How should we react if a food and fodder plant is called an invasive species?

The invasive prickly pear cactus

By Prof. Dr. Willem VAN COTTHEM (Ghent University, Belgium)

Opuntia ficus-indica (L.) Mill., also known as the Indian fig opuntia or Barbary fig, is commonly referred to as “the prickly pear cactus”. It is an evergreen, cold-tolerant, dense, massive, and tangled, trunk-forming cactus that can grow up to 15 ft (5 m) in height. It is segmented and can be found in arid and semi-arid regions, possibly native to Mexico, but now domesticated in all continents.

The cactus grows with flat, disk-like, edible paddles, which are typically armed with sharp, hard spines and small, hair-like, easily detached (washed off) prickles (glochids). However, there is also a variety (var. inermis) found on all continents that lacks hard spines and is therefore easier to handle.

This plant is commercially grown as a fruit crop for its large, sweet fruits (the tunas, beles, ficudinnia) and for its young green paddles (cladodes), called nopales. Mexican natives have been using this food for thousands of years.

Food and culinary uses

The young paddles (nopales) are sliced into strips and eaten with eggs or chili peppers (huevos and tacos) and are very popular dishes in Mexican cuisine.

Fruits are eaten all over the world either raw (after washing or burning off the glochids) or as jam and jelly.

The fresh fruit pulp contains vitamin C and betalain pigments with antioxidant properties. Consumption of prickly pear fruit decreases oxidative damage and improves the antioxidant status in healthy humans.

Extracts of this plant are used in the pharmaceutical and operational food industries. In some countries, people use it to make non-alcoholic punches (aguas frescas), or alcoholic wines and liqueurs.

Fodder (https://youtu.be/xsnBWBIek2g)

Cattle do not eat the paddles due to their sharp spines. However, these spines can be burned off. The pads, also known as paddles, of certain cactus varieties, particularly the spineless ones (var. inermis) are a valuable supplement for livestock in the drylands. They have a high moisture content and food value, making them a useful feed source. Dried pads or strips of cactus can be ground to make cactus meal, which is also used as a feed supplement.

Medicinal uses (https://www.drugs.com/npp/prickly-pear.html)

Prickly pears have various medicinal uses. They were used by sailors to prevent scurvy and their fruits are still used as a dietary supplement to reduce oxidative stress or to increase low blood lipid levels. Fruits without seeds are used as a laxative. Opuntia, the genus of the prickly pear cactus, contains many alkaloids that have antispasmodic, diuretic and emollient properties. Its flowers are astringent and used to reduce bleeding and to treat gastrointestinal tract problems, especially diarrhea, and an enlarged prostate gland. An extract of the prickly pear plant has a moderate effect on reducing hangover symptoms by inhibiting the production of inflammatory mediators.

Dye production (https://en.wikipedia.org/wiki/Cochineal)

Cochineal red dye, used in food coloring and cosmetics, is produced by extracting carminic acid from a scale insect, called Dactylopius coccus, which lives on Opuntias.

Hedgerows  (cactus curtains)

Opuntia ficus-indica, a cactus species, forms dense, tangled, bushlike structures, used as barrier hedges, also known as hedgerows.  They are particularly used in drylands.

Binding material in adobe

The juice from cactus paddles and stems is commonly used as a binding and waterproof ingredient in adobe, a natural building material made from sand, clay, water, and fibrous or organic material, such as sticks, straw, and/or manure. The juice is added to earthen plaster to enhance its binding and waterproof properties.

Is this cactus a real pest ?

The prickly pear cactus, which is covered with spines, is generally considered as a noxious weed and an invasive pest species because its uncontrolled growth causes ecological damage. However, the question remains if this is also the case for its spineless variety (var. inermis).

Considering that “nopales” (young Opuntia pads) are commonly eaten as a vegetable in Mexico, Brazil, and other South American countries and that thousands of hectares are cultivated as “nopales plantations” in these regions, it becomes difficult to keep this spineless variety classified as a noxious invasive species. A real cactus industry has developed in these countries, seemingly without harming the local ecology.

As this cactus grows remarkably with a minimum of water, one may wonder if the introduction of the spineless variety, with all its positive characteristics and advantages listed above (food, fodder, medicinal uses, adobe, hedgerows, etc.), still has to be considered a factor causing ecological damage in desert-like environments.

Here is an interesting challenge: Would it be preferable to keep the mostly barren, non-cultivated soil uncovered and subject to erosion, or would it be better to use this spineless cactus variety to:

● Cover large parts of the barren soil with living, edible plants (see nopales);

● Grow hedgerows around small gardens;

● Create natural anti-erosion barriers;

● Offer juicy fodder to the cattle?

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