“Look closely at nature. Every species is a masterpiece, exquisitely adapted to the particular environment in which it has survived. Who are we to destroy or even diminish biodiversity?” The quote by EO Wilson, a pioneer biologist, emphasizes the intrinsic value of every species and its role in maintaining biodiversity and ecosystem balance. All species, including humans, are integral to the web of life, each contributing to ecosystem resilience. As humans, we hold immense power over nature, yet this power comes with the responsibility to protect biodiversity rather than diminish it.
Our actions, such as habitat destruction and the spread of invasive species, disrupt ecosystems and threaten our own survival, highlighting the ethical imperative to preserve the intricate interdependence of life.
Invasive alien species (IAS) are non-native organisms introduced to new habitats through human activities, intentionally or accidentally, that disrupt ecosystems and threaten biodiversity. Without natural predators, IAS often proliferate rapidly, outcompeting native species and driving them to extinction. Their spread causes irreversible biodiversity loss, alters ecosystem services and incurs colossal economic and social costs. Globalization, trade, travel and climate change have further accelerated IAS spread, making them one of the top five drivers of biodiversity loss, contributing to native species extinction, noted by IPBES, 2019. Globally, around 37,000 IAS are established.
Pyšek et al (2020) reported that around 14,000 species with established alien populations represent four percent of global flora, while 175 terrestrial gastropods as IAS across 56 countries, 745 of 15,000 freshwater fish species, and 971 out of 2000 bird species have become established IAS across various regions.
Growing global perils
IAS are major drivers of biodiversity loss and native species extinction, often referred to as ‘biological pollution’ or ‘green cancer’ (Olson, 2006), while also posing risks to human health, food security and livelihoods. For example, the brown tree snake (Boiga irregularis) led to the extinction of 10 bird species on Guam after its introduction in the 1940s. The IAS Asian tiger mosquito (Aedes albopictus) spreads diseases—Dengue, Chickungunya, and West Nile virus, affecting millions globally. Water hyacinth (Eichhornia crassipes), native to South America, introduced for ornamental purposes across the world, invades water bodies, irrigation channels and rice paddies, causing ecological and economic calamity. IAS disrupt critical ecosystem services such as pollination, water purification and soil fertility, essential for natural cycles. Their spread, accelerated by global trade and travel, worsens these risks, undermining public health and economic resilience.
Economic toll associated with IAS is staggering. A study by Diagne et al (2021) in Nature estimated biological invasions have caused a minimum global economic cost of $1.288trn between 1970 and 2017. According to the IUCN, IAS cost €12.5bn annually and Australia AUS$13.6bn each year. Invasive insects alone account for $70bn in global annual losses. IAS damages agriculture, reduces fishery yields, and disrupts urban areas, leading to financial losses and increased management costs. Prominent IAS in the US, including the spotted lanternfly, red fire ant, feral swine, Emerald ash borer,
Asian carp and Burmese python, purple loosestrife, Japanese honeysuckle, barberry, English Ivy and Kudzu have altered ecosystems and incurred billions of dollars in control efforts and lost productivity. IAS like zebra mussels, native to the Caspian Sea, damage aquatic ecosystems, while the Spanish slugs devastate crops in Europe with massive economic damage.
Furthermore, IAS threaten food security and livelihoods, hindering progress toward the UN's SDG 15 aiming to protect life on land and below water. The IUCN Red List of Threatened Species (2022) reports that one in ten species on the list are threatened by IAS, emphasizing the urgent need for coordinated global efforts to mitigate their spread protecting ecosystem resilience.
The context of Nepal
IAS pose escalating threats to Nepal’s ecology, economy, sustainable development and health, reflecting global concerns. IAS in Nepal have a long history, with Chomolaena odorata (Siam weed) first reported in 1825. Known locally as ‘Banmara’, these species disrupt ecosystems, outcompete native species, and threaten agricultural productivity. An estimated 219 alien flowering plant species in Nepal’s forests, with 30 flora species are common IAS (Yadav et al, 2024). Budha 2014 reported 69 fauna species; insects (21), fish (16), birds (three), wild mammals (two), freshwater prawn (one), platyhelminthes (one) and livestock breeds (25 improved breeds), identified as common IAS. These species are primarily from the Americas (74 percent), Europe (one percent) and Africa (eight percent) and cause irreparable harm to ecology.
The introduction of IAS is driven by increasing tourism, trade and limited institutional biosecurity capacity, including insufficient policies and quarantine facilities. These conditions provide a conducive environment for exotic species. Notable flora IAS are Ageratina adenophora, Chromolaena odorata, Eichhornia crassipes, Lantana camara, and Mikania micrantha. Specifically, C odorata, E crassipes, L camara and micrantha are listed among the world’s worst IAS. Tomato leaf miner (Tuta absoluta) and Fall armyworm (Spodoptera frugiperda) harm crops, and giant African snail (Achatina fulica) spoils vegetables.
The economic cost of managing IAS, such as Tilapia in water bodies, water hyacinth in the Fewa Lake, and Mimosa diplotricha in Jhapa’s community forests, is substantial, requiring extensive resources. However, the ecological, evolutionary and economic impacts of IAS remain under-studied, with a lack of evidence-based management strategies. While physical removal is common, bio-controls have yet to be formally implemented.
Nation-wide surveys, standardized guidelines, policy-advocacy and community awareness are warranted to address IAS.
IAS pose a silent threat, eroding biodiversity and economic stability globally. While developed nations combat established invaders, countries like Nepal face escalating risks due to weak biosecurity defenses and increasing climate change concerns. Proactive measures including stronger policies, scientific research and global cooperation are essential to mitigate these growing perils. Without urgent action, the ecological and economic consequences will be irreversible.
As Wilson’s call to action reminds us, we must reconsider our role as biodiversity stewards and safeguard ecosystems for future generations. Addressing the critical challenges from IAS requires proactive policies, enhanced cross-cutting research and stronger multi-stakeholder engagement to prevent further damage to the nation’s rich biodiversity.
The author is a biological scientist
