New Delhi, Dec. 4 -- Invasive species are spreading at an annual rate of 15,000 square kilometres in forest areas and nearly two-thirds of India's natural ecosystems now harbour 11 major invasive species, according to a new study published on Wednesday in the peer-reviewed journal, Nature Sustainability. The species, including Lantana camara, Chromolaena odorata and Prosopis juliflora, are spreading across India at some of the fastest rates recorded globally, said the analysis of a million vegetation records from the National Tiger Conservation Authority's (NTCA) assessments between 2006 and 2022. The study by scientists from the Denmark's Aarhus University, Dehradun-based Wildlife Institute of India (WII) and Bengaluru-based National Centre for Biological Sciences (NCBS) found that every year, a new alien plant invades 6,000 square km of tiger range and 11,700 square km of wild herbivore habitat. It identified 243 subdistricts (tehsils) and 167 protected areas as high-risk zones and added that by 2022, invasive plants have exposed 144 million people, 2.8 million livestock, and 0.2 million square km of smallholder farmland to its devastating impact. Invasive species are plants that take over native species damaged by anthropogenic activities such agriculture land use change and urban expansion, including infrastructure projects and non-anthropogenic events such as fires, floods or droughts. Once established, they suppress growth of native plants and take over the entire ecological space available to them. The study highlighted that climate change and increasing habitat fragmentation was helping spread of the invasive species. In India, the study said the areas of invasive plants such as Chromolaena odorata has also doubled in its range in the Western Ghats and northeast India in less than two decades. In dry regions, Prosopis juliflora, once introduced to prevent desertification, now dominates entire landscapes, outcompeting native shrubs and grasses critical for wildlife and pastoral livelihoods. Many invasive plants believed to have been confined to drier ecosystems are increasingly invading Himalayan areas and wet evergreen forests. Open natural ecosystems like dry grasslands in peninsular India, wet grasslands along Ganga and Brahmaputra, Shola grasslands in Western Ghats, and savannas across India are among the most vulnerable areas, the study said. "At current rates, entire ecosystems could shift from native to invasive dominance within a generation. These plants are moving faster than we can manage or even monitor them," study's lead author Dr Ninad Mungi said. For rural and pastoral communities, invasive plants reduce fodder and fuelwood, lower soil fertility, and even trigger respiratory ailments. For wildlife, dense patches of Lantana and Chromolaena make many forests impenetrable, reduce native food plants, impacting herbivore populations, with cascading effects on predators, disrupting the ecological balance. The authors, including YV Jhala, estimated that India has lost $127.3 billion (Rs.8.3 trillion) to invasive species in the last 60 years and said national policies "recognise" the threat but fail to act in a cohesive manner....