As India intensifies efforts to tackle invasive species—from Senna spectabilis in Tamil Nadu’s forests to tilapia and crayfish overrunning freshwater ecosystems—the global scientific community warns that invasions are accelerating worldwide. To understand why managing invasives remains such a complex ecological and economic challenge, TNIE spoke to Julian Blanc, Head, Biodiversity and Land Branch Ecosystems Division of UN Environment Programme (UNEP). In this candid conversation ahead of Seventh Session of the United Nations Environment Assembly, Blanc explains why invasives thrive, how short-term human incentives worsen the crisis, and why he calls biological invasions a “wicked problem” that requires sustained political will and long-term investment.
Here are the excerpts:
The IPBES Invasive Alien Species Assessment report calls invasive species one of the top drivers of biodiversity loss. How do you view these findings in light of global environmental decision-making?
The IPBES assessment reflects exactly what we see on the ground. Invasive species are a classic “wicked problem.” They interact with climate change, land-use pressures, pollution and economic incentives, so you can improve the situation but never fully solve it. And the reality is that none of the major global environmental challenges have the financial resources they require. We’re struggling on the plastic treaty, climate negotiations are falling short, and strong economic interests slow down action. Even when science is clear, as IPBES makes it, converting that clarity into long-term investment and political commitment is the hardest part.
Why is the Indian subcontinent particularly vulnerable to biological invasions?
The Indian region has all the ingredients that make invasions spread faster: densely populated landscapes, heavy pressure on freshwater bodies, rapid land-use change, pollution and multiple competing development priorities. When ecosystems are already stressed, invasives can take hold much more easily. At the same time, many invasive species offer short-term economic value—food, livelihood or market benefits—which creates incentives to keep using them rather than remove them. That combination of ecological pressure and economic pressure is exactly what makes the subcontinent so vulnerable. And once native diversity is lost, the ecosystem functions it supports are lost as well. But honestly, this is not India's problem alone, they are spreading like wildfire across regions in the world.
Many invasive species, including crayfish, are spreading rapidly across wetlands and Ramsar sites. What makes such invasions so difficult to manage?
Invasive species don’t come alone — they arrive alongside multiple pressures already affecting ecosystems. Take invasive crayfish in a Ramsar site: the wetland is already under stress from effluents, intensive floriculture and other human pressures. The crayfish displace native species, yet people harvest and eat them because they have economic value. That creates a paradox: the moment an invasive becomes economically useful, people begin treating it like a resource that must be sustained. This makes eradication much more difficult.
Tilapia is now found in almost every freshwater body in India. How does such a widespread invasion reshape ecosystems?
Tilapia is a good example of an invasive that thrives because of its efficiency. It turns plant matter into animal protein exceptionally fast, making it a cheap protein source. People see clear livelihood and market value in it. But the ecological cost is the loss of native species—fish that once dominated commercial fisheries are now displaced. Each native species provides unique ecological functions, and when that diversity disappears, the ecosystem’s resilience disappears with it. Humanity loses something fundamental, even if the short-term economics look favourable.
Why do governments struggle to act on invasives despite knowing the long-term damage?
Human nature plays a big role. We prefer short-term gains over long-term benefits — we “discount the future.” So people choose $10 today over $15 next year. This behaviour makes it hard to invest in long-term ecological restoration, especially when invasive species appear to offer immediate economic opportunities. And governments face competing priorities: livelihoods, infrastructure, climate adaptation. Invasive species become one more problem in an already crowded agenda.
You have described invasive species management as a “wicked problem.” What does that mean in practice?
Wicked problems have no final solution—you can make things better or worse, but you never “solve” them completely. Invasives spread across political boundaries, ecosystems and sectors, and they interact with climate change, land-use change and socio-economic pressures. What you need is sustained investment, prioritisation and long-term governance. But when these needs compete with other urgent priorities, invasive species often get pushed aside.
The world is struggling to mobilise finance even for climate commitments. How does this affect invasive species action?
That’s exactly why invasives remain underfunded. We are already failing to adequately finance climate action — the plastic treaty negotiations are stuck, COP outcomes fall short, and economic interests like fossil fuels continue to dominate. When climate itself lacks resources, biodiversity and invasive species management get pushed even further down the list. Yet these issues are fundamentally connected. If you don’t manage invasives, you undermine restoration, ecosystem resilience and climate adaptation goals.
Given these challenges, what gives you hope?
Even wicked problems can be made better. We may not eliminate invasives everywhere, but with consistent investment, policy support and prioritisation, we can significantly reduce their impacts and restore ecological function. The question is not whether it’s possible—it’s whether we choose to make it a priority.