Six Ways that Human Activity is Changing the Planet
Wired Science recently outlined six ways in which people are already geoengineering the earth, arguing that the world has moved from the Holocene to Anthropocene era. "From diverting a third of Earth's available fresh water to planting and grazing two-fifths of its land surface, humankind has fiddled with the knobs of the Holocene, that 10,000-year period of climate stability that birthed civilization. The consequences of our interventions into Earth's geophysical processes are yet to be determined, but scientists say they're so fundamental that the Holocene no longer exists. We now live in the Anthropocene, a geological age of mankind's making."
According to Wired Science, there are six forms of human-caused geoengineering already having an impact worldwide:
The human activity most widely viewed as changing the planet is the burning of fossil fuels. In order to produce the energy that drives the world's economy, countries rely on carbon-rich energy sources like coal, oil, and gas. By burning these materials, 40 billion tons of carbon dioxide are added into the atmosphere each year. Right now, atmospheric levels of carbon dioxide are higher than any time in the last 15 million years. Carbon dioxide is a heat-trapping gas, and as a result of these atmospheric changes, average temperatures on the planet are rising and global weather patterns are changing. Some of the carbon dioxide in the atmosphere is absorbed into the oceans, and has altered the acidity of the water. This change has had far reaching affects on oceanic ecosystems and the food chains that support underwater plant and animal life.
Life depends heavily on the supply of fresh water that exists in our rivers, lakes, and aquifers. It's estimated that one fourth of Earth's river basins run dry before ever reaching the ocean as the result of reduced rainfall caused by deforestation and the construction of man-made dams. Less water flowing through river basins has altered local weather patterns.
The Aral Sea, located on the Uzbekistan-Kazakhstan border, was once the fourth largest lake, but has now shrunk by 75 percent. The Aral Sea was once fed by two major rivers which now, due to human activity, run dry before they reach the lake. In the early 1960's, the Soviet Union diverted water from the inflowing rivers to irrigate rice and cotton crops in Central Asia. The reduced water flow caused salt concentrations to increase, making it inhabitable for the fish species that once lived there. The Aral Sea used to absorb heat during the summer and keep the temperature mild during the winters, but now that it is drying up, the local climate is changing. The summers are now longer and hotter and the winters are colder.
For centuries, humans have been engaging in activities that produce black carbon particles that are changing our planet. Black carbon particles are released into the atmosphere in the form of smoke that is produced by cooking with solid fuels, biomass burning, and diesel exhaust. When the black carbon particles reach the atmosphere, they form a heat-absorbing layer that causes temperatures to rise. Raindrops tend to form around black carbon particles in the atmosphere, and when they fall to the ground, they absorb heat on the ground too, thus magnifying the warming effect.
According to Science Daily, Scientists estimate that 25 to 35 percent of black carbon in the global atmosphere was emitted by China and India from the burning of wood and cow dung in household cooking and through the use of coal to heat homes (see an earlier post). Nations that rely heavily on diesel fuel for transportation also contribute large amounts. Wired Science reported that over the last century, Arctic temperatures have risen by an estimated 3.4-degree-Fahrenheit, and scientists estimate that half of this rise can be attributed to black-carbon pollution. It is likely that it has altered weather patterns in a way that's reduced rainfall over South Asia and West Africa. Also, scientists believe that black carbon has played a role in causing Himalayan glaciers to melt, threatening water supplies for hundreds of millions of people.
As the world's population continues to grow exponentially, so to does the amount of farmland needed to provide sufficient food. According to the UN Food and Agriculture Organization (FAO), over 40 percent of Earth's surface is now comprised of agricultural lands, and a large portion of these lands were once covered by forests. Much of Europe, for example, was once covered with dense temperate forests, but over time population growth spurred deforestation to create more farm land was needed.
According to Oxford-based Global Canopy Programme, two billion tons of CO2 enters the atmosphere every year from deforestation. That destruction amounts to 50 million acres destroyed annually, much of which occurring in the Amazon rain forest. Here, the regional cycle of evaporation and condensation has been disrupted, raising the possibility of the remaining forest becoming a savannah. Furthermore, because the rain forest is shrinking, its carbon-dioxide absorbing capacities are being diminished, which in turn means more of the heat-trapping gas is reaching the upper atmosphere, causing global temperatures to rise.
Fertilizers used in farming have also had far-reaching effects. Their use has injected vast amounts of nitrogen and phosphorous into regional ecosystems. Wired Science reports that 120 million tons of nitrogen are removed from the atmosphere each year and 20 million tons of phosphorous is mined from the ground in order to produce fertilizer to be used for farming. These practices add a tremendous amount of nitrogen and phosphorus to the biosphere than would occur naturally. Runoff from farmland often carries large amounts of fertilizer into rivers and streams which eventually drain into the sea. The increase of these elements to ocean ecosystems has been detrimental and is fueling rapidly growing marine dead zones.
Ocean reefs make up the foundation of many marine ecosystems, and their mass extinction is disturbing the flow of nutrients and energy that support animal and plant life in our oceans. As a result of water pollution, ocean acidification, overfishing, and climate change, experts estimate that one-quarter of global reef cover has been lost in the last 50 years and one-third of reef species are endangered. Scientists believe that massive ocean extinction events in the past caused fluctuations in the Earth's carbon cycle that led to changes in climate and weather. The continued destruction of reefs and disruption of ocean food chains jeopardizes the stability of Earth's critical regulatory systems.
Scientists believe that the northwest Mediterranean once supported a vibrant array of plant and animal species. Today, however, the stripped-down ecosystem is dominated by bacteria and jellyfish, which exhibit a reduced capacity to regulate flows of nutrients and energy.
Technological development has led to the invention of new materials, such as plastics, that were previously unknown to the planet. Many of these new materials are made up of chemical compounds that can remain active in the environment for thousands of years and have lasting impacts on the delicate regulatory cycles and ecosystems. Today, the world produces approximately 60 billion tons of plastics each year, and traces of their existence can be found around the globe, even in areas with no human activity. The United Nations estimates that for every square mile of ocean, there are approximately 47,000 pieces of plastic.
At high concentrations, these chemicals can disrupt animal endocrine systems, alter reproduction patterns, and cause cancer. Organic pollutants and plastic-derived endocrine disruptors have been discovered in low concentrations all over the world, even in areas where they've never been used, such as Antarctica and at the bottom of the oceans. While the effects of low doses of there chemicals are less understood, they may act as subtle and widespread stresses that ultimately change the composition of ecosystems.
Image credit: Aral Sea, ABC NewsLink to original post