The Chain Reaction of Climate Change and Invasive Species Spread: Impacts, Realities, and Sustainable Solutions

Every year, Nepal’s average maximum temperature goes up by .056 degrees Celsius, evidence of a warming climate. Nepal has some of the world’s most variable terrain and fosters unique biodiverse hotspots – but much of this terrain is threatened by climate change. In fact, developing countries in general host many of the world’s existing biodiverse hotspots, in which communities are dependent on for food security and livelihoods. Climate change has the potential to degrade that biodiversity, leaving developing countries with the most to lose from its effects.  

Another factor related to climate change, in which the Feed the Future Innovation Lab for Integrated Pest Management (IPM Innovation Lab) focuses on, is its impact on invasive species spread.   

The spread of invasive alien species (IAS), including animals, plants, or organisms that are introduced outside of their native range, is compounded by climate change. The extreme climatic events that are brought on by climate change, such as floods and droughts, open new entry points for IAS introduction. IAS tend to be flexible and responsive to new environments with few natural enemies to push them out, which is why native species are so easily diminished by their spread. Non-native species use changing climatic patterns to their advantage, capturing large shares of nutrients brought on by early blooming.  

The IPM Innovation Lab has worked in over 30 countries over the last 25 years, with a major focus on applying sustainable, integrated pest management (IPM) solutions to curb the threat of invasive species. This includes an intervention to abate the spread of the invasive papaya mealybug that saved India up to $1.4 billion in 2014 and a biocontrol management program for the invasive fall armyworm, featured in the Chicago Council on Global Affairs blog series in February.  

Currently, invasive species cost the world trillions of dollars annually. Without the infrastructure to combat those threats, the developing world is most at risk. As climate change persists, the IPM Innovation Lab is implementing a number of methods and techniques – considerate of social, economic, and environmental impacts – aimed at diminishing the chain reaction between climate change and invasive species spread, thus, protecting food security and the developing world’s most valuable resources.  

Monitoring the Spread of Invasive Species 

Tuta absoluta 

One of the fundamental aspects of mitigating the spread of invasive species is tracking their movement. By monitoring the spread of pests, the IPM Innovation Lab can sound early warnings to countries at risk of invasion. Currently, the project is monitoring the global spread of Tuta absoluta, a pest with the potential to devour 100 percent of tomato crops. After accidentally being introduced to Europe in 2006, the pest crossed the Mediterranean into Africa and Asia. It caused what became known as a “tomato emergency” in Nigeria, and is at risk of entering the United States, threatening the country’s billion-dollar tomato industry.   

The Tuta modeling project, led by Abhijin Adiga, a researcher at the Biocomplexity Institute at the University of Virginia, found that the pest’s mode of spread is predominately through human-mediated tomato shipments. The models indicate that production areas close to urban centers receiving imports from domestic and international regions are highly vulnerable to infestations of the pest. Due to global increases in trade, the models have predicted that it’s possible for the pest to spread domestically throughout a single country within two to four years of introduction.  

Muniappan said that in order to continue to curb the pest’s movement from country to country, policy that considers climate change scenarios is key.  

“Knowing that this pest is introduced predominately by humans highlights its seriousness,” he said. “IAS that have perhaps failed on their own to move into new places in the past may have future success in doing so because climate change is opening new pathways.”  

With this vulnerability in mind, the IPM Innovation Lab is working to introduce stricter quarantine regulations that aim to keep pests like Tuta absoluta entering so easily by way of trade.  

Additionally, with the knowledge of where and when Tuta absoluta will arrive and how quickly it will spread, the IPM Innovation Lab can conduct management and awareness workshops to help countries prepare for invasion. In 2012, for example, the team was the first to alert Senegal of the impending invasion of the tomato pest, helping the country and others to use pheromone traps to track its arrival. The program has hosted more than 30 workshops around the world focused on the pest. Since the tomato leafminer has no known major natural enemies, the program recommends trapping males to prevent procreation and application of neem oil, a bio-pesticide. 

Invasive Weeds 

Using satellite images, an IPM Innovation Lab team in Nepal – led by Pramod Jha, a professor at Tribhuvan University – has observed a 750 percent increase in spread of a single invasive weed, Mikania micrantha, over the last 30 years. This finding hits at the core of the project’s aim, which is to map the spread of invasive weeds throughout the country over the last 30 years, while analyzing how their spread is impacted by climate change, and namely how that affects land and biodiversity. With this knowledge, policymakers can make assumptions about the future spread of these weeds, and act to prevent their continued spread.   

Nepal is considered the fourth most vulnerable country to climate change in the world, with 118 ecosystems found within a short horizontal span. The IPM Innovation Lab project gives evidence for the country’s increasing vulnerability to climate change, demonstrating that a warming climate encourages the rampant growth of invasive weeds and their ability to climb to higher elevations. The project is generating distribution maps of seven invasive plant species in addition to Mikania micrantha including Ipomea carnea, Lantana camara, Chromolaena odorata, Parthenium hysterophorus, Ageratina adenophora, Eichhornea crassipes, which can have negative effects on people, animals, and the environment in Nepal and beyond.  

Eichhornea crassipes, for example, also known as a water hyacinth, degrades water quality and invades rice paddies. Mikania micrantha outcompetes native plant species eaten by the endangered Greater One-horned Rhinoceros. Chromolaena odorata is known as one of the most destructive weeds in the world, causing major crop losses. 

“Climate change is creating more area suitable for invasive alien plant species in a mountainous country like Nepal,” said Jha. “Our assessment through use of satellite imageries revealed 168 to 750 percent increase in invasive plant species in the Chitwan Annapurna landscape with a 168 percent increase in area of Lantana camara, 234 percent of Chromolaena odorata, 309 percent of Parthenium hysterophorus, 425 percent of Ageratina adenophora, and 450 percent of Eichhornea crassipes from 1990 to 2018.”  

The invasive weeds, Jha said, are originally tropical in nature and thus initially invaded in the tropical bioclimatic zone of Nepal, or the lowland area. The invasive weeds have gradually spread from the lowland area to the mountains, however, due to climate change and increased transportation networks.  

Notably, the spread of these invasive weeds is being dramatically felt by Nepal’s communities.  

“Mostly the weeding is done in Nepal manually,” Jha said. “Thus, invasion of invasive weeds has increased weeding labor inputs in agriculture… Pastureland in tropical and subtropical zones have been dominated by invasive species. It has become cumbersome and expensive to manage these weeds and the pastureland is now becoming fallow land.” 

In addition to mapping the spread of invasive weeds, the project is also analyzing the negative impact of climate change on future land availability, as it contributes to the depletion of important food crops. The project projected, for example, that the availability of land for both buckwheat and finger millet, two highly nutritious cereal crops grown throughout Nepal, will both significantly shrink by 2050.  

Managing Parthenium Weed in East Africa  

In East Africa, the IPM Innovation Lab is managing the invasive weed Parthenium hysterophorus. The team, led by Virginia State University (VSU) researcher Wondi Mersie, introduces biocontrol to curb its spread, releasing two natural insect enemies – Zygogramma bicolorata and Listronotus setosipennis. 

Managing Parthenium throughout the developing world is critical to improving food security and livelihoods throughout the region. In 2019, almost 20 million people across the region were food insecure, with the number increasing. Due to Parthenium’s ability to spread so rapidly, its presence dramatically reduces land value and increases weeding expenses. Replenishment of natural vegetation by releasing natural enemies improves conditions for livestock grazing and crop production.  

Parthenium is also a threat to human health. The weed causes major skin irritation as well as respiratory issues for those who are weeding, which is often women. In fact, Virginia Tech’s Women and Gender in International Development team and VSU conducted interviews with women smallholder farmers from the Oromo region of Ethiopia. Women farmers expressed specific challenges they and their families experience adapting to life with the spread of Parthenium, including how additional time required to manage Parthenium disproportionately impacts women, whose overall labor burden is substantially increased, and how Parthenium has reconfigured household livestock management, increasing women’s responsibilities in caring for cows, which are now brought in from the field to women’s space in the house-lot garden.  

The relationship between Parthenium’s spread and climate change is clear to farmers.  

“Farmers in this area are very strong and eager to work, but there is a lot of drought,” said Amelework Gudeta, one of the interviewed farmers. “In the past 3-4 years there is more drought.” 

The IPM Innovation Lab’s Parthenium biocontrol program has observed major improvements in both Ethiopia and Uganda with the releases of Zygogramma and Listronotus. Farmland has replenished where the damaging weed once thrived, and the natural enemies are showing signs of remaining, with life stages of the insects surviving the dry seasons and emerging from the soil in rainy seasons to feed on the weed. The insects are also spreading from the initial release sites to adjacent fields. 

However, according to Mersie, climate change remains a major barrier to eradicating the weed.  Studies show, he said, that parthenium gains a competitive advantage over pasture species at higher CO2 concentrations. If CO2 levels keep rising, Parthenium, too, will become more aggressive and will continue to displace many native species and biodiversity, and spread to more countries.  

“Parthenium could invade the whole of Sub-Saharan Africa,” Mersie said, “and aggravate the existing food deficit and environmental degradation. All indications show that the rising CO2 concentrations will confer many advantages to invasive plants like Parthenium over native plant species and food crops. From my own observation, it [Parthenium] is spreading rapidly and it is being reported from new places every year. This is especially the case in Africa.”  

The Future of Food Security, Climate Change, and Invasive Species 

As climate change becomes increasingly rampant in recent years, so does the influx of invasive species. A 2017 study shows that more than one-third of all invasive species introductions in the past 200 years occurred after 1970, with the rate of increase continuing to jump as globalization does too. The high cost of controlling invasive species, their ability to reduce crop quality and yields, and their growing impacts on people – especially farmer workloads – highlights the urgency to curb their threat, which could be significantly aided by curbing the threat of climate change.  

Combatting invasive species with sustainable innovation is key. Increasing excessive reliance on expired, chemical pesticides to control invasions, paired with the developing world’s limited access to personal protective equipment, could heighten stressors already being felt by developing communities. IPM interventions addressing invasive species spread and other challenges show immense potential for bringing economic benefits to the developing world, while also protecting valuable resources.  

The IPM Innovation Lab is funded by the U.S. Agency for International Development and is housed at the Center for International Research, Education, and Development at Virginia Tech.