By Sharon Atieno
To understand the extent and intensity of global anthropogenic climate change a vast number of continuous, precise and accurate measurements are required. Some of the data are acquired from satellites, which allow observations at larger scales but these data need to be validated with ground measurements.
There was a critical knowledge gap regarding the temperatures being used to model climate change and disease outbreaks within agricultural production systems in East Africa as there were no sites where land surface temperature is observed simultaneously on the ground and with satellites.
In the vast 13,000 hectares of pristine, semi- arid rangeland belonging to the International Livestock Research Institute (ILRI) at the Kapiti Research Station, lies East Africa’s first land surface temperature validation suite.
Funding provided by the UK Space Agency to scientists from Kings College London and ILRI’s Mazingira Centre led to the installation of this international standard land-surface temperature validation suite. The suite consists of four towers up to 30 metres tall containing different radiometers (including NASA- engineered ones) and digital cameras to monitor land surface temperatures as well as cloud and vegetation cover.
“The instruments that are mounted to the towers monitor the surface temperature continuously. They ‘see’ a much smaller area (compared to satellite) and can thus be specific for grass cover, bare ground, shrubs, and trees. Such data can be used to calibrate and validate satellite measurements” said Dr. Lutz Merbold, ILRI’s Principal Scientist, head of Mazingira Centre.
The land surface temperature validation suite is also being used to help predict pest outbreaks as part of the Pest Risk Information Service (PRISE). PRISE uses a combination of earth observation technology, satellite positioning, and plant – pest lifecycle to anticipate and prepare for potential pest outbreaks in agricultural systems.
“At the end of the day, such land surface temperature measurements across a wide area are important for models that can be able to predict pest outbreaks. The better the data that goes into the models the better the predictions. So far very little of such ground validation data is available for Africa and that’s why we have this unique experimental infrastructure in Kapiti,” says Dr. Fava Francesco, ILRI’s senior scientist and head of the Drylands Innovations team.
“Eventually if models for pest outbreaks are improved due to better input data – including accurate land surface temperature – farmers will be informed in advance and be prepared for potential pest outbreaks in crops,” adds Dr. Merbold.
In addition, Kapiti, through a collaboration with University of Milano-Bicocca and Mazingira Centre, has installed another tower mounting a sophisticated instrument (unique in Africa) that is able to measure continuously Sun-Induced Fluorescence (SIF), a physical measure related to plant photosynthesis. This is an indicator of the functioning and health of the vegetation.
“SIF measurements are the last frontier of satellite remote sensing technologies for vegetation monitoring and the European Space Agency (ESA) is about to launch a dedicated satellite mission to measure SIF from space”, explains Dr. Fava.
“New indicators such as SIF would allow better understanding climate change impacts on rangeland and crops and early detecting stress conditions, allowing farmers and livestock keepers to react quickly and avoid major crop or livestock losses.”
The data set from these towers will be made available in the course of the year and will assist in evidence-based decision making of what agriculture could look like in the future.
Kapiti research station and a neighboring large-scale dryland agricultural area house so-called eddy covariance towers which researchers are using to measure greenhouse gas exchange between the land surface and the atmosphere.
“We can see how much carbon dioxide is taken up by the vegetation due to photosynthesis and also how much carbon dioxide is released to the atmosphere from plants and soils due to respiration – each life forms breathes (plants, microbes in the soil, animals) and thus contribute to carbon dioxide emissions,” Dr.Sonja Leitner, scientist within ILRI’s Mazingira Centre.
“Simultaneously, large animals such as cattle emit methane through belching. Ruminants have a different digestion system which include archae in their gut and allow them to digest plant material and produce protein that can be consumed by human. During this process methane another potent greenhouse gas is released which we can measure with the eddy covariance towers.”
Dr. Merbold says that with the eddy covariance towers: “We can observe which system is the most efficient in terms of providing food/feed to humans/animals and what their environmental footprint is.”
According to Dr. Fava, these observations will be also critical in understanding how individual ecosystems contribute to or compensate for climate change.
“Gathering this data is standard in developed countries but rarely achieved in the developing world. Until now, only eleven ‘flux towers’ are running on the African continent, each located in different ecosystems in southern or western Africa,” he notes.
Dr. Merbold says that the need to manage agroecosystem and make it as sustainable as possible can be achieved by emitting as little as possible of greenhouse gases per kg of product (milk, meat, protein) a system produces.
“Since there is hardly any data on both production and greenhouse gas emissions from rangelands we are doing this in Kapiti and at the nearby agricultural farm. With this we can show with real data which system is more efficient,” he says. “On the long-term we can also show which system is more resilient to climatic extremes such as drought or floods.”