(1) Pollution





“The very basis for life on earth is declining at an alarming rate.”

Former UN Secretary, General Kofi Annan

Humans are massively changing the Earth


A 1997 article in the journal, Science, “Human domination of Earth’s ecosystems”, spoke of humanity’s impact on the environment. Up to one half of Earth’s land surface has been transformed by human action.  

The percentage of the concentration of the atmospheric greenhouse gas, carbon dioxide that results from human action.

The percentage of accessible surface fresh water on Earth being put to use by humanity.  The percentage of nitrogen fixation caused by humans is more than all natural terrestrial sources combined.  

The percentage of plant species in Canada that humanity has introduced from elsewhere, i.e., invasive or exotic species.

The percentage of bird species on Earth that became extinct in the past two millennia (largely) from human activity.  

The percentage of major marine fisheries that are fully exploited, overexploited, or depleted.

Ten years after the article, human domination has continued to increase. A 2007 report from the United Nation’s Environmental Program (UNEP) stated: “The human population is living far beyond its means and inflicting damage on the environment that could pass points of no return.” One example: as much as one-third of ocean fisheries are in collapse, two thirds may be so in 2025, and all major ocean fisheries may be gone by 2048. As the “Human Domination” article stated: “The rates, scales, kinds, and combinations of changes occurring now are fundamentally different from those at any other time in history; we are changing Earth more rapidly than we are understanding it. In a very real sense, the world is in our hands and how we handle it will determine its composition and dynamics, and our fate.”

We may ignore pollution if its source is a local factory that provides employment. “That’s the smell of money” we might say. Many of us still fail to recognize our total dependence on our environment or recognize that all human employment depends on nature’s services.

Protecting drinking water

New York City spent hundreds of millions of dollars to buy ~70 000 acres (~28 000 hectares) of land along streams and rivers in the Catskill Mountains to the city’s north – the watershed5 that provides its drinking water.6 It then restricted use of that land, forbidding activities such as the application of pesticides and fertilizers that would pollute watershed streams and rivers.

▪ The city also protected the land from development, leaving trees and grasses in place. Roots of grasses and trees hold the soil in which they grow, preventing it from eroding and running off into streams during rainstorms. Rooted vegetation also slows the rain falling through its foliage down into the soil. Leaf and other vegetation litter on the ground absorb and slow water too. These factors lessen the risk of flooding during heavy rains. And, as water seeps downward to groundwater, the soil traps pollutants contained in the rainwater. Because groundwater is in contact with surface water, keeping groundwater clean helps to provide clean surface water. The rainwater allowed to seep into groundwater replenishes it.

▪ By protecting the Catskills’ from pollution and recognizing the natural water filtration capability of undeveloped land, the City avoided having to build a $6 billion treatment plant to purify its drinking water, plus the $300 million a year it would have cost to run the plant. The City saved billions of dollars by protecting natural services – also called ecosystem services. Other American cities are following New York City’s example, e.g., Austin Texas has purchased 20 000 acres (~8000 hectares) of land around its Edwards Aquifer.

Preventing floods

China is taking similar action to help curb flooding there. Lester Brown described the major 1998 floods along the Yangtze River basin in China, floods continuing for many weeks, and causing many billions of dollars in damage. Afterwards, the Chinese government traced part of the flooding to deforestation along the Yangtze River, so they banned tree cutting in the upper reaches of the basin. They calculated that the value of living trees is three times the value of cut trees.


Global climate change


We will see how important it is to limit atmospheric levels of carbon dioxide (CO2), the major greenhouse gas. Human actions, especially burning fossil fuels, release large amounts of CO2. Regulating the amount of CO2 in the atmosphere requires the protection of trees and other vegetation that take up CO2 from the atmosphere. Tropical forests are especially important. One scientist stated, “We’ll never solve the climate challenge unless we address the loss of tropical forests, [a loss] which puts out as much carbon dioxide as all the planes, trains, and cars worldwide.”

Urban trees

The organization American Forests, using satellite and aerial imagery, showed that tree cover in 20 US cities had declined by 30% over three decades, a disturbing loss of shade, cooling, and aesthetic value. Fewer trees also means more runoff of storm water, which otherwise could seep into groundwater while also removing pollutants. Fewer trees also mean more air pollution because the stomata in tree leaves can help remove air pollutants, and sticky or hairy leaves filter particulates from air.

▪ Using a computer-based geographic information system, American Forests determined how much pollution urban trees remove, and then calculated the economic loss of cutting the trees down. In Washington, DC the cut trees would have removed ~354 000 pounds (over 160 000 kg) a year of major air pollutants including carbon monoxide, sulfur dioxide, and ozone. With fewer trees to trap storm water, storm water runoff increased by 34%. It costs Washington, DC about $226 million per year to trap and treat the additional runoff. Despite tree losses, the average city still has about 30% tree cover, and American Forests believes that this could reasonably increase to at least 40%.

Stabilizing soil depends on more than trees

Grass is also tremendously important for holding soil in place. Indeed, the greatest environmental catastrophe in American history, the “dust bowl”, occurred in the Midwestern states after farmers cleared massive areas of native grasslands. They cleared the grassland to grow ever-increasing amounts of wheat. As long as rainfall was ample, catastrophe was averted, but as the region fell into a prolonged drought in the 1930s, wind whipped up the unprotected soil on 100 million acres (40.5 million hectares) and blew it, sometimes many hundreds of miles away. Untold numbers of farms were destroyed as they were denuded of productive soil. Great numbers of animals, both domestic and wild, died. Humans suffered greatly too, many dying of “dust pneumonia.” Many thousands left the land that could no longer be farmed. US President Franklin D. Roosevelt, in the late 1930s, asked: why did the Great Plains blow away? What made this land die? It was difficult for him to accept that human action was responsible. Beginning in the late 1930s, a major effort began to restore the land, to plant windrows of trees, and to check erosion. However, it took many years for recovery, and some land was never restored. These Midwestern states now largely depend on irrigation to water their crops. The water comes from the Ogallala aquifer, another resource that is being depleted. A fascinating depiction of this tragedy is given by Timothy Egan in his book, The Worst Hard Time.

▪ Undeveloped land provides a multitude of other natural services: home to wildlife, timber for careful lumbering operations, recreation, and aesthetic value. It is also cooler than cleared land.

▪ Undeveloped wetlands, whether located in forests or elsewhere trap eroded soil, preventing its runoff into streams and lakes. Wetland plants and microorganisms purify polluted runoff carried there. Wetlands provide flood protection as noted in the Yangtze example. They also provide habitat to multiple bird and other species.

Other ecosystem services

It is not possible to count the many services that nature provides, notes some major services, and other examples follow.

▪ Nature provides seafood, wild game, forage, timber, biomass fuels, and natural fibers.

▪ Trees and other vegetation take up the greenhouse gas carbon dioxide, while releasing the oxygen necessary to our lives.

▪ The atmosphere’s ozone layer protects us from the sun’s ultraviolet radiation.

▪ Worms and other organisms, and vegetation enhance soil fertility.

▪ Nature provides the insects, birds, and other animals that pollinate many food crops. Birds and some insects eat many agricultural pests.

▪ Many species of fungi and bacteria, insects, and worms degrade organic waste materials, a vital function.

Organic wastes include sewage, dead vegetation, and animal matter, and natural as well as anthropogenic organic pollutants. Some larger creatures eat wastes too - vultures are essential to scavenge dead animals in some places. Waste-degrading creatures could live without humans, but we cannot live without them. Among services that you might not think of, consider glaciers, many of which are now melting as the climate warms. Glaciers provide water to many of the world’s major rivers, which in turn provide drinking water, and water used for agriculture, hydroelectric dams, industry, and, of course, water for the countless other species that live on Earth. Or think about the soil that, in many places around the world is undergoing desertification, conversion into deserts. Desertification lessens the land available for human habitation, for agriculture, or habitat for our fellow species. Moreover, as land undergoes desertification we see increasing numbers of dust storms, often badly impacting people, plants, and animals living hundreds, even thousands of miles from those storms.

Vital species

We do not know which species are absolutely vital to life on Earth, but we know that a great many are needed to maintain the multitudes of ecosystem services.We also know that humanity is destroying and disrupting habitat, and producing pollution. In the process, species are going extinct at a rate perhaps 100 times greater than the natural rate.

▪ Coral is one example of a vital species. Coral reefs play an irreplaceable role in the marine environment.

They provide habitat for marine species that are integral to the ocean’s food chain. They provide a livelihood to a hundred million people in less-developed countries in jobs such as fishing and tourism. Beyond the marine environment, coral reefs protect the coastline from flooding and coastal erosion. But coral reefs are being lost through pollution from eroded soil carried in runoff along with chemical pollutants; global warming is also playing a deadly role.

What are nature’s services?

    Type                                                                              Examples

Provisioning - Food (plants and animals), water, fuel (such as wood and dung).

Regulating - Climate   (including temperature and precipitation), water purification and waste treatment, pollination, preventing soil erosion (as with grasses and trees), storm protection (as with mangroves and coral reefs).

Supporting - Services necessary to produce other ecosystem services including soil formation, nutrient cycling, and production of oxygen (from photosynthesis).

Cultural - Spiritual values, a “sense of place,” recreation and ecotourism.

Nature’s services, also called “ecosystem services”- are the benefits people obtain from the natural world. These services directly affect people and also support services needed to maintain the other services.”


1. In a paragraph, describe how protecting land from development, as New York City did, helps to provide clean water.

2. Coral reefs are a vital living resource that is being destroyed. What is another?

3. What did Harvard biologist, E. O. Wilson mean by saying “We need invertebrates but they don’t need us”?

4. What natural services do the following provide? (a)Grasslands(b)Estuaries(c) Microorganisms.

5. When you think about vital species, what are two species (other than domestic animals)

that come to mind? What services do these species provide?

6. How can pollution result from: Deforestation? (b) Grassland loss? (c) Wetland loss?

7. Technology can mimic some natural services such as purifying water, albeit often at high cost. What technology – one that is already known or one that you can envision – can: (a) Provide clean drinking water at a reasonable cost? (b) Rebuild agricultural soil damaged by erosion? (c) Rebuild soil damaged by salt buildup? (c) Produce adequate food in the absence of fertile soil?

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