Extreme Weather Events May Be Driving Replacement of Native Species with Exotic Ones

Relevance: GS3, Environment & Ecology, Wildlife & Biodiversity, Climate Change, Impact of climate change on ecosystems, Native Species, Non-native Species, Environmental conservation, Biodiversity conservation

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Why in the news?

• As per recent analysis, extreme weather events, intensified by climate change, are impacting ecosystems by facilitating the replacement of native species with exotic ones.
• Analysis of 443 studies was done covering 1,852 native and 187 non-native species across land, marine, and freshwater habitats.

What are Native Species?

• Native species, also known as indigenous species, are organisms that are naturally found in a particular region or ecosystem without human intervention.
• These species have evolved or naturally migrated to and established themselves in that area over many generations.
• They are part of the natural flora or fauna of a region, meaning they have existed in that region for a significant period, often thousands of years.
• Native species are well-integrated into their local ecosystems. They have established relationships with other native species, including prey, predators, competitors, and symbiotic partners.
• They have evolved characteristics that are well-suited to the local environment, including climate, soil type, water availability, and interaction with other local species.
• Native species play a crucial role in maintaining the ecological balance.
• They contribute to the local biodiversity and help to sustain various ecological processes like pollination, seed dispersal, nutrient cycling, and habitat formation.

What are Non-native or Exotic Species?

• Non-native species, also known as exotic, alien, or introduced species, are organisms that have been brought to an area where they do not naturally occur.
• Unlike native species, non-native species are not originally from the area they currently inhabit. They are introduced by humans, either for agricultural, horticultural, aquaculture purposes, or as accidental introductions through global trade and travel.
• Once introduced, some non-native species are able to adapt to their new environment. Their ability to thrive can vary greatly depending on several factors, including their adaptability, the presence of natural predators, and the characteristics of the new ecosystem.
• Some non-native species become invasive. An invasive species is one that establishes, expands its range, and becomes a pest in the new environment, causing ecological, economic, or human health impacts.
• Non-native species can have significant effects on their new ecosystems.
  • These impacts can be ecological, such as outcompeting native species for resources, altering habitat, or affecting food webs.
  • They can also have economic impacts, such as damaging crops, affecting fisheries, or requiring costly management efforts.
• Examples include plants like kudzu in the United States, animals like the cane toad in Australia, and aquatic organisms like the zebra mussel in the Great Lakes of North America.

Impact of Extreme Weather Events on Different Ecosystems

• Displacement of Native Species by Non-Native Ones: The study, conducted by researchers at the Chinese Academy of Sciences, highlights that extreme weather events are influencing the displacement of native species by non-native ones across land, marine, and freshwater ecosystems.
• Impact on Marine Ecosystems: Marine animals, both native and non-native, generally showed insensitivity to extreme weather events.
  • However, native marine species like molluscs, corals, and anemones were negatively affected by heatwaves.
• Terrestrial and Freshwater Ecosystems: In terrestrial ecosystems, native animals were adversely affected by heatwaves, droughts, and cold spells, showing declines in body conditions, life history traits, abundance, and distribution.
  • Non-native terrestrial animals were mainly affected by heatwaves. In freshwater systems, non-native species were impacted by storms, while native species showed vulnerabilities to most extreme events except cold spells.
• Comparative Resilience: Non-native species exhibited 24.8% positive responses to extreme weather events compared to 12.7% for native species. This suggests that non-native species might be more resilient or adaptable to these changes.
• Reasons for Non-Native Species Resilience: The resilience of non-native species to extreme weather events could be due to their higher growth rates, phenotypic plasticity, competitive abilities, and broader tolerance of disturbances.
• Examples of Impact: The study provides examples like the increased abundance of non-native fish in the Rio Minho estuary, Portugal, following extreme droughts and floods, and the higher flexibility of non-native mesozooplankton species to marine heatwaves compared to native species.
• Plasticity as a Factor: Non-native species often exhibit higher plasticity (the ability to alter behavior, physiology, or morphology in response to environmental changes) than native species, making them less vulnerable to extreme weather events.
• Geographic Bias in Studies: The researchers caution that most studies examined are from North America or Western Europe, suggesting a potential bias in the understanding of these impacts globally.

Native Species vs Non-native Species – A Comparative Analysis

Why Non-native Animals Show Less Sensitivity to Extreme Weather Events Compared to Native Species?

• Higher Tolerance and Adaptability: Non-native or invasive species often have higher growth rates, greater phenotypic plasticity (the ability to change their characteristics in response to environmental changes), stronger competitive abilities, quicker recovery and proliferation, and broader tolerance of disturbances compared to native species.
• Environmental Changes Favoring Non-Natives: Specific environmental changes due to extreme weather events can sometimes create conditions that favor non-native species.
  • For example, severe droughts can increase water salinity, which harms native invertebrates and fishes but benefits salt-tolerant non-native species.
• Greater Flexibility to Environmental Stress: Non-native species may exhibit higher flexibility to environmental stresses like marine heatwaves.
• For example, the invasive South American tomato pinworm, which shows high thermal plasticity (ability to withstand temperature changes) in invaded ranges, and a species of invasive prawn that demonstrated higher plasticity in upper thermal limits compared to native prawns.
• Dominance After Extreme Events: After extreme weather events like droughts and floods, the abundance of native species often declines while that of non-native species increases. This leads to a shift in the ecosystem where non-native species become more dominant.

Conclusion

Non-native species generally show less sensitivity and more positive responses to extreme weather events compared to native species. However, the majority of the studies are from North America and Western Europe, indicating a potential geographical bias in the findings.

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FAQs

MCQs

Q.) Certain species of which one of the following organisms are well known as cultivators of fungi? (UPSC 2022)

(a) Ant

(b) Cockroach

(c) Crab

(d) Spider

Q.) The Himalayan Range is very rich in species diversity. Which one among the following is the most appropriate reason for this phenomenon? (UPSC 2011)

(a) It has a high rainfall that supports luxuriant vegetative growth

(b) It is a confluence of different biogeographical zones

(c) Exotic and invasive species have not been introduced in this region

(d) It has less human interference