Types of Harmful Human-Environment Impacts: Part 2

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During the past two hundred years, we humans have brought about four major kinds of harmful impact on our natural environment:

  • Habitat loss and fragmentation;
  • Pollution, including greenhouse gas emissions;
  • Biotic changes;
  • Exploitation and extinction of wild living resources.

Although we have made these kinds of impacts since we began as a species, they have not been a problem until we multiplied our population, increased our appetites, and expanded our technological capabilities (I=PAT). Let’s discuss each of these types before beginning the more rewarding, but also more challenging task of resolving these problems, and moving into closer harmony with our natural world.

Habitat loss and fragmentation

Much of all human activity involves habitat loss and fragmentation: resource extraction (mining, oil and gas, logging, and fishing), agriculture, cities and towns, transportation, communication, and energy networks, and dams and reservoirs. In all these activities, humans substantially modify the natural environment to achieve their purposes.

According to an article in Science Magazine , “Human alteration of Earth is substantial and growing. Between one-third and one-half of the land surface has been transformed by human action [and] more than half of all accessible surface fresh water is put to use by humanity. … By these and other standards, it is clear that we live on a human-dominated planet.”

Although some habitat loss and fragmentation is necessary for human survival, we are only now coming to realize fully the disastrous consequences of some of our past practices. For example, “clear cutting” or cutting down all the trees in a forest being harvested may be very efficient for a logging company, but catastrophic for the environment (for example, loss of biodiversity, extinction of species, less sequestering of carbon emissions, and a greater chance of both fire and flood).

Just such a scenario was reported last March on western Vancouver Island concerning a patch of old-growth forest that was clear cut. After a fire swept through the exposed clear cut area last summer, subsequent rains leached through the ground, “leaving an ecological wasteland.” It is noteworthy that the “old-growth standing timber next to the clear cut survived the fire.”

Pollution, including greenhouse gas emissions

The other side of the human resource extraction/production/distribution/consumption equation is disposal and/or pollution. Whereas disposal is relatively safe, pollution involves the act of contaminating or otherwise harming the environment. It is neither an absolute nor a static concept; it is a human construct that changes over time and circumstance. Consider the air we expel. Is it pollution? No, but what about other emissions that were thought to be safe, but are now harmful? In some cases, like DDT, either current knowledge or measurement was insufficient to evaluate these emissions adequately, while in other cases, such as human sewage, there was not enough critical mass to render them harmful.

Where do greenhouse gas (GHG) emissions fit into this discussion? According to the World Meteorological Organization , “the burning of coal, oil, and natural gas, as well as deforestation and various agricultural and industrial practices, are altering the composition of the atmosphere and contributing to climate change. These human activities have led to increased atmospheric concentrations of a number of greenhouse gases, including carbon dioxide, methane, nitrous oxide, chlorofluorocarbons, and ozone in the lower part of the atmosphere,” which have generally produced an overall warming effect.

How is climate change attributed to human activity? Figure 5.1 reveals an analysis of air trapped in core ice samples between the years 800 and 2000. The results clearly show a rapid build-up of carbon dioxide in the atmosphere that coincides exactly with the onset of the industrial revolution in Europe during the late 18th century.

The full implications of climate change for human existence on the planet remain to be seen, but like the Titanic about to hit the iceberg, some of its effects are now irreversible.

In Canada, the largest single source of greenhouse gas emissions is the Alberta oil sands project. According to a report by the Canadian Association of Petroleum Producers, “The oil sands industry currently accounts for approximately 0.1 per cent of global emissions which is 5 per cent of Canada’s total GHG emissions. Increasing production will see emissions from the oil sands grow to 8 per cent of Canada’s total emissions by 2015.”

Over the course of the 20th century and particularly in recent decades, governments, industry, and grassroots organizations have come to the horrible realization that what we first thought were safe disposal practices were later identified as being extremely harmful – both to ourselves and the environment. One thing though is certain: Increasing rates of extraction, production, distribution, and consumption necessarily cause greater rates of disposal and pollution. How we deal with this problem is key to our survival.

In my next post: Biotic changes and Exploitation and extinction of wild living resources.


Alan Hedley is a retired University of Victoria Sociology Professor. He’s currently searching for ways to contribute to a more equitable and sustainable human existence on planet Earth – and blogging about his journey.

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