Introducing Invasive Alien Species: Are They a 'Boon' or a 'Bane'?

 

The American Mink is a carnivorous invasive alien species that feeds on rodents, fish, crustaceans, frogs and birds. It is classified as least-concerned in the IUCN Red List. (Image:BBC)

Introduction: Invasive Alien Species (IAS) are plants, animals and other organisms which are not endemic to an environment i.e introduced from outside. They pose a serious threat to endemic flora and fauna. According to the Convention on Biological Diversity (CBD), invasive alien species have contributed to nearly 40% of animal extinctions since the 17th Century.

Characteristics of IAS:

IAS share similar characteristics with the pioneer species i.e the species that first colonise barren habitats, initiating ecological succession. However, several unique characteristics stand out, as given below.

• Rapid Reproduction: IAS show high reproduction rate due to quick disbursal of seeds, spores and asexual reproduction e.g Water Hyacinth doubles in 6-18 days.
• High Adaptability: IAS have high resistance against local pests and pathogens which enables them to thrive in diverse climates e.g Lantana camara grows in every soil.
• Competitive Dominance: IAS easily outcompete native flora and fauna for limited resources such as light, water and nutrients e.g Parthenium releases allelopathic chemicals which can influence the survival and growth of native organisms.
• Altered Ecosystem: IAS have the ability to change the new ecosystem in terms of soil chemistry and water flow which makes it difficult for native organisms to survive e.g Prosopis juliflora, a shrub native to Mexico, South America and the Carribbean, depletes groundwater.
• Lack of Natural Predators: Invasive alien species may not face natural predator competitors in a new ecosystem which facilitates their unchecked growth e.g the African catfish, banned in India, preys on the native fish population.

Examples of IAS:

• Invasive Plants:

1. Kudzu (Pueraria montana): Native to Asia, it is a fast-growing vine that kills native trees and plants.
2. Water Hyacinth (Eichhornia crassipes): An aquatic plant from South America, it blocks sunlight, depeletes oxygen and disrupts the aquatic ecosystem.
3. Japanese Knotweed (Reynoutria japonica): Native to East Asia, it damages public infrastructure like pavements, pillars and walls.
4. Lantana (Lantana camara): A flowering shrub native to tropical America, it forms dense thickets, displacing native plants.

• Invasive Animals:

1. Zebra Mussel (Dreissena polymorpha): Endemic to Eurasia, it clogs water intake pipes and creates water toxicity like botulism that causes muscle paralysis.
2. Brown Tree Snake (Boiga irregularis): Native to Australia, it has led to native bird and lizard populations.
3. European Rabbit (Oryctolagus cuiculus): Originally from the Iberian Peninsula, it causes habitat destruction through over-grazing and burrowing, leading to soil erosion and reduced biodiversity.
4. Burmese Python (Python bivittatus): Native to Southeast Asia, these cause rapid decline in native mammals and birds. 

• Invasive Insects and Microorganisms:

1. Asian Longhorned Beetle (Anoplophora glabripennis): Native to Asia, it primarily targets a wide variety of deciduous trees such as maple, elm and birch, causing significant damage to forests and urban trees in North America and Europe.
2. Asian Tiger Mosquito (Aedes albopictus): Native to tropical and subtropical Southeast Asia, it is known for its ability to transmit diseases such as dengue fever and West Nile virus.
3. Crayfish Plague (Aphanomyces astaci): Native to North America, it is a type of fungus introduced in Europe where it decimated native European crayfish populations.

Pros of IAS:

• Ecological Benefits:

1. Fill the ecological niche of a degraded ecosystem e.g non-native plants provide food to the native animals of an ecosystem where the native ecosystem has already degraded.
2. Provide ecosystem services that can benefit the environment such as filtering water pollutants e.g Zebra mussels can filter large amounts of water.
3. Create micro-climates which may restore the original ecosystem e.g dense thicket of invasive trees provide shade and moisture which may allow native seedlings to grow.

• Socio-Economic Benefits:

1. Create commercial and livelihood opportunities e.g fisheries have been established for Asian carp for human consumption, animal feed and other products.
2. Contain medicinal properties that are used by local communities, supporting health of the local population.
3. Generate recreational opportunities e.g lionfish fishing can be a popular recreational activity.

Cons of IAS:

• Ecological Impacts:

1. Considered to be the second-largest cause of biodiversity loss worldwide, contributing to the decline and extinction of native species.
2. Affect the characteristics of a native ecosystem e.g changing soil chemistry, fire regimes, water availability etc.
3. Create hybrids by intermingling with native species which wipe out the genetic diversity of native ecosystems.

• Economic Impacts:

1. Cause financial losses by destroying agriculture, fisheries and forestry such as damaging crops, killing livestock and reducing timber yield.
2. Damage infrastructure which leads to rising expenses on the repair and maintenance costs e.g Zebra mussel clogs water intake pipes.
3. The cost of managing the IAS is immense requiring significant government funding and labour.
4. Degrade recreational spaces like lakes, parks and rivers, reducing their aesthetic appeal and affecting tourism.

• Social and Human Impacts:

1. Threaten public health as several IAS act as carriers of vector borne diseases like zika and dengue.
2. Affect food security by negatively impacting agriculture and fisheries, especially in developing countries where local livelihoods are tied to these resources.
3. Loss of native species can hurt cultural sentiments of indigenous communities who might have emotional connection with these species.

Initiatives on Tackling IAS:

• Global Initiatives:

1. The Convention on Biological Diversity (CBD) calls on its parties to prevent introduction of alien species which might harm native ecosystems.
2. The International Plant Protection Convention (IPCC) sets international standards to protect plants from pests.
3. The International Maritime Organisation (IMO) regulates shipping to prevent the spread of aquatic invasive species.
4. The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) carries out comprehensive research highlighting the potential role of alien species in biodiversity loss.

• Indian Initiatives:

1. The Biological Diversity Act (2002) empowers the Central Government to regulate the introduction of any exotic species.
2. The National Biodiversity Action Plan (NBAP) includes targets on management strategies for invasive species.
3. Zoological Survey of India (ZSI) and Botanical Survey of India (BSI) monitor invasive species and provide data for policymaking.
4. The Indian Council of Agricultural Research (ICAR) plays an important role in managing agricultural pests and diseases, many of which are invasive.

The Way Forward:

• Strengthen the legal and policy frameworks for comprehensive management of invasive species.
• Harmonize international standards for better monitoring of high-risk pathways like shipping and trade.
• Early detection is necessary which can be enhanced by leveraging new technologies like eDNA, remote sensing and AI.
• Develop comprehensive databases for rapid information exchange and successful management strategies.
• Enhance community action by utilising local knowledge on invasive species. Initiatives like EDDMaps app or iNaturalist can empower people to report alien species.

Conclusion: Invasive alien species not only spoil native ecosystems but also aggravate socio-economic vulnerabilities of people by threatening food security, livelihood opportunities and damaging public infrastructure. The way forward on invasive alien species is to move beyond reactive, piecemeal responses and adopt a proactive, integrated, and collaborative strategy. Doing this will ensure socio-economic justice, while at the same time preserving the biological heritage.