A global study published in Nature Reviews Biodiversity has revealed a disturbing trend: alien plant species are rapidly overtaking native ecosystems across the tropical world including large parts of India. Driven by climate change and intensified human activity these invasive plants are reshaping biodiversity hotspots threatening both ecological balance and human livelihoods.
The researchers focused on what they call the “Greater Tropics” the tropical and subtropical zones that account for nearly 60% of Earth’s land area and support over a billion people. Alarmingly, these regions now host a rapidly growing number of alien vascular plant species many of which are becoming dominant forces in their new environments.
Since the 1950s, the number of plant species introduced outside their native ranges has grown exponentially, with between 13,900 to 18,500 species now established globally. The study estimates that approximately 9,831 alien plants have already rooted themselves in the Greater Tropics. On many islands including Guam and Tahiti alien flora has now overtaken native species, accounting for as much as 74% of the plant population.
The authors warn that the invasion is being fueled by a dangerous combination of human land use, rising temperatures, and altered rainfall patterns. In India, nearly 66% of natural systems over 750,000 square kilometers have already been impacted by invasive plants, largely due to expanding agriculture, settlement development, and forest fires.
Invasive species like Lantana camara, Prosopis juliflora, and Chromolaena odorata are particularly aggressive across South Asia, replacing native biodiversity and promoting fire-prone conditions. Their expansion is further amplified by global warming, weakening natural resistance in ecosystems and opening doors to even more invaders.
The consequences of this biological reshaping are vast. In the Amazon, invasive grasses such as Brachiaria decumbens have increased fuel loads, exacerbating fires and leading to massive forest dieback. These changes the study notes, risk turning one of the world’s largest carbon sinks into a major carbon emitter.
In India, the semi-arid regions have witnessed how Prosopis juliflora alters food chains. Although its pods serve as emergency fodder for blackbucks during dry spells, these herbivores unknowingly help disperse its seeds, accelerating the alien plant’s spread while reducing native forage.
This self-reinforcing cycle, the authors warn, could accelerate further degradation. “These societal changes form a positive feedback loop between global drivers and the woody transition of savannas, facilitated by alien plants, probably accelerating future plant invasions,” the paper states.
The economic cost of controlling these invasions is staggering. For India alone the estimated budget to manage alien species is US$13.5 billion 36 times its current environment budget.
Scientists are now urging urgent, long-term, and interdisciplinary research across tropical nations to understand the full scope of this biological crisis. They are also calling for large-scale restoration efforts, stronger documentation of invasive species, and greater awareness-building among communities in the Global South.
Without timely action, the ongoing spread of alien species threatens to homogenize some of the planet’s richest and most diverse landscapes, pushing out native life forms and destabilizing ecosystems that humans have long depended upon.