Eyes in the sky protect forests from ‘death by chocolate’

Some people swear it calms their nerves; others simply enjoy its rich unique flavour. Chocolate is a sweet treat popular across generations and, in its dark low-sugar variety, sought after even by health-conscious foodies. Demand for chocolate is rising globally, with Europe being the biggest consumer. In the UK, an average person consumes about 7kg of it per year. What chocolate lovers don’t realise is that their sweet tooth is contributing to the destruction of rainforests in many parts of Africa.

In Ghana, the world’s largest producer of cocoa, cultivation of the Theobroma cacao tree has been responsible for about one-quarter of historical deforestation. And the trend shows no signs of stopping.

According to Ethan Budiansky, director of environment at the World Cocoa Foundation, obsolete agriculture practices employed at many African farms lead to low productivity, which forces economically struggling cocoa farmers to encroach on rainforests.

While traditionally the Theobroma cacao plants were grown in complex agroforests under the shade of large rainforest trees, today, in many areas, farmers are switching to sun-loving cacao varieties grown in monocultures, which provide higher yields at the expense of the ecosystem.

A project led by the UK Space Agency aims to use satellite data to stop deforestation caused by cacao farming and help support farmers to maintain their farms, and thus their livelihoods, more sustainably.

“As part of the Forest 2020 project, we are developing a platform that could integrate data from various satellites, drones and planes to enable governments and university teams to see forest change and land-use change over time,” says Athene Gadsby, Forest 2020 programme manager.

The project partners hope to help the governments of Ghana and Côte d’Ivoire, as well as 32 global chocolate producers, to meet the goals of the Cocoa & Forest Initiative, which aims to achieve 100 per cent traceability of cocoa supply chains by 2022.

“Africa is an enormous continent with relatively weak infrastructure and institutional capacity to know what’s happening, especially in real time,” says Professor Mat Williams, chair of Global Change Ecology at the University of Edinburgh and academic lead for the Forest 2020 project. “Satellites are really important for monitoring these huge landscapes.”

‘We are developing a platform that could integrate data from satellites, drones and planes to enable governments... to see forest change and land use change over time.’

However, the researchers are facing challenges. While current satellite instruments are excellent at monitoring canopy coverage, they might not always be able to pick up exactly what’s underneath – the biomass of the trees, for instance, and any plants hidden by the canopy in the understorey layer of the forest, including, for example, cocoa being grown illegally in protected areas.

“Radar is particularly useful as it can, at longer wavelengths, penetrate the leaves and scatter off the branches,” says Williams. “The Japanese ALOS satellite has an L-band radar with a 24cm wavelength that scatters off the branches and stems about that size. At the University of Edinburgh we have shown that it can very effectively map biomass of woodland and savannahs. However, for monitoring of denser biomass in equatorial forest you need longer wavelengths that are not currently in space.”

The Forest 2020 team, led by London-headquartered company Ecometrica, will therefore supplement the satellite images with data from a lidar instrument flown on drones and planes over the areas of interest.

“Lidar instruments use pulses of laser light, which enables us to build a vertical profile of the forest to see how much of an understorey there actually is,” says Williams. “With lidar, you send many individual laser signals down and, while a lot of them will bounce back off the first level of canopy, some will get through the first layer of leaves and scatter off the next layer, and some will make it right through to the ground. With careful modelling we can recreate where the scattering elements are and whether there is an understorey or not.”

In April this year, Ecometrica announced it had delivered its landscape-level map to the Ghana Forestry Commission to help cocoa companies and authorities track cocoa supply chains and assess the impact of cocoa farming on protected areas.

Later this year, the company plans to conduct flights with a lidar-equipped aircraft that will help researchers improve the detail and accuracy of information provided by the platform.

“It’s possible that we will find patterns related to the way the particular understorey species like cocoa are structured,” Williams adds. “There is still research to understand the information content of the lidar data.”

Williams added that in the future, hyper­spectral lidar instruments could enable the scientists not only to see the understorey in the rainforest but also to deduce more information about its exact composition, including the plant species involved.

“With hyperspectral lidar we would not only get the return of the light but also the return wavelength of the scattered light, which might tell us about the diversity of the canopy,” says Williams. “But these instruments are still very much in development.”

According to Williams, warriors against deforestation will get a new powerful tool in the early 2020s in the form of the European Space Agency’s Earth Explorer 7 satellite, which is being designed specifically for biomass monitoring. It will fly a 70cm wavelength radar instrument, which, according to Williams, will have the ability to scatter off the large trunks typical of grown rainforest trees.

As Williams says, the goal of the current efforts is not to punish smallholder farmers who frequently struggle to make ends meet, but to help them find tools and strategies to make the best use of their landscape.

According to Budiansky, cocoa farming can have a positive effect on the environment and even contribute to reforestation if farmers are encouraged and supported to plant the traditional shade-loving varieties and develop agroforestry systems.

“In the Amazon, for example, cocoa has become a forest-positive tree, encouraging farmers to not only grow cocoa but also grow other native forest species as part of an agroforestry system,” Budiansky says.