Some of Nepal’s highest mountains are being scaled by some furtive climbers — invasive weeds.

Research out of the Feed the Future Innovation Lab for Integrated Pest Management and its partners at Tribhuvan University in Nepal shows that as extreme climatic events persist, invasive weeds spread higher and more rapidly.

The program uses satellite images to capture how invasive weeds have spread over past and current climate scenarios and along Nepal’s vastly different elevations. Of the seven weeds the project tracks, all but one have significantly spread over the past 30 years, with some increasing by at least 800 percent. 

Muni Muniappan, director of the IPM Innovation Lab, said that if no mitigation efforts are made, crop production, livelihoods, biodiversity, and food security in Nepal are at risk.

“Our projections help us understand what areas in Nepal are most vulnerable to invasion — and how we should plan to address these vulnerabilities,” he said. “Nepal is an ideal country to study how climate change impacts a variety of ecosystems differently because it hosts a wide range of biodiversity in a relatively small area, but that’s also why the country has so much at stake. We know that if we are going to feed a rapidly growing world, these constraints to land and production growth need to be addressed, and soon.”  

The global population is expected to reach 9 billion by 2050, which means that world food production will need to increase by 70 percent to 100 percent. Invasive species can adapt to climatic changes more rapidly than non-native species and outcompete for space and resources.

One of those invasive species is the weed Parthenium hysterophorus. The IPM Innovation Lab found that its range of spread will expand significantly in all regions of central Nepal. Many of these include protected areas, such as Langtang National Park, which fosters valuable biodiversity and is a popular ecotourism destination. The weed causes human health issues such as rashes and respiratory difficulty, taints livestock milk, and disrupts farmland.

Another invasive weed being tracked is Ageratina adenophora, which significantly reduces crop yields, displaces native plants, and affects the carrying capacity of grazing lands. The IPM Innovation Lab has predicted the weed will expand to much higher elevations in all but one region in central Nepal.

“As the global temperature warms, invasive weeds are climbing higher and higher up the mountains,” said Pramod Jha, professor emeritus at Tribhuvan University and one of the project leads. “All of the invasive weeds the program studies are originally subtropical and tropical in nature, and first invaded those habitats. Now they are gradually spreading to new habitats, like the mountains. This is especially concerning because the mountains of Nepal also house many of the country’s poorest communities. Invaded lands will impact their ability to grow food productively.”

One of those threatened food crops is finger millet, Nepal’s fourth most important crop. Remote mountain communities depend on finger millet — considered a “poor man’s crop” — because it can grow in rain-fed, subsistence farming conditions. Communities also rely on it as an important source of protein, fiber, calcium, and iron.

The IPM Innovation Lab measured that under future climate conditions, where invasive weeds will be more widespread, the suitable area of finger millet will shrink by 4 percent to 9 percent by 2050 and 9 percent to 10.5 percent by 2070. Communities that rely on this crop will be in even greater danger of food insecurity in the coming years.  

“Examining the nexus between climate change, land, and food security has been a long-held priority of the IPM Innovation Lab,” said Van Crowder, executive director of the Center for International Research, Education, and Development, which houses the IPM Innovation Lab, and a professor in the Department of Agricultural, Leadership, and Community Education in the College of Agriculture and Life Sciences. “Using evidence and data from this project in Nepal and others can help strategically guide farmer and stakeholder training to build capacity to address climate change in the field and ultimately build resilience against its impacts.”

Invasive species do not see country boundaries — spreading by wind, trade, and through other routes — but mitigating their movement in one country can significantly curb their spread to another. As the IPM Innovation Lab continues to track the spread of invasive weeds over valuable land in Nepal, the program not only alerts communities at risk of invasion but also recommends ecological management strategies to minimize the impact.

The IPM Innovation Lab is funded by the U.S. Agency for International Development. The Center for International Research, Education, and Development is part of Outreach and International Affairs.

Written by Sara Hendery

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