefs are in Southeast Asia and the Caribbean. In Southeast Asia, for example, one of the epicentres of coral biodiversity, more than 80 per cent of all reefs are at risk. The sea worst hit is the Caribbean. According to a team of British researchers from the University of East Anglia four-fifths of the coral on Caribbean reefs has disappeared in the past 25 years, a phenomenal rate of destruction. Their report, published in Science Magazine in 2003, cites over-fishing, rampant coastal development and pollution as the main reasons for the wholesale annihilation of reef ecosystems.

Coastal erosion. Human activities are eroding close to 70 per cent of the world's beaches at greater than natural rates. Coastlines in developing countries are suffering from serious erosion problems due to unplanned coastal construction, dredging, mining for sand, harvesting of coral reefs for building material and other activities. Erosion is particularly severe along the coasts of Nigeria, Sierra Leone, Liberia, Gambia, Benin and Togo in West Africa. Hundreds of coastal villages have been moved inland as the sea advances. In the Niger River Delta, for instance, erosion claims 400 hectares of land a year and 40 per cent of the inhabited delta could be lost in three decades.

Дата добавления: 2014-11-06