Climate Change Threatens Steep-Slope Agriculture

A unique agri­cul­tural her­itage is being put at risk by cli­mate change in many coun­tries world­wide.

Steep-slope fields and crops are endan­gered more than other agri­cul­tural areas by water scarcity and increas­ing deser­ti­fi­ca­tion.

A new study pub­lished in Nature Food shows how the effects of cur­rent vol­umes of green­house gas emis­sions over time will sig­nif­i­cantly reduce or even end farm­ing tra­di­tions, many of which are deeply ingrained in the iden­tity of nations.

According to the authors of the research, steep-slope agri­cul­ture yields account for only 5.6 per­cent of the global agri­cul­tural out­put.

“But its his­tor­i­cal and land­scape value far exceeds those num­bers,” Paolo Tarolli, a land envi­ron­ment agri­cul­ture pro­fes­sor at the University of Padua, told Olive Oil Times.

According to the researchers, steep-slope field agri­cul­ture is prac­ticed on every con­ti­nent except Antarctica.

Most of the world’s steep-slope fields are located in moun­tain­ous regions. The largest con­cen­tra­tions are found in Central America, the Mediterranean basin, the East African Rift val­ley and China.

However, steep-slope field agri­cul­ture is prac­ticed in the Himalayas, Andes, Alps and Atlas Mountains of North Africa too. Farmers in the Philippines, Japan, New Zealand and Madagascar also employ the prac­tice.

“For exam­ple, think about the tra­di­tional Honghe Hani rice ter­races in Yunnan, China, where Hani peo­ple have farmed the ter­races for over 1,300 years,” Tarolli said. ​“There, not only 48 dif­fer­ent vari­eties of rice are grown, but the unique envi­ron­ment is also a pro­fi­cient habi­tat for ani­mals such as cat­tle, ducks or fish.”

Many olive groves also have thrived for cen­turies through­out the Mediterranean basin in steep-slope fields, mostly on ter­raced land.

“These areas are char­ac­ter­ized by a series of unique chal­lenges to farm­ing given that heavy mech­a­niza­tion is not fea­si­ble and main­tain­ing the soil requires spe­cial mea­sures,” Tarolli said. ​“It is highly frag­ile farm­ing land which is more exposed to cli­mate change.”

Among the chal­lenges for all types of agri­cul­ture, but espe­cially steep-slope farm­ing, are the grow­ing risks due to extreme weather events, such as sud­den tor­ren­tial rain­fall.

“These kinds of events might pro­foundly affect those areas if they are not cor­rectly and fully man­aged,” Tarolli said.

In coun­tries such as Italy, olive grow­ing on steep-slope ter­races is a tra­di­tion that dates back to Ancient Rome. Plenty of the country’s vine­yards are also grown on steep-slope fields,

In the coun­try, char­ac­ter­ized by exten­sive moun­tain­ous areas, fruit and cit­rus orchards are grown on ter­races too.

“They are all areas with very spe­cific soil char­ac­ter­is­tics, bio­di­ver­sity and ecosys­tems,” Tarolli said.

Given their dis­tinct cul­tural and his­tor­i­cal pro­file, many steep-slope agri­cul­tural lands are included on var­i­ous cul­tural her­itage lists, such as the United Nations Educational, Scientific and Cultural Organization and the Food and Agriculture Organization (UNESCO).

The European Union-funded Olivero project also ana­lyzed the uncer­tain future of olive farm­ing on slopes and steep slopes.

The researchers found that these groves will be aban­doned grad­u­ally or trans­formed into nature con­ser­va­tion areas. Still, many oth­ers will imple­ment drip irri­ga­tion tech­niques to enhance the pro­duc­tion of the olive trees, while oth­ers will increase their income by turn­ing to other activ­i­ties.

However, the risks iden­ti­fied by the Olivero researchers mainly were lim­ited to high pro­duc­tion costs, the exo­dus of younger farm­ers and soil ero­sion.

The research added a new layer to the threat­ened future of those groves. Scientists have designed a dynamic global map to high­light the chang­ing steep slope farm­ing areas for present-day (1980 to 2016) and future (2071 to 2100) sce­nar­ios.

In the cur­rent con­di­tions, steep-slope agri­cul­ture is mainly found in tem­per­ate (46 per­cent) and cold (28 per­cent) cli­mates. Seventeen per­cent are found in trop­i­cal regions, nine per­cent in arid areas and one per­cent in polar regions.

In the future sce­nario, if global green­house gas emis­sions con­tinue, and there is no active cur­tail­ing of cli­mate change, also known as sce­nario RCP8.5, those per­cent­ages are des­tined to change.

Steep-slope farm­ing will almost dou­ble in trop­i­cal areas (27 per­cent) and arid lands (16 per­cent). In com­par­i­son, it will more than halve in cold regions (down to 13 per­cent) and slightly decrease in tem­per­ate areas, down to 44 per­cent.

“The sharp expan­sion of the arid zones is partly due to cli­mate change in cold regions, with clear exam­ples found in Alpine and Continental Europe, coun­tries that sur­round the Black Sea, main­land Russia and main­land China, all of which host steep-slope agri­cul­ture,” the authors of the study wrote.

“Furthermore, future arid expan­sion is occur­ring in cur­rent tem­per­ate zones, with clear exam­ples found in the Mediterranean basin (for exam­ple, Italy and Morocco), China, and Central America, each of which are impor­tant hotspots of steep-slope agri­cul­ture,” they added.

“As water avail­abil­ity decreases in the future, water man­age­ment should focus on min­i­miz­ing the waste of water,” Tarolli said. ​“And more can be done. A strat­egy for steep-slope farm­ers, for instance, might be to store rain­fall in small local reser­voirs which will serve as a backup in case of drought as well as nur­ture local fauna and bio­di­ver­sity.”

“The mes­sage here is that if we do not enact mit­i­ga­tion and adap­ta­tion strate­gies, we do not only risk see­ing many lands become arid or even entirely degrade because of drought sever­ity and dura­tion, but we also risk los­ing tra­di­tions, cul­ture and land­scapes,” he con­cluded.

• Nature Food