Human Impact on Ecosystems

Humans (Homo sapiens) are a species that walks upright and has a large, complex brain with a capacity for the use of tools, language, symbolic expression, and culture. Since the evolution of our species, we have been creating environmental changes through subsistence and, within the past 10,000 years, agricultural practices (such as clearing land and selective breeding).

However, most of the significant changes and alterations to ecosystems have occurred within the past century. At present, we continue to change our environment through rapid urbanization, industrialized production, and global trade.

Here we will discuss the impact of human activities on ecosystems: what these activities are, how ecosystems are negatively affected, and what practices are being done to mitigate these negative effects.

Positive and negative human impacts on ecosystems

Human activities have a significant impact on ecosystems, affecting biotic and abiotic factors alike.

By affecting both biotic and abiotic factors, human activities can significantly alter or compromise the function and balance of ecosystems. Let’s discuss a few examples of things that humans do that put tremendous pressure on the environment.

What are the negative impacts humans have on ecosystems?

Human overpopulation

Humans use natural resources –whether for subsistence, trade, or other social, economic, and cultural activities. The exploitation of natural resources can put pressure on the species that depend on these natural resources for their survival.

With the growth of the human population, these impacts are amplified. The widespread loss of species diversity in the past centuries can be attributed to the explosive growth in the human population: from approximately 1 billion in 1850 to over 7.8 billion in 2020. The world's population is projected to grow to 10 billion by 2050.

Additionally, while our technology has advanced such that our food and medicine can increase the lifespan of humans, the challenges caused by human overpopulation increased as well.

Pollution

Many human activities–especially when not properly regulated or managed–create pollution.

Pollutants can be natural or man-made. Natural pollutants include volcanic ash, soot, salt spray, and natural gas. These come from natural activities such as volcanic eruptions, petroleum seeps, and forest fires. Man-made pollutants include garbage, agricultural runoffs, and industrial waste.

Pollution can cause undesirable changes in the air, water, and land alike, which generally harm organisms by altering environmental conditions, to which species respond differently.

Agriculture and fishing

Early agriculture enabled our ancestors to settle in one area and cultivate their own food. This involved clearing tracts of land, domesticating plants and animals, and introducing non-native species to new areas. Clearing land has led to habitat loss, grazing animals has led to the decline in native grasses, and breeding cattle has led to changes in the composition of atmospheric gasses.

On the other hand, the introduction of species where they do not naturally occur (whether deliberately or by accident) can cause competition with the native species. Although the introduction of non-native speciesdoes not necessarily cause harm, it can be a problem if it causes damage to the ecosystem by outcompeting native species for resources necessary for survival, carrying parasites or diseases, or altering abiotic factors such as soil chemistry in the ecosystem.

Fishing is also a vital source of food and livelihood for humans. However, fishing can be unsustainable and can destroy marine ecosystems. Overfishing has depleted fish populations all over the world.

Besides the extraction of fish itself, fishing can also indirectly affect fish and other marine life. Lost or abandoned fishing gear can cause seabirds (Fig. 1) and marine animals to get entangled and deep-sea corals to get damaged. The discharge of ballast water (water contained in the cargo holds and ballast tanks of ships that are used to stabilize ships during a voyage) can also unintentionally introduce invasive species. Additionally, some fishing methods such as bottom trawling and dredging can destroy natural seafloor habitats.

Fig. 1 This albatross chick sits on a small abandoned fishing net. Many sea birds like this albatross chick and other marine life can get entangled in abandoned nets.

The protection of threatened species and habitats is done by preventing or regulating potentially destructive human activities such as hunting, mining, and logging and by promoting sustainable activities such as reforestation, ecotourism, and community-based resource management.

Examples of human impact on ecosystems

We have discussed some human activities that cause a significant impact on ecosystems. This time, let’s discuss how specific ecosystems are affected by different human activities. We will discuss forest, aquatic, and mountain ecosystems as our examples.

Human impact on forest ecosystems

Many forest ecosystems are affected by human settlements and logging.

Tropical forests –which are one of the most diverse habitats on the planet– have long been used by humans for settlement and the extraction of natural resources. In modern times, many tropical forests are subject to land conversion for use as farmland, urban settlements, industrial production, and other human activities.

Land use has caused massive habitat loss and fragmentation (where a large habitat is divided into smaller, isolated habitats). In fact, over half of the tropical forests that existed in the early 1900s have already been destroyed. The destruction of tropical forests generally causes a decline in the abundance and diversity of species that inhabit them.

In addition to tropical forests, temperate broadleaf forests which are found in temperate climates have also been heavily settled on by humans. Almost all of the original deciduous forests in North America have been affected by logging and land clearing for agriculture and urbanization.

Likewise, northern coniferous or boreal forests which are forests that contain cone-bearing evergreens have not been heavily settled by humans but they are affected by logging (Fig. 2), mining, and hydroelectric development projects.

Fig. 2 Habitats like this old-growth forest in Armenia are destroyed by human activities.

Human impact on aquatic (freshwater and marine) ecosystems

Aquatic ecosystems include freshwater habitats like rivers, wetlands, lakes, and swamps as well as marine habitats like oceans, coral reefs, and marine benthic zones.

Lakes have been impacted by agricultural runoff and the dumping of waste.

Coral reefs have been affected by overfishing and the collection of coral skeletons; such activities have caused an alarming decline in coral and reef fish populations. Global warming and pollution which can cause changes in the temperature, salinity and chemical composition of water have also been contributing to the death of many corals. This is because when water temperatures get too high or when there are other changes that put stress on the symbiotic relationship between corals and microscopic algae, the microscopic algae leave the coral tissue and the coral slowly dies.

Human impact on mountain ecosystem

Mountain ecosystems consist of living organisms that can be found on the slopes of mountains. Mountains provide a wide range of habitats that vary with the gradation of mountain slopes: from harsh environmental conditions at higher altitudes to forests, savannas, deserts, or other habitats at lower altitudes.

Human activities that have caused a significant impact on mountain ecosystems include logging, mining, livestock grazing, and energy production. Human activities that use high mountains such as skiing can also cause physical disturbance to the ecosystem.