Biodiversity loss, a critical environmental issue plaguing ecosystems worldwide, stems from a complex interplay of various factors. At its core, this phenomenon is driven by human activities that exert immense pressure on natural habitats and species. One primary cause is habitat destruction, driven by deforestation, urbanization, and agricultural expansion, which directly diminishes the available living space for countless plant and animal species. Additionally, pollution, including air, water, and soil contamination, poses a significant threat to biodiversity, disrupting ecosystems and endangering species survival. Furthermore, the introduction of invasive species and overexploitation of natural resources exacerbate the problem, pushing vulnerable species closer to extinction. Understanding these multifaceted causes is imperative in devising effective strategies to mitigate biodiversity loss and preserve the rich tapestry of life on Earth.
- The IUCN Red List of 2004 records the extinction of 784 species over the past 500 years.
- Notable recent examples of extinction include all three subspecies of tigers – Bali, Javan, and Caspian.
- Throughout the extensive timeline of over 3 billion years since the origin and diversification of life on Earth, there have been five instances of mass species extinctions.
- The ongoing Sixth Extinction, attributed to anthropogenic activities, is currently underway.
- The present rates of species extinction are estimated to be 100 to 1,000 times faster than in pre-human eras.
- Ecologists caution that if current trends persist, almost half of the Earth’s species could face extinction within the next 100 years.
- The consequences of biodiversity loss in a region are widespread and may include a decrease in plant production, reduced resilience to environmental changes such as drought, and increased variability in ecosystem processes like plant productivity, water utilization, as well as pest and disease cycles.
REASONS FOR BIODIVERSITY LOSS
The loss of biodiversity can be attributed to four primary factors, often referred to as The Evil Quartet: Habitat loss, Overexploitation, Alien species, and Secondary extinction.
HABITAT LOSS
- This stands out as the predominant factor driving animals and plants toward extinction.
- The escalating human population is resulting in the desiccation of wetlands through extensive landfills to meet the growing demand for land.
- Natural forests face clearance for various purposes such as industrialization, agriculture, dam construction, habitation, and recreational sports.
- Notably, tropical rainforests provide stark examples of habitat loss, with their coverage diminishing from over 14% to a mere 6% of the earth’s land surface.
- The Amazon rainforest, often referred to as the ‘lungs of the planet,’ is undergoing rapid destruction, being converted for soybean cultivation or transformed into grasslands for cattle farming.
Man-Animal Conflict
This term pertains to the interaction between wild animals and human populations, leading to adverse effects on people, their resources, wildlife, or their habitats. It arises when the needs of wildlife overlap with those of human populations, resulting in costs for both residents and wild animals.
Causes
- Human population growth and encroachment into forest lands.
- Land use transformation, including industrialization, infrastructure development, and commercial farming.
- Loss, degradation, and fragmentation of species habitats due to the aforementioned reasons.
- Increasing livestock populations and competition with wild herbivores.
- Growing interest in ecotourism and enhanced access to nature reserves.
- Abundant distribution of prey, such as livestock, on the periphery of forest lands.
- Rise in wildlife population due to conservation programs.
- Climatic factors, including habitat destruction induced by climate change.
- Stochastic events like fires and floods.
OVEREXPLOITATION
- Throughout history, humans have relied on nature for sustenance and shelter.
- However, when the legitimate “need” transforms into insatiable “greed,” it triggers the over-exploitation of natural resources.
- Over the past 500 years, the extinction of numerous species, such as Steller’s sea cow and the passenger pigeon, can be attributed to the excessive exploitation by humans.
- In the contemporary context, many marine fish populations worldwide face over-harvesting, posing a threat to the continued existence of several commercially significant species.
- Human activities, driven by the extraction of resources beyond their capacity for replenishment, include the pursuit of whales for oil, fishing for sustenance, logging for wood, and harvesting plants for medicinal purposes.
- Unfortunately, these actions occur at rates surpassing the natural replacement capacity.
- The relentless removal of trees through excessive cutting, overgrazing, the collection of firewood, and the hunting of wild animals for skins (e.g., tigers from the reserve forests of India), as well as ivory, collectively contribute to the gradual loss of species.
- This pattern of exploitation poses a severe risk to biodiversity and ecosystem stability.
INVASION OF ALIEN SPECIES
- The introduction of alien species, whether unintentionally or intentionally, can lead to some of them becoming invasive, resulting in the decline or extinction of native species.
- A notable example is the introduction of the Nile perch into Lake Victoria in East Africa, which ultimately led to the extinction of a unique ecological assembly comprising over 200 species of cichlid fish in the lake.
- Familiar instances of environmental damage caused by invasive weed species include carrot grass (Parthenium), Argemone, Lantana, and water hyacinth (Eicchornia), which pose threats to our native species.
- The recent illicit introduction of the African catfish Clarias gariepinus for aquaculture purposes raises concerns about the potential threat it poses to indigenous catfish species in our rivers.
- The colonization of tropical Pacific Islands by humans is believed to have resulted in the extinction of more than 2,000 species of native birds.
- In India, some invasive fauna includes Eucalyptus in Southern India, goldfish, and the house gecko.
- These species, once introduced, can disrupt local ecosystems and contribute to the displacement or decline of native flora and fauna.
SPECIES EXTINCTION
- Extinction results from diverse processes, categorized into deterministic processes with identifiable causes such as glaciations and human interference like deforestation, and stochastic processes involving chance and random events affecting individual survival and reproduction.
- Unforeseen changes in weather patterns, decreased food supply, diseases, increased competition, predators, or parasites are examples of stochastic processes, acting independently or in conjunction with deterministic effects.
- The impact of these processes relies on the size, genetic diversity, and resilience of populations.
- Traits that elevate a species’ vulnerability to extinction in the context of habitat fragmentation include rarity or low abundance, limited dispersal ability, high trophic status (as higher trophic level animals typically have smaller populations), and low adult survival rates.
- The interplay of these factors underscores the complexity of extinction dynamics.
CO EXTINCTION
- Co-extinctions occur when a specific species faces extinction, putting the plants and animals closely associated with it in an obligatory manner at risk of becoming extinct as well.
- For instance, the extinction of a host fish species can lead to the simultaneous extinction of its distinctive assembly of parasites.
- This interconnected relationship emphasizes the vulnerability of dependent species when their primary host or partner faces extinction.
NATURAL CAUSE
- Natural causes, such as floods, earthquakes, and other disasters, can contribute to the loss of biodiversity.
- These events, often beyond human control, can result in significant disturbances to ecosystems, affecting the survival of various species.
- Floods, for example, may lead to habitat destruction, displacement of species, and alterations in environmental conditions.
- Similarly, earthquakes can cause changes in topography and disrupt ecosystems.
- While these natural causes are part of the Earth’s dynamic processes, it’s essential to recognize the interaction between natural and anthropogenic factors in shaping the current state of biodiversity.
- Human activities, including deforestation, pollution, and climate change, often exacerbate the impact of natural events on biodiversity.
- The complex interplay of natural and human-induced factors underscores the need for comprehensive conservation strategies.
FAQs On Extinction Trends and Causes
Q1: What does the IUCN Red List of 2004 reveal about species extinction?
A: The IUCN Red List of 2004 documents the extinction of 784 species over the past 500 years. Notable recent examples include all three subspecies of tigers – Bali, Javan, and Caspian.
Q2: How fast is the ongoing Sixth Extinction occurring?
A: The ongoing Sixth Extinction, attributed to human activities, is estimated to be 100 to 1,000 times faster than in pre-human eras.
Q3: What are the consequences of biodiversity loss?
A: Biodiversity loss can result in decreased plant production, reduced resilience to environmental changes like drought, and increased variability in ecosystem processes such as plant productivity, water use, and pest cycles.
Q4: What are the primary factors causing biodiversity loss?
A: The primary factors, often referred to as The Evil Quartet, are Habitat loss, Overexploitation, Alien species, and Secondary extinction.
Q5: Why is habitat loss significant for biodiversity decline?
A: Habitat loss, driven by the escalating human population, is the predominant factor leading animals and plants toward extinction.
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