The world is passing through “Sixth Mass Extinction” or “Anthropocene Extinction”, a biodiversity crisis. The current rate of extinction of species is estimated at 100 to 1,000 times higher than natural background extinction rates. No humans were involved in the earlier five mass extinctions. But the sixth mass extinction is human-made and more immediate than climate destruction.
The Impact Of Humans
Humans have a big impact on Earth and its environment. Humans have the largest geographic range of any mammal, inhabiting all continents, remote oceanic islands, deserts, tundra and rainforest. With 7.8 billion people, humans are among the most common animals on Earth.
Human biomass exceeds that of all wild mammals. Humans are herbivores, piscivores, carnivores, and omnivores. This uninterrupted domination of humans is giving birth to new dangers: pollution, climate change, pandemics and biodiversity loss.
Humans domesticated plants and animals and then cleared forests for agriculture, cities and industries. According to World Bank’s World Development Indicator 2016, since 1990, the world has lost 1.3 million square kilometres of forests, an area larger than South Africa or 1,000 football fields.
According to Earth Day Network, “the situation is dire; forests are being eliminated very rapidly and time is quickly running out”. It is estimated that over 15 billion trees are cut down each year, and the global number of trees has fallen by approximately 46% since the start of human civilisation.
Tropical regions are seeing the fastest loss of forests. Forests are bio-sequesters of carbon dioxide, lungs of mother Earth and homes of biodiversity.
Forests can help us fight pandemics. The world is facing Covid-19, caused by the coronavirus SARSCoV2. The medicinal plants and their bioactive molecules with antiviral properties are a ray of hope to develop drugs against SARS-CoV-2 infection.
Over the years, the human population has drastically increased to 7.7 billion. For centuries, cities were compact with high population densities, and cities grew slowly. This trend has been reversed over the last 30 years.
Today, urban areas around the world are expanding on average twice as fast as their populations. The highest rates of growth in urban areas are forecasted to take place 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 building and will finally result in environmental degradation.
This urbanisation is resulting in loss of habitat, biomass and carbon storage.
Three-quarters of the land-based environment and about 66% of the marine environment have been significantly altered by human actions. In the U.S.A., prairie grasslands are a rich habitat for monarch butterflies. More than 200 million milkweed plants, the caterpillar’s only food source, were destroyed for cropland expansion, which caused monarch’s national decline in the U.S.A.
Groundwater can be an important source in certain types of terrestrial habitats. Loss of groundwater means degradation of such ecosystems. About half the human population relies on groundwater for drinking water and it helps sustain 40% of irrigation systems for crops.
The largest-ever assessment of global groundwater wells by the University of California found that up to one in five were at the risk of running dry. Millions of wells worldwide could run dry with even modest declines in groundwater levels and will have cascading implications for livelihoods and access to reliable and convenient water for individuals and ecosystems.
Approximately 5% of species are at risk of extinction from 2℃ warming. Climate Change associated changes, including flooding, sea-level rise, ocean acidification, ocean warming, droughts and storms, have hugely damaging impacts on biodiversity.
Marine plastic and oil pollution, in particular, has increased tenfold since 1980, affecting 44% of seabirds. This has led to pollution being singled out as the fourth biggest driver of biodiversity loss.
The Impact Of Species Going Extinct
According to the Center for Biological Diversity, when species go extinct, the impact can be dangerous for other species too. For example, when the wolves in Yellowstone Park in California, U.S., were hunted to near extinction by the 1930s, it resulted in multifold population growth of deer and elk; their grazing destroyed habitat for songbirds and caused a decline in the songbird population.
This resulted in an increase in mosquitoes and other insects. Wolves were reintroduced into the park in 1995, after which the wolves balanced the population of elks and deer, 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 main predators of kelp-eating sea urchins. This resulted in a population boom of sea urchins, leading to the extinction of the kelp-eating Steller’s sea cow.
The effects of extinction will worsen in the coming decades. The genetic and cultural variability will change entire ecosystems. When the number of individuals in a population or species drops too low, its contributions to ecosystem functions and services becomes unimportant, its genetic variability and resilience is reduced, and its contribution to human welfare may be lost.
When a species dies out, the Earth’s ability to maintain ecosystem services is eroded to a degree. Species are links in ecosystems through their ecosystem services, and extinction of a species means the other species they interact with may likely face extinction.
Species extinction will affect the human needs of life-supporting stable climate, flows of freshwater, agricultural pest and disease-vector control, pollination for crops, and so on. Let us work for nature, ecosystem restoration and generation restoration for a better future for all.