- Global extinction takes place when there are no surviving individuals of a species or another taxonomic unit (e.g., subspecies, genus, family, etc., collectively referred to as a taxon).
- The extinction of any species leads to the irreversible depletion of a segment of Earth’s biological diversity.
- Natural occurrences of extinction can stem from unforeseen disasters, persistent environmental challenges, or ecological interactions like competition, disease, or predation.
- Nevertheless, the rates of extinction have surged significantly since humans became the predominant large animal on Earth, becoming the primary driver of global environmental change.
PROCESS OF EXTINCTION
The process of extinction is complex and can be influenced by a combination of deterministic and stochastic factors. Let’s break down the key components involved in the extinction process:
Deterministic Processes:
- Glaciation: Long-term climatic changes, such as glaciation, can have a deterministic impact on species. These changes alter habitats and can lead to the decline or extinction of species unable to adapt to the new conditions.
- Human Interference: Activities like deforestation, pollution, habitat destruction, and overexploitation by humans are deterministic factors contributing to extinction. These actions directly affect the environment and can lead to the loss of suitable habitats or resources for many species.
- Stochastic Processes:
- Weather Patterns: Unpredictable changes in weather patterns, such as extreme events (storms, droughts, floods), can impact the survival and reproduction of species. These events can cause sudden declines in population numbers.
- Food Supply: Fluctuations in food availability, whether due to natural variations or human-induced changes, can affect the survival of species that rely on specific diets.
- Disease: The outbreak of diseases can have a significant stochastic impact on populations.
- This can be especially detrimental if a disease affects a species with a small population size or low genetic diversity.
- Competition: Increased competition for resources, such as food or nesting sites, can be a stochastic factor leading to declines in population size and, ultimately, extinction.
- Predators and Parasites: The introduction of new predators or parasites, whether through natural processes or human activities, can have stochastic effects on populations that are not adapted to these new threats.
Natural Extinction:
- Factors contributing to natural extinction include continent drifting, climate change, tectonic activity, increased volcanic activity, and global glaciations in the late Ordovician period.
- The late Cretaceous extinction is believed to have been caused by an extraterrestrial impact. Vascular plant extinction, compared to animal extinction, has been a more gradual process.
- It is speculated that extinction in this plant group resulted from competitive displacement by more advanced plant forms or gradual climate change rather than sudden catastrophic events.
Artificial Extinction:
- Although species extinction is a natural process that can occur without human intervention, human-induced extinctions now surpass reasonable estimates of natural extinction rates.
- Human activities threaten species with extinction through direct causes such as hunting, collection or capture, and persecution. Indirect causes, including habitat loss, modification, and fragmentation, as well as the introduction of invasive species, further contribute to the artificial extinction of various species.
Vulnerability of Species:
While every species contributes to ecosystem functionality, some are more susceptible to extinction, exerting a greater impact on their ecosystems. The following examples illustrate the vulnerability of certain species:
Large Carnivores and Apex Predators:
- Top predators, also known as apex predators, play a crucial role in ecosystems by regulating trophic levels both directly and indirectly.
- Due to their need for a large territory to secure enough prey, coupled with low abundance and slow reproduction, they are highly vulnerable.
- Fishing pressure, even at a modest level, can lead to substantial declines, with some species experiencing reductions exceeding 90%.
- The critical functions these apex predators perform in disease regulation, ecosystem balance, and biodiversity maintenance highlight the concerns associated with their widespread decline, known as ‘trophic downgrading.’
Specialized Endemic Species:
- Species with a limited geographic range, particularly those specialized in their ecological niche, are highly vulnerable to invasive species and human activities.
- The replacement of these specialized species by non-native, more competitive generalists on a larger scale can lead to the loss of critical ecosystem functions.
Migratory Species:
- Migratory species, such as the Dugong, Loggerhead turtle, Hawksbill turtle, and Mediterranean Monk Seal, rely on suitable habitats in widely separated locations for feeding and resting.
- The loss of any of these habitats poses a significant threat to the survival of these species, emphasizing their vulnerability.
Species with Complicated Life Cycles:
- Certain species, like Tunicates (Ciona intestinalis) and Brown bryozoans (Bugula neritina), have complex life cycles that require specific elements to be present at precise times.
- Disruption of any single element in their life cycle renders them vulnerable, highlighting the delicate balance necessary for their survival.
Consequences of Species Extinction at Local and Regional Scales:
Species extinction at the local or regional level has profound consequences, leading to a decline in both species richness (the number of species) and overall biodiversity. The implications of such extinctions are significant and affect the functioning and stability of ecosystems. Here are key consequences:
- Decreased Species Richness and Biodiversity:
- Local or regional species extinction results in a reduction of the overall number of species and biodiversity in the affected area.
- Impact on Ecosystem Productivity and Stability:
- There is robust evidence indicating that species richness positively influences ecosystem productivity and stability. The extinction of any species can disrupt these vital ecosystem functions.
- Negative Impact on Ecosystems:
- The loss of species, particularly those at higher trophic levels, due to factors like human hunting, habitat loss, or toxic bioaccumulation, can have detrimental effects on the ecosystem.
- Trophic Cascade:
- The extinction of top predators can trigger a trophic cascade, leading to a complete reorganization of the ecosystem and its food web relationships. This can have cascading effects on the abundance and behavior of other species within the ecosystem.
- Challenges in Reintroduction:
- Reintroducing extinct species is not always feasible, as the ecological landscape may have changed, and new species may have taken their place in the food web. This can prevent the successful return of extinct species.
- Alien Species Invasion:
- In some cases, the invasion of alien species may partially compensate for a decline in species diversity. However, the majority of alien invasions tend to involve species at lower trophic levels, which may not fully replace the ecological functions of the extinct species.
Mitigation Strategies for Species Extinction:
- Marine Protected Areas (MPAs):
- Establishment of MPAs, especially Marine Reserves, where all resource extraction is prohibited, to protect depleted, threatened, rare, or endangered marine species and critical habitats.
- Conservation of Critical Habitats:
- Implementation of conservation and ecologically sound management practices for critical habitats, with a particular focus on coastal wetlands, to safeguard essential ecosystems.
- Marine Pollution Prevention:
- Prevention and reduction of marine pollution through integrated coastal and river basin planning, aiming to limit the passage of nutrients and pollutants to the marine environment.
- Sustainable Fisheries and Mariculture:
- Implementation of the FAO Code of Conduct for Responsible Fisheries to ensure sustainable practices in fisheries and mariculture, promoting responsible resource use.
- Prevention of Non-Native Species Invasion:
- Implementation of measures to prevent the invasion of non-native species, which can have detrimental effects on local ecosystems and contribute to species extinction.
- Public Awareness and Education:
- Significant efforts to raise public awareness about the critical need for conservation action. This includes educating people worldwide about the causes and consequences of extinctions and the ongoing loss of biodiversity.
- Adaptive Management of MPAs:
- Implementation of adaptive management strategies for MPAs, allowing for flexibility in conservation measures based on ongoing monitoring and research.
- International Cooperation:
- Collaboration between countries and international organizations to address transboundary conservation issues and ensure the effective protection of shared ecosystems and migratory species.
- Community Involvement:
- Engaging local communities in conservation efforts, recognizing their role in sustainable resource management and fostering a sense of stewardship for the environment.
- Research and Monitoring:
- Continued research and monitoring of species and ecosystems to gather data on population trends, habitat health, and the effectiveness of conservation measures. This information informs adaptive management strategies.
Species Extinction in India:
Flora:
According to the Botanical Survey of India (BSI), 18 plant species have been declared extinct, including four non-flowering and 14 flowering plants.
Notable extinct plant species include:
- Lastreopsis wattii: A fern discovered in Manipur by George Watt in 1882.
- Ophiorrhiza species: Three species from the genus Ophiorrhiza, namely O. brunonis, O. caudate, and O. radican, discovered in peninsular India.
- Corypha taliera Roxb: A palm species discovered by William Roxburgh in Myanmar and the Bengal region.
Fauna:
- Cheetah (Acinonyx jubatus):
- The cheetah, once native to India, is considered extinct in the country.
- Sumatran Rhinoceros (Dicerorhinus sumatrensis):
- The Sumatran rhinoceros is considered extinct in India. The species was historically found in parts of northeastern India.
- Pink-headed Duck (Rhodonessa caryophyllacea):
- Considered extinct since 1950, the pink-headed duck was last recorded in India. The reasons for its extinction include habitat loss and hunting.
- Himalayan Quail (Ophrysia superciliosa):
- Last seen in 1876, the Himalayan quail is considered extinct. Habitat degradation and hunting are believed to be contributing factors to its disappearance.
The extinction of these plant and animal species highlights the ongoing challenges of biodiversity loss in India. Factors such as habitat destruction, climate change, and human activities have played a role in the decline and disappearance of these species. Conservation efforts, habitat restoration, and stricter wildlife protection measures are essential to address and mitigate further losses of biodiversity in the region.
FAQs on Species Extinction:
Q1: What is species extinction?
A1: Species extinction occurs when there are no surviving individuals of a species worldwide, leading to the complete disappearance of that species. It marks the irreversible depletion of a segment of Earth’s biological diversity.
Q2: How does natural extinction differ from accelerated extinction?
A2: While extinction is a natural aspect of the evolutionary process, human intervention has significantly accelerated extinction rates. Natural occurrences can result from unforeseen disasters or ecological interactions, while human-induced impacts, such as hunting and habitat destruction, contribute to the rapid decline of many species.
Q3: What are the consequences of species extinction at local and regional scales?
A3: Local or regional species extinction leads to a reduction in species richness and overall biodiversity. This has profound implications for ecosystem productivity, stability, and the functioning of ecosystems. Negative impacts include trophic cascades, challenges in reintroduction, and the potential invasion of non-native species.
Q4: How does human intervention contribute to species extinction?
A4: Human activities, including relentless hunting, habitat destruction, and over-exploitation of wildlife, significantly contribute to rapid species extinction. These activities push diverse plant and animal species to the brink of extinction, causing an alarming increase in the rate of species disappearance.
Q5: What are deterministic and stochastic processes in the extinction process?
A5: Deterministic processes, such as glaciation and human interference, have identifiable causes and effects on species. Stochastic processes, involving chance and random events, include unpredictable factors like weather patterns, food supply fluctuations, diseases, competition, and predators. Both processes influence the extinction dynamics.
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