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Cactus - a key player in food security?
The cactus pear should be considered as a valuable asset, especially for food and livestock feed in dryland areas, said the Food and Agriculture Organization of the United Nations (FAO) in late November 2017.
During the recent intense drought in southern Madagascar, cacti proved to be a crucial supply of food, forage and water for local people and their animals, according to the FAO. The same area had once suffered a severe famine as the result of efforts to eradicate the plant, which some saw as a worthless, invasive species. It was quickly reintroduced.
While most cacti are inedible, the Opuntia species has much to offer, especially if treated like a crop rather than a weed run wild. Today, the agriculturally relevant Opuntia ficus-indica subspecies - whose spines have been bred-out but return after stress events - is naturalised in 26 countries beyond its native range. Its hardy persistence makes it both a useful food of last resort and an integral part of sustainable agricultural and livestock systems.
The need for resilience boosts cactus cultivation
Cactus pear cultivation is slowly catching on, boosted by the growing need for resilience in the face of drought, degraded soils and higher temperatures, FAO reported. It has a long tradition in its native Mexico, where yearly per capita consumption of nopalitos - the tasty young pads, known as cladodes - is 6.4 kilogrammes.
Opuntias are grown on small farms and harvested in the wild on more than 3 million hectares; increasingly they are grown using drip irrigation techniques on smallholder farms as a primary or supplemental crop.
Today, Brazil is home to more than 500,000 hectares of cactus plantations aimed to provide forage. The plant is also commonly grown on farms in North Africa, and Ethiopia's Tigray region has around 360,000 hectares of which half are managed.
Cactus stores water – a valuable asset in times of drought
The cactus pear's ability to thrive in arid and dry climates makes it a key player in food security. Apart from providing food, cactus stores water in its pads, thus providing a botanical well that can provide up to 180 tonnes of water per hectare - enough to sustain five adult cows, a substantial increase over typical rangeland productivity. In times of drought, livestock survival rate has been far higher on farms with cactus plantations.
Yields of commercially grown Opuntia vary substantially depending on the place, the cultivar and the growing technique. Harvesting more than 20 tonnes of fruit per hectare is common in Israel, Italy and where irrigation is used in Mexico - a few cases of 50- tonne yields have been reported - but output is lower in most arid and rainfall-dependent locations.
The cactus pear's biological trick is a special kind of photosynthesis - crassulacean acid metabolism - that allows the plant to take in water during the night. Still, there are limits. Below-freezing temperature causes irreversible damage to pads and fruit. And while the O. ficusindica can usually survive exposure to temperatures up to 66 degrees Celsius, its photosynthesis starts to slow above 30 degrees, which is why they are not often found in the Sahel or Mojave deserts.
More information: Crop Ecology, Cultivation and Uses of Cactus Pear (FAO, ICARDA)