The negative impacts of humans on the environment

Ever since humans have walked on the Earth, they have changed the environment in one way or another, certainly not to harm or destroy it but rather to be more comfortable. Humans have reshaped the environment through agriculture, travel and urbanization and more recently, the unparalleled introduction of alien materials into the environment. Scientists believe that ‘original nature’ no longer exists. Now as we proceed into the 21^st century, the impacts of humans on the environment are phenomenal.

Basically, human activities that destroy the environment can be broadly categorized into overpopulation and over-consumption, pollution, global warming, agricultural gene modification and deforestation.

1.      Overpopulation and over-consumption

Currently, the worldwide population is estimated to be around 7.7 billion people. By 2100, this number is expected to reach 11.2 billion. Since mortality rates have decreased thanks to better medicine, wider food distribution and better lifestyles, the population has been increasing. Vulnerable nations have the densest populations while richer countries have lower rates of population growth. This makes the situation quite alarming, especially for the environment. More humans mean more resources – food, space, fossil fuels. All that we consume and use come from finite sources. The more we want to have, the greater pressure we put on our environment and more waste is produced. Socio-biologist, Wilson Edward estimates the Earth’s maximum carrying capacity to be around 9-10 billion people ^[1]. Currently, humans are exceeding the Earth’s sustainable productivity by 60%.

2.      Pollution

Pollution is the introduction of foreign material into the environment, which can eventually change it. Sadly, as a result of development and industrialization, humans pollute the environment massively, be it the land, air and water bodies. In China alone, air pollution caused by industrialization has a death toll of 1 million people per year ^[2]. Similarly, marine habitats worldwide are being affected by land-based activities such as the release of sewage and contaminants into oceans, agricultural runoff and dumping of plastic trash. Excessive nutrients into the oceans have created 500 dead zones globally – oxygen deprivation – covering an area of 245,000 km^{2 [3]}.

a)      Acid rain

What’s more, activities like the burning of fossil fuels, manufacturing and the use of heavy vehicle equipment release sulphur dioxide and nitrogen oxides into the atmosphere. These gases mix with condensing clouds and fall to the ground and into water bodies as acid rain. Acid rain can ruin solid materials on land like statues as well as change the soil pH. In many of the developing countries in Asia, where air pollution is quite problematic, a decrease in crop yield and tree growth has been observed as a result of acid rain ^[4]. Nevertheless, the effect of acid rain in water is even worse as it changes the pH of the water which can cause entire marine populations to collapse.

b)      Ocean acidification

Ocean acidification occurs when carbon dioxide mixes with seawater to form a weak carbonic acid. However, this can greatly reduce the pH of seawater leading to deadly effects. In fact, the amount of carbon dioxide in the ocean is now higher than it has been during the past 800,000 years, increasing sea pH by 0.1 unit ^[5]. These changes in pH significantly affect the formation of calcium carbonate which is needed for coral growth and the formation of shells of crustaceans.

3.      Climate change and Global warming

The worst negative impact of humans on the environment is, without a doubt, global warming. Due to an excessive release of greenhouse gases into the atmosphere since the industrial revolution, the planet has been slowly warming up. To add to this, deforestation en mass has also been occurring during the same time period to make way for development, thus leaving the most potent greenhouse gas, carbon dioxide to roam freely in the air instead of being taken up by trees.

As a matter of fact, before pre-industrial times, the level of carbon dioxide was less than 300 PPM; this has now peaked to 440 PPM ^[6]. 97% of climate scientists around the world now agree that changes in the climate are significantly due to human activities. The International Panel on Climate Change states that scientific evidence for warming of the climate is unequivocal. As it is, an increase of 0.9°C in temperature since the late 19^th century is already having severe impacts as in warming oceans, shrinking and melting glaciers, glacial retreat, decreased snow cover, an increase in the frequency of extreme events and sea level rise.

4.      Agriculture and gene modification

As it turns out, agriculture itself has its load of negative environmental impacts like

• point source pollution,
• excessive use of water for irrigation and stream modification,
• use of pesticides and herbicides that leak into water bodies,
• clearance of forests and riparian zones for growing crops,
• grazing by cattle and the
• release of greenhouse gases into the atmosphere by cattle and the use of fossil fuels.

In addition to these, humans have manipulated both plants and animals so as to get better and higher yields and to make them more resistant. Genetically modified organisms are organisms whose genomes have been altered for specific traits that are beneficial to humans. Over the years, there has been a lot of advance in gene modification such that now genes from a different species can be incorporated into an organism in order to get the best results. This has helped greatly in the medicinal and food sector. However, gene manipulation is a very risky process; the outcome may neither be what was intended nor be directly related to the process. What’s more, over the years, even plants and animals have undergone mutation to become more resistant to our products. Superweeds, for instance, are now threatening agriculture by choking crops. 249 species of weeds are now resistant to 22 out of 25 known herbicides.

5.      Deforestation and forest degradation

Sadly, since the 1960s, more than half of the tropical forests have been destroyed. In Europe alone, some 3.7 million hectares of forests have been damaged by cattle, diseases, fire and human activities ^[7]. Every year, 18.7 million acres of forests are lost due to agriculture and illegal logging ^[8]. In point of fact, 17% of the rich Amazonian forest has been cleared during the past 50 years to give way to cattle ranches. Yet, forest clearance and degradation threaten biodiversity directly. Some plant and animal species may go extinct in the wild when their habitats are cleared. Animals, such as elephants, may migrate towards human settlement, cause damage and get killed by frightened and angry villagers.

As it stands, forests are the lungs of the planet. They filter polluted air and release oxygen for life to continue on Earth. With an increase in carbon dioxide level in the atmosphere, there is no argument that forests must expand and be planted. Ironically, houses, hotels, cropland and grazing grounds are now popping up in the places where forests should be.

References:

1. Wolchover, N. (2011). How many people can Earth support? LiveScience. [Online]. Available at https://www.livescience.com/16493-people-planet-earth-support.html [Accessed 23/04/2019]
2. Kao, E. (2018). Air pollution is killing 1 million people and costing Chinese economy 267 yuan a year, research from CUHK shows. South China Morning Post. [Online] Available at https://www.scmp.com/news/china/science/article/2166542/air-pollution-killing-1-million-people-and-costing-chinese [Accessed 23/04/2019]
3. Marine pollution. UNESCO. [Online]. Available at http://www.unesco.org/new/en/natural-sciences/ioc-oceans/focus-areas/rio-20-ocean/blueprint-for-the-future-we-want/marine-pollution/ [Accessed 23/04/2019]
4. Acid rain. Earth Journalism Network. [Online]. Available at https://earthjournalism.net/resources/acid-rain [Accessed 23/04/2019]
5. Fabricius, K.E., De’ath, G., Noonan, S. and Uthicke, S. (2014). Ecological effects of ocean acidification and habitat complexity on reef-associated macroinvertebrate communities. The Royal Society Publishing. [Online]. Available at https://doi.org/10.1098/rspb.2013.2479 [Accessed 23/04/2019]
6. Climate change: how do we know? NASA. [Online]. Available at https://climate.nasa.gov/evidence/ [Accessed 23/04/2019]
7. Deforestation and forest degradation. IUCN. [Online]. Available at https://www.iucn.org/resources/issues-briefs/deforestation-and-forest-degradation [Accessed 23/04/2019]
8. Deforestation and forest degradation. WWF. [Online]. Available at https://www.worldwildlife.org/threats/deforestation-and-forest-degradation [Accessed 23/04/2019]