Recent studies reveal rapid invasion of alien plant species in tropical ecosystems. These invasions are reshaping native biodiversity and ecosystem stability. Climate change and human activities accelerate this spread, causing irreversible damage. The Greater Tropics, home to most of Earth’s biodiversity and a billion human livelihoods, face critical threats. Urgent research and restoration efforts are needed to mitigate these impacts.
Extent of Alien Plant Invasion
Alien plants have spread globally, especially since the 1950s. Currently, 4% of all plant species, about 14,000 to 18,500 species, exist beyond their native ranges. The Greater Tropics alone host nearly 10,000 established alien plants. Islands suffer the most; places like Guam and Tahiti have over 60% of their flora as alien species. Other biodiversity hotspots such as Hawaii, Madagascar, and the Caribbean also face dense invasions.
Drivers of Invasion
Human introduction is the primary cause of alien plant spread. Climate change and land use changes further fuel invasions. Moderate climates with high productivity and human disturbance are hotspots. Plants like Lantana camara and Chromolaena odorata thrive in such conditions and have become pan-tropical invaders. In India, agriculture and settlements have altered fire and herbivory patterns, accelerating invasions over 66% of natural areas.
Impact on Ecosystems and Biodiversity
Alien plants replace rich native flora, creating homogeneous ecosystems. This reduces biodiversity and ecosystem resilience. In the Amazon, invasive grasses increase fire intensity, causing forest dieback. Degraded forests lose their ability to act as carbon sinks, contributing to global warming. Woody alien plants also thicken savannas and forests, intensifying fires and further promoting invasions.
Interactions with Native Species
Alien plants disrupt native species through competition and altered food webs. For example, Prosopis juliflora in India reduces native forage but supports blackbuck during dry seasons. These herbivores then help spread the alien plant, creating a feedback loop that harms native vegetation. Such complex interactions worsen native biodiversity loss and ecosystem imbalance.
Future Projections and Challenges
By 2050, alien species are expected to increase by 10-21% in tropical regions of Asia, Africa, and South America. This will expand homogeneous ecosystems and threaten native biodiversity further. Climate change and weakening natural controls will accelerate invasions. Controlling these species requires huge financial resources; India alone needs an estimated US$13.5 billion, 36 times its current environment budget.
Need for Research and Restoration
Scientists urge long-term interdisciplinary research to understand alien plant impacts fully. Strengthening documentation and community awareness, especially in the Global South, is critical. Ecosystem restoration and sustainable land management must be prioritised to protect tropical biodiversity and human livelihoods.
Questions for UPSC:
- Critically analyse the impact of invasive alien species on biodiversity and ecosystem services with suitable examples from tropical regions.
- Explain the role of climate change and human activities in accelerating biological invasions. How can policy frameworks address these challenges effectively?
- What are the socio-economic implications of biodiversity loss in the Greater Tropics? Discuss with reference to livelihoods and ecosystem functions.
- Underline the importance of interdisciplinary research and community participation in managing invasive species. What strategies can enhance restoration of affected ecosystems?
