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Novel remote sensing technology to map flowering plants

Scientists have created a flowering map for a semi-arid savannah site in Africa using a new remote sensing technology.

Researchers from Finland, Kenya, South Africa and Sudan, who created the map, say that despite significant rural populations of Africa getting income from bee keeping, data on the abundance and distribution of flowering melliferous plants — those that produce nectar and pollen collected by honey bees — are scarce.

_ “As more than 90 per cent of vegetable and fruits we eat are reliant on pollination, the availability of flowering plants and bees becomes a food security issue,”_ says Tobias Landmann, a co-author of the study and head of Geo-Information Unit of the Kenya-headquartered International Centre of Insect Physiology and Ecology.

The space-borne technology combines two mapping techniques — digital imaging and spectroscopy — that increase the ability to detect individually separate and distinct materials of interest for gathering key information towards identifying and classifying them, Landmann adds.

According to the study published in the Remote Sensing of Environmentjournal this month (1 September), researchers deployed a space-borne sensor on an aircraft, thus covering larger areas more effectively and systematically than ground surveys. They used the aircraft to help collect data on flowering plants in Mwingi County, eastern Kenya, during flowering seasons in February 2013 and January 2014. The researchers grouped flowering plants into brown leaves, crops, white forbs, white green and yellow green.

“All flowering plant groups together could be mapped with an overall accuracy of 83 per cent,” the researchers write in the journal.

Landmann tells SciDev.Net: “Previously farmers were drawing up floral calendars using field notes. This is tedious and highly subjective to errors. Farmers need floral calendars to know what to expect from the landscape in terms of bee hive productivity.”

According to its creators, the map is the first for a semi-arid savannah site in Africa.
Landmann adds that the new strategy for producing the map could be replicated in other parts of Africa because there are new and good spatial and spectral resolution space-borne remote sensing sensors available.
But he adds satellite signals would have to be validated using field observations within a particular area.

According to Landmann, the map could benefit agricultural extension officers, decision makers and beekeepers.

“Many beekeepers in rural Africa are dependent on products from bee keeping such as propolis, honey and wax [for] livelihoods strategy,” says Landmann. “For instance, in Kenya up to 25 per cent of farmers generate extra income from selling bee keeping products.”

He explains that practices such as deforestation remove flowering trees from the landscape, impeding bee productivity and ultimately livelihoods.

The project took one and a half years to complete as part of a 13 million euro (about US$14.7 million) project on bee health funded by the European Union.

Lusike Wasilwa, head of crop systems at the Kenya Agriculture Livestock Research Organisation, who was not involved in the study, says: “This will provide information on foraging of pollinators required by farmers to project impact on yields. It will also show the importance of pollinators.”

A Kenya-based consultant in research and agronomy, Peter Okoth, says the study is novel in the field of flower mapping, but adds that many interested actors might find it costly to use aircrafts for collecting data.

“More financial resources are therefore needed in order to extend the benefits of the mapping methodology beyond [the site] in Kenya,” he explains.

But Landmann says they intend to adapt and then apply a similar approach to satellite data to map larger areas without always having to rely on aircrafts, which is more expensive and tedious.