Warming temperatures, other climate change impacts may increase locust outbreaks

Global Locust Initiative connects insect management and research

Even when the Tempe campus is quiet and classes are out of session, there is something alive and buzzing deep within the Life Sciences building at Arizona State University. Locusts chew, crawl and stretch their wings in a laboratory managed by the Global Locust Initiative, part of the Julie Ann Wrigley Global Futures Laboratory. The initiative is dedicated to locust research and management and the improvement of human livelihoods. Arianne Cease and Rick Overson, directors of the Global Locust Initiative, discuss locust outcomes in the face of climate change, the challenges of effective pest management and the potential of a university to enact creative solutions.

Arianne Cease is an associate professor in the School of Sustainability and School of Life Sciences, and director of the Global Locust Initiative. She is a sustainability scientist with a focus on the ecology and physiology of organisms in coupled natural and human systems. Her research involves transdisciplinary approaches to understanding how humanplant-insect interactions affect the sustainability of agricultural systems, including lab and field studies.

Rick Overson is a research scientist with the School of Sustainability and co-director of ASU’s Global Locust Initiative. At the Global Locust Initiative, he coordinates with stakeholders around the world to more sustainably manage grasshopper and locust outbreaks. His research seeks to understand the mechanisms that produce and maintain variation both within and between species, and how this variation ultimately affects the evolution of natural populations.

Let’s start simple: What exactly is a locust and how is it different from a grasshopper?

Overson: I’m glad you asked. As a kid growing up in Chandler I thought cicadas were locusts, and that was incorrect. So I’m happy to set the record straight for that younger version of myself.

Locusts are a very small set of special grasshoppers. There are thousands of species of grasshoppers. Depending on who you ask, there are around 19 of them that are considered locusts. They have a crazy ability that’s hidden in their genomes to respond to their environment in this dramatic way that leads to management implications.

As they’re growing, if it’s dry and resources aren’t widely available, they look and act like a normal grasshopper. But when those “times of plenty” come, they sense one another’s presence, and then they transition to totally different phenotypes. They change color, they change behavior, they become attracted to one another and they march across the ground in coordinated formations. If these conditions persist, that’s when you start getting coordinated flights together. This is when you see swarming that can break out on continental scales.

So essentially, a locust is a special type of grasshopper with quirks and idiosyncrasies of its behavior and its brain and its evolutionary history. Under different circumstances, these things would just be kind of a fascinating, evolutionary curiosity. But when locusts are reacting to their environment this way, it leads to massive, meteorological-scale events that need to be managed by dozens of countries at a time.

Arizona, and the overall United States, doesn’t have a locust population. Why study locusts here at ASU?

Cease: A lot of people here in the U.S. may not have exposure to them. They may have read about them in the Bible or the Quran, they’re featured in many religious texts. And when you look at these texts, they’re portrayed in a horrifying manner — for good reason. Locusts can be hugely devastating to food security. They still pose a major problem to many places around the world.

I think it’s important to note that there is no “extant” species in the U.S. That doesn’t mean we’ve never had locusts here. We had the Rocky Mountain locust, and they mysteriously went extinct in the early 1900s. So this is an issue that we have seen here, we may see it again in the future.

How ASU comes into this: I was a Peace Corps volunteer in Senegal, West Africa, and I arrived at the end of the last major desert locust upsurge. Seeing the long-term impacts that they have on livelihoods really compelled me to study them. Once I started trying to understand their biology and ecology, I quickly realized the strong connections between land use and cover change. I saw how locusts are governed and how that impacts development of locust outbreaks and impacts on food security. I thought that was a really important topic to study. Luckily, ASU President Michael Crow agreed.

As a university, we’re able to fill in a lot of gaps that other organizations may not have the flexibility to fill. We have the ability to grow our knowledge and apply that knowledge to make a real difference in communities. This kind of impact-driven work is a natural fit for ASU.

Overson: On the topic of seeing locusts here in Arizona, there is a climate change angle at play here too. There is the Central American locust that outbreaks regularly in Mexico. Our collaborators in Mexico have been modeling future outbreaks, and that species is getting closer and closer to the U.S. border. As climate change is driving hotter temperatures, the locusts are attracted to the heat. It may not be much longer that we can say we don’t have an extant species here in the U.S.

Cease: Insects are generally ectothermic, which means that they gain their heat from their environment. They don’t produce a lot of internal metabolic heat, and increasing temperatures generally means that they develop faster. For some insects, rising temperatures like we’ve seen are going to push them out of their thermal limit. But for a lot of insects, if they can change their behavior patterns, it can help them speed up their development. Sometimes that also leads to larger body size, sometimes smaller body size.

Primarily, heat allows them to go through their cycle faster. Generally, if they can do that, that means less predation when they’re young, and more opportunities to reproduce. And then, if they can have multiple generations in a year, that means they can generally get through those generations and have a faster population growth rate. Locusts tend to like it warm, and it’s certainly getting warmer.

What kind of damage can locusts cause?

Overson: When there isn’t an outbreak, the desert locust can cover an area of around 16 million square kilometers across roughly 30 countries. But during an outbreak, they can spread over 29 square kilometers and expand to parts of 60 countries. There are hundreds of millions of individuals in a swarm. Many swarms move across a continental scale, and they eat a ton.

Some of the estimates from the United Nations say that swarms can eat the same equivalent of food as 35,000 people. That can be absolutely devastating to food security.

Cease: I arrived in West Africa at the tail end of the desert locust upsurge in 2005. That upsurge caused about $2.5 billion in agricultural damage and cost about $450 million to control. That’s just putting the short-term devastation in terms of money. I think perhaps more poignant are the long-term impacts on livelihoods.

There have actually been relatively few studies looking at livelihood impacts, but there was one done in Mali studying the 1988 locust plague. They found that children born in plague years and villages impacted by locusts were much less likely to ever start school. The impact was worse for young women.

We think about these numbers in terms of food insecurity, and that is certainly a strong element that we have to consider. But locusts also have these long-term impacts, things we don’t always consider right away when we talk about locust outbreaks. A locust outbreak is truly life-altering in so many ways.

Locust management is incredibly multifaceted. What are some of the elements you have to consider?

Overson: I think in some ways, the actual insect part of locust outbreak management is kind of a red herring. People can fixate on the insect itself — how it moves, how it thinks, what it does — and then I think they don’t see it in the same way that they see other problems like climate change or like wildfire management. I get it; My background is in insect behavioral ecology. It’s easy to focus on the bugs. But locust management requires the same social, ecological, technological approach as other problems to move the needle of improvement.

Cease: On the locust level, each species of locust is a little bit unique. They evolved independently of one another and have different ecologies. But to Rick’s point, it goes beyond the bugs. For example, desert locust plagues can expand into up to 60 countries. That means looking at completely different ecosystems, cultural and political contexts. If there is political conflict in a region, locust management and monitoring is going to struggle. Each region is dealing with a different set of struggles in between these locust outbreaks that influence locust management.

Even during the recession time period between outbreaks, you still need to have coordinated, consistent efforts in place and ready to act when needed. That is really challenging for all of the same reasons it’s challenging to govern disease outbreaks.

There are a lot of similarities, actually, between disease outbreak efforts and locust management. When there’s an upsurge, it’s front of mind. It makes international news. People start research programs, international donors set up programs. But once the locust numbers wane, that problem is slowly forgotten.

It can be 20 or 60 years in between locust upsurges in a given region at any point in time. Sixty years might not feel like a lot of time, but in government time that is ages. Those programs that were established at the beginning of one upsurge to address the problem might be forgotten by the time the next locust upsurge comes around. The people who drove those solutions forward and saw the previous outbreak may be retired or no longer with us. The wisdom can be lost, both within the government and the communities affected.

That’s why it’s so critical to have a global network where we can exchange ideas and resources. We really have to work together, to stay connected. When the upsurge does happen in a given area, we have to do the work to make sure we aren’t starting from ground zero again.

The Global Locust Initiative is split into two primary pillars: a laboratory and a global network. How does this structure support the work you do?

Cease: The organization of the Global Locust Initiative allows us to have a space for advancing specific projects, but also for building and maintaining a broader network. You absolutely need to have both of those elements to succeed in tackling this issue. We have a variety of research projects, some of which are sponsored by entities like the National Science Foundation and the U.S. Department of Agriculture. That allows us to push forward on these different elements like nutritional ecology of locusts, understanding how they migrate long distance and how communities can use sustainable land-use practices to limit outbreaks.

We have a lot of strong partners we work with on these projects, and the network is crucial to communicate with other people working in this space.

Overson: I spend about half my time working with graduate students and researchers here to facilitate locust research. In the Life Sciences building at ASU, we have large facilities with walk-in environmental chambers. These chambers hold thousands of active locusts from around the world. That’s a lot of mouths to feed — I joke that it looks like a Jamba Juice with the amount of wheatgrass we grow for these locusts.

Through our work with locusts in the lab, we’re trying to understand their nutritional ecology and their physiology in ways that can translate to more sustainable management. The other piece to this work is that global network. I spend the other half of my time sharing information and research outcomes from not just our group, but the broad group of researchers who are also working on these themes. Mira Ries, who couldn’t join this conversation today, is our research project coordinator. She does a lot of the heavy lifting to engage our network through information sharing tools and online platforms.

One of our newer online platforms is HopperWiki, currently in beta mode. Through our work in the global network, it became apparent that there’s a lot of information needed to make decisions in this space. That information is either not available, hard to find or behind paywalls. The wiki is an effort to sort of democratize and aggregate and make that information more easily discoverable across our broad network.

What is the importance of including students in your work?

Overson: I think we offer a unique experience because on one hand, we’re — I say proudly — very nerdy. We explore fundamental nutritional biology on locusts and experimentation on insects to try to understand their biology better. But on the other hand, we’re engaging in real time with the stakeholder network that we manage. We’re working on multiple aspects of the social, ecological, technological interface. We combine so many different elements and strategies of problem solving.

ASU allows for undergraduates and graduate students to come into this space where they get this exposure to really gnarly problems. But they also get to see what it takes to work toward solving these problems.

Cease: For many reasons, I think this is a great opportunity for both ourselves and the students. A lot of students that do get engaged really want to have that sustainability applied component. They want to have direct connections with stakeholders, which is really exciting, because we have all those connections. We’re actively working with stakeholders that are facing these challenges every day.

I think that’s really, really empowering for newer professionals in this space. We also strive to support students to develop their independent questions and projects within the umbrella in which we work. And it benefits the work greatly to have students as core members of the team. They have so many creative insights, they offer perspectives that we can sometimes lose after looking at the same problem for so long. It sets us apart in a really special way from institutions that aren’t based in academia.

Our work being set in a university is unique too because it allows us to really expand on that creativity. We aren’t bound to one specific mandate, we aren’t confined to one silo. Universities allow for freedom in how we tackle a problem, how we apply solutions. And then on top of all of that, we recruit these amazing students to work with. The primary reason I chose to work with a university is that I wanted the freedom to think about a more holistic response that’s going to offer solutions for multiple outcomes.

I have deep respect for our colleagues at plant protection organizations who have the mandate and challenging responsibility to manage plant pests and pathogens in real time. Working closely with these organizations allows us to support their efforts for developing more systems-oriented management approaches and decreasing reliance on reactive management with chemical pesticides.

Locust outbreaks pose a large threat to human health and wellness. As we face unprecedented times for our planet, what does the future of locust management look like?

Overson: The solution is not to kill all locusts. I’ll own it — I’m a bleeding heart entomologist. I love bugs. But looking beyond my personal fondness for these bugs, locusts are kind of analogous to wildfire. They can be devastating, but they play a role in ecological systems. We can’t and shouldn’t completely eliminate wildfire, and we can’t and shouldn’t completely eliminate locusts. They need to be responsibly managed.

The dials that we’re turning with climate change are going to make that management even more challenging. Species ranges are going to move in unpredictable ways, and the frequency and duration of outbreaks are going to change in unpredictable ways.

One of the best things we can do is build these support and information sharing structures. Concurrently, we need to increase our capacity to make early predictions of where these outbreaks are going to happen. From there, we can use strategic strikes where we can use less pesticides while still decreasing the scale of the impact. In an ideal world, we could even use biopesticides, which are much safer for humans in the environment.

Something I’ve noticed in my work these last few years: I think there is a level of arrogance about the locust issue. “We put a man on the moon, but we’re still dealing with bugs in the sky?” We need to get past that hubris and engage in careful capacity building across borders to move to a better future for locusts management.

Cease: I’ve heard all kinds of “easy” solutions: lasers on planes, big nets. There is a reason we are still struggling to solve this problem. These swarms can be the size of Manhattan or larger. Try putting a living, breathing, moving Manhattan in a net. It’s a complex issue that requires a complex approach.

The direction we’re going is increased locust outbreaks, and certainly an increased unpredictability of them. But it’s not all doom and gloom. I think it’s important to take a step back and listen to each other. There may not be one perfect, flashy, one size solution that will just solve the issue. For issues like this, there rarely is. Understanding the full view of the problem will lead to a more complete picture. Holistic understanding leads to holistic solutions.