Extinction, in a biological context, signifies the complete disappearance of a species from Earth, meaning no living individuals remain anywhere in the world. While extinction is a natural process that has occurred throughout Earth’s history, the last 100 years have witnessed a significant acceleration in species loss. This rapid decline is largely attributed to human activities, marking this period as a critical time for global biodiversity. Understanding this recent history provides insight into the profound impact human actions have on the planet’s diverse life forms.
Species Lost in a Century
The last century has seen the irreversible loss of numerous animal species. One prominent example is the Thylacine, also known as the Tasmanian Tiger, a carnivorous marsupial native to mainland Australia and Tasmania. The last known individual died in captivity at the Hobart Zoo in 1936, though the species was officially declared extinct in 1986 following decades of no confirmed sightings in the wild.
Another well-documented loss is the Passenger Pigeon, once incredibly abundant across North America, with flocks numbering in the billions. Intensive hunting led to a catastrophic decline, and the last known Passenger Pigeon, named Martha, died in the Cincinnati Zoo in 1914. The Bali Tiger, a subspecies found only on the Indonesian island of Bali, also vanished, with the last confirmed individual shot in 1937, primarily due to hunting and habitat destruction.
The Golden Toad, a small, brightly colored amphibian endemic to the cloud forests of Costa Rica, was last sighted in 1989 and officially declared extinct in 2004. Its rapid disappearance is strongly linked to climate change and a fungal disease affecting amphibians. Lonesome George, the last known Pinta Island Tortoise, died in 2012, marking the extinction of his subspecies, a direct result of historical exploitation and the introduction of invasive species. The Yangtze River Dolphin, or Baiji, a freshwater dolphin native to China’s Yangtze River, was declared functionally extinct in 2007 after extensive surveys failed to find any individuals, primarily due to habitat degradation and accidental catches.
Primary Drivers of Recent Extinctions
The accelerated rate of extinctions over the past century is largely driven by human activities that alter natural environments. Habitat destruction and fragmentation are leading causes, as expanding agriculture, urbanization, and deforestation convert natural landscapes into human-dominated areas. This process directly eliminates the living spaces and resources essential for countless species, forcing them into smaller, isolated populations that are more vulnerable to other threats.
Climate change also contributes significantly to species loss by altering temperatures and weather patterns, pushing many species beyond their physiological tolerance. Rising global temperatures can lead to habitat shifts that species cannot adapt to quickly enough, disrupting ecosystems and food chains.
Overexploitation, including overhunting, overfishing, and poaching, directly reduces species populations to unsustainable levels. Pollution, from chemicals and waste, contaminates air, water, and soil, poisoning wildlife, disrupting food chains, and causing health issues like reproductive abnormalities.
Invasive species, introduced intentionally or accidentally to new environments, can outcompete native species for resources, prey upon them, or introduce diseases. These non-native species often thrive in new habitats, leading to declines and extinctions of vulnerable native populations. The combined effect of these human-induced pressures creates a complex web of threats that endanger biodiversity on a global scale.
Efforts to Preserve Biodiversity
Recognizing the ongoing crisis, significant efforts are underway globally to prevent further species extinctions and preserve biodiversity. A core strategy involves establishing protected areas, such as national parks and wildlife reserves, which safeguard critical habitats and allow species to thrive free from direct human disturbance. These areas provide refuges for vulnerable populations and help maintain ecological processes.
Captive breeding and reintroduction programs play a crucial role in conserving species on the brink of extinction. Animals bred in controlled environments can be reintroduced into their natural habitats, bolstering wild populations and helping to restore ecological balance. These programs often serve as a last resort for species that cannot survive without direct human intervention.
International agreements and policies, such as the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), work to regulate and monitor the international trade of wild animals and plants. CITES aims to ensure that trade does not threaten species’ survival, controlling the cross-border movement of thousands of species. Public awareness and education campaigns are also important, informing people about biodiversity loss and promoting sustainable practices. These initiatives encourage individual action and generate support for conservation policies, fostering a collective responsibility towards environmental protection.