Catherine Nakalembe is describing the speed at which locusts devour plants. “You might have a whole lettuce in the evening and then come back in the morning to find it gone,” she says, recalling her recent attempts to grow vegetables in her garden in Kampala, Uganda.
Given that a single locust can consume a lettuce overnight, the impact of a whole swarm of them on crops – and on the farmers and communities dependent on those crops – can be devastating.
“A locust invasion can decimate the food supply of an entire population, particularly when they are in their infancy – the ‘hopper’ stage, when they are completely uncontrollable,” says Nakalembe. An assistant research professor and leader of the NASA Harvest Africa programme at the University of Maryland, her research focuses on agriculture and the use of satellite data in East Africa.
Locusts are an age-old problem, but a perfect storm of conditions this year has brought an enormous increase in numbers in countries such as Kenya, Ethiopia and Somalia. Unusually high rainfall in normally dry places, as well as cyclones in the Indian Ocean, allowed lakes to form in the deserts. This has encouraged vigorous locust breeding while nurturing more vegetation for them to feast on.
As conditions turn dry where they are feeding, locusts move on, flying with the wind and rain to more verdant pastures, devouring fresh vegetation as they go. The punishing impact on crops has implications for food security in a region already vulnerable to the impact of climate change. Moreover, it threatens to displace people and generate conflict in already insecure areas.
The current crisis is also due to new swarms breeding in, then moving on from, Yemen. Some swarms moved northwards to near the India-Pakistan border. Fortunately, those two areas had the weather on their side this year. An early and short monsoon somewhat tempered breeding. The two countries also worked together to throw massive resources at the problem, managing to establish a measure of control.
East Africa was less lucky and less well equipped. This is largely because locust storms are infrequent there. “West Africa experiences locust invasions every few years, so they have to have a whole range of defences, with teams dedicated to monitoring breeding areas and to providing a swift response with the support of cars, planes and equipment,” says Nakalembe.
In East Africa, however, locust invasions are rarer. This year has been the worst for 25 years and, in Kenya, for 70 years.
Keith Cressman, senior locust forecaster at the Food and Agriculture Organization (FAO) of the United Nations, says operations in the region have been upscaled, but it’s hard to cope with the enormity of the problem. “It’s a real challenge to maintain a structure, with the requisite level of training, experience and equipment, that can quickly respond to an invasion but also be sustained in the years in between invasions. We don’t have a good answer to that yet.”
In practical terms, the approach to tackling locust swarms is much the same as it always has been – try to predict where they will be, then use pesticides to tackle them promptly. And despite advances in satellite imaging, the data collection process remains distinctly low-tech. “There’s still no substitute for boots on the ground,” says Cressman. “By this, I mean a survey team in a four-wheel drive looking for green vegetation in the desert and checking for the presence of locusts.”
The difficulty of this task shouldn’t be underestimated. “Often they are checking flat plains, with no topography or landmarks for 300-400km. Some areas are also insecure and difficult to access, including northern Mali, Libya, Yemen, Darfur and Somalia.”
Advances in technology are, however, starting to make their efforts more precise. Drones with elastic launchers, which can travel hundreds of kilometres while mapping areas of greenery have been added to the defence arsenal. Then there’s the role of Cressman’s office, which guides the country teams using remote sensing imagery.
The way in which locust control forces communicate has also improved. “We used to send information by letter, and then telex and fax. Now it’s email and satellite,” Cressman says. Survey teams use a tablet connected to a satellite antenna called the eLocust3, which allows them to enter their observations – soil conditions, vegetation, rainfall and the presence of locusts – plus their geo-reference, in English, French or Arabic. “In less than a minute, this data goes from the middle of nowhere to the relevant national locust programme headquarters,” Cressman says.
The same standardised data, gathered across more than 50 countries, goes to his office. “I use it to predict patterns of breeding and migration, normally six weeks in advance,” he says.
Countries’ national locust programmes use this information to decide where to send surveyors, as well as teams with pesticides. Handheld sprayers can be used to tackle smaller infestations, but with large swarms, aerial spraying is the only option. The conditions need to be just right because the environmentally friendly pesticides used today need to be sprayed directly onto locusts’ backs. “Locust control is like fighting a war – you have a centralised command structure and teams on the field,” Cressman adds.
“Locust control is like fighting a war – you have a centralised command structure and teams on the field,” Keith Cressman, FAO
Locust Hub, part of the Africa Geoportal, is an open-source platform that the FAO has been developing with geographic information system specialist ESRI. Andrew Stauffer, director of the geoportal programme at ESRI, says: “Anybody can create a free account and then use our tools to work with and compare the data.” Users can overlay weather data, soil conditions, evaporation and crop types, as well as locust numbers. “The cool thing about it is that it’s not a snapshot – every time the FAO updates the data, you’re seeing things in real time.”
Nakalembe works to predict the damage that could be caused to crops by locust movements using satellite imagery, models and algorithms – advances that have leapt forward in recent years (see box, below). “You have to look at things like wind direction, whether there’s enough moisture in the soil for eggs to crack, and changes in vegetation and crop conditions compared with previous year,” she explains. This allows her team to examine, for example, the impact on greenness of an upcoming dry spell, which will affect locust activity.
On this front, though, this year’s weather presented yet another challenge: “The same rainfall that led to the locusts breeding and getting out of control has created a problem for remote sensing because the vegetation has been so much greener than average.” This makes it difficult to compare variation in greenery with previous years.
Nakalembe’s team are trying to find creative solutions to the problem, including asking contacts in affected areas to send close-up pictures of crop damage via WhatsApp. The plan is to overlay these on to cropland maps, many of which need updating.
“In a lot of developing countries there’s a gap in this area,” says Nakalembe. “But we have just finished a 2019 cropland map for Kenya, and we’ve also been making it more straightforward to complete conditions assessments. This helps insurance programmes and government response programmes anticipate when things will be bad and respond accordingly.”
Technology and large-scale operations aside, locusts remain a very human problem: livelihoods are destroyed by their presence. Farmers deal with many pests themselves but locusts involve specialist knowledge and equipment.
“The best thing communities and farmers can do is alert the national authorities whenever they see locusts,” advises Cressman . To help achieve this, the FAO has developed the eLocust3 system into a mobile phone app, which is integrated into the national monitoring system. The app asks for just a few key pieces of information, making it easy for everyone to use. A simple interface allows you, for example, to click on a picture of what kind of locust you see.
Getting such people-powered systems working, as well as reducing the spread of panic and fake news, relies on education and greater awareness, from farmers and communities to the highest levels of government. “We need people to know what locusts are, what they can and can’t do, how long they live and when they are most dangerous,” says Cressman.
Then there’s the unique challenge that 2020 has posed: the coronavirus pandemic. Nakalembe explains: “In a normal year, when everybody could travel and do what they wanted, the FAO would be training people and trying to build capacity at national agencies. In 2020, with lockdown, there have been all sorts of logistical issues in getting pesticide training teams to East Africa, so there isn’t an established workflow at institutions.”
Not enough is known yet about whether increasingly unpredictable weather patterns will create more favourable conditions for locusts in the coming years. But the central challenge remains that of capacity. How do you maintain a nimble and robust permanent infrastructure to tackle massive locust infestations in places where they may happen infrequently?
“It doesn’t matter how good the data is and what algorithms are being used – that means nothing if there isn’t an institution ready to own it and use it,” argues Nakalembe. “I hope this challenge will be fully addressed, because nothing can be done by just hoping for the best.”
“It doesn’t matter how good the data is and what algorithms are being used – it means nothing if there isn’t an institution ready to own it and use it” Catherine Nakalembe, NASA Harvest Africa
Advances in satellite technology, as well as the opening up of GIS data through initiatives such as ESRI’s geoportal programme and the non-profit Open Data Cube, have made the task of predicting locust swarms and crop damage more realistic.
The Group on Earth Observations (GEO) – a network of more than 100 national governments – have launched a global agricultural monitoring initiative (GEOGLAM), to produce and disseminate information to improve food security and support early warning responses to emergencies. It is a project to which NASA Harvest Africa’s Catherine Nakalembe contributes.
In July 2020, the GEO launched an international competition to design software to help policymakers balance the expected loss of productive land with the recovery of already degraded areas. Another GEO programme, Digital Earth Africa, includes open data for the entire continent of Africa (in collaboration with the Open Data Cube, FAO, UN World Food Programme and others). So far, it offers water observations from space, with crop monitoring maps in production.
For its part, RICS is developing the 6th edition of its Aerial Imagery & Earth Observation guidance, in consultation with experts including the Remote Sensing and Photogrammetry Society and the Association of Remotely Piloted Aircraft Systems.
RICS’ 2010 guidance on vertical aerial photography and digital imagery is used extensively by those procuring aerial imagery. The updated guidance will expand its remit to include drone imagery and sensors and earth observation imagery and data, emphasising the continuing relevance of traditional aerial imagery best practice. It is due to be launched in May 2021 at the GeoBusiness conference in London.