The world is going through a “sixth mass extinction” or “Anthropocene extinction”, a biodiversity crisis. The current rate of species extinction is estimated to be 100 to 1,000 times higher than natural extinction rates. No humans have been involved in the previous five mass extinctions. But the sixth mass extinction is man-made and more immediate than climate destruction.
The impact of humans
Humans have a significant impact on the Earth and its environment. Humans have the largest geographic range of any mammal, inhabiting every continent, remote oceanic islands, deserts, tundra, and rainforest. With 7.8 billion people, humans are among the most widespread animals on Earth.
Human biomass exceeds that of all wild mammals. Humans are herbivores, piscivores, carnivores and omnivores. This uninterrupted domination of man gives rise to new dangers: pollution, climate change, pandemics and loss of biodiversity.
Humans domesticated plants and animals, then cleared the forests for agriculture, cities, and industries. According to the World Bank World Development Index 2016since 1990, the world has lost 1.3 million square kilometers of forest, an area larger than South Africa or 1,000 football pitches.
According to Earth Day Network, “The situation is dire; the forests are disappearing very quickly and time is running out.” It is estimated that more than 15 billion trees are felled every year, and the global number of trees has fallen by around 46% since the beginning of human civilization.
Tropical regions are experiencing the fastest forest loss. Forests are bio-sequesters of carbon dioxide, lungs of Mother Earth and hotbeds of biodiversity.
Forests can help us fight pandemics. The world is facing Covid-19, caused by the coronavirus SARSCoV2. Medicinal plants and their bioactive molecules with antiviral properties are a ray of hope for developing drugs against SARS-CoV-2 infection.
Over the years, the human population has increased dramatically to 7.7 billion. For centuries, cities were compact with high population densities, and cities grew slowly. This trend has been reversed over the past 30 years.
Today, the world’s urban areas are expanding on average twice as fast as their population. The highest growth rates in urban areas are expected to occur in regions that were relatively undisturbed by urban development by 2000. This urban expansion will put pressure on the environment for water, sanitation, energy, transport and construction and will ultimately result in environmental degradation.
This urbanization leads to a loss of habitat, biomass and carbon storage.
Three quarters of the terrestrial environment and about 66% of the marine environment have been significantly modified by human actions. In the United States, grasslands are a rich habitat for monarch butterflies. Over 200 million milkweed plants, the caterpillar’s sole food source, have been destroyed for cropland expansion, causing the monarch to decline nationally in the United States.
Groundwater can be an important source in certain types of terrestrial habitats. The loss of groundwater means the degradation of these ecosystems. About half of the human population depends on groundwater for drinking water and it helps support 40% of crop irrigation systems.
The largest-ever assessment of groundwater wells around the world by the University of California found that up to one in five were at risk of running out. Millions of wells around the world could dry up with even modest drops in groundwater levels and will have cascading implications for livelihoods and access to reliable and convenient water for people and ecosystems.
About 5% of species are threatened with extinction due to 2℃ warming. Changes associated with climate change, including floods, sea level rise, ocean acidification, ocean warming, droughts and storms, have extremely negative effects on biodiversity.
Marine pollution by plastic and hydrocarbons, in particular, has increased tenfold since 1980, affecting 44% of seabirds. This has led to pollution being identified as the fourth driver of biodiversity loss.
The impact of endangered species
According to the Center for Biological Diversity, when species disappear, the impact can also be dangerous for other species. For example, when wolves in Yellowstone Park in California, USA, were hunted to near extinction in the 1930s, it led to multiple population growth of deer and elk; their grazing destroyed songbird habitat and caused a decline in the songbird population.
This has led to an increase in mosquitoes and other insects. Wolves were reintroduced to the park in 1995, after which the wolves balanced the elk and deer population, and finally the plants and songbirds returned to a balanced ecosystem.
Another example of species extinction is the overhunting of sea otters in the Bering Sea. Sea otters are the primary predators of kelp-eating sea urchins. This caused a population boom in sea urchins, leading to the extinction of the kelp-eating Steller’s sea cow.
The effects of extinction will worsen in the decades to come. Genetic and cultural variability will alter entire ecosystems. When the number of individuals in a population or species falls too low, its contributions to ecosystem functions and services become unimportant, its genetic variability and resilience are reduced, and its contribution to human well-being may be lost.
When a species goes extinct, the Earth’s ability to maintain ecosystem services is eroded to some degree. Species are links in ecosystems through their ecosystem services, and the extinction of one species means that the other species it interacts with are likely to become extinct.
Species extinction will affect human needs for stable climate, fresh water flow, control of agricultural pests and disease vectors, pollination for crops, etc. Let us work for nature, the restoration of ecosystems and the restoration of generations for a better future for all.