Forestry Ink: Introduced, not invasive species

Columnist Jim Hilton writes about animals that are considered invasive

Jim Hilton

Observer Contributor

I am watching very closely the small patch of Spotted Knapweed that established near our place.

I have seen how invasive it can become and out-compete the native plants if left unchecked. Some of the worst examples of other invasive species have been rats on some islands, rabbits and camels in Australia, as well as goats and wild boars in many places. But have you heard of the African hippos in Colombia, South America? That’s right, a herd of 80 African hippopotamus living free in a river system, which increased from four that escaped from the Pablo Escobar zoo after the death of the famous drug lord in 1973.

According to a recent CBC radio program (Quirks and Quarks), “In a new study, published in the journal PNAS, the authors look at the effects large herbivores like these hippos have on their new homes. They found that even though these animals are considered pests, they do provide benefits that should not be overlooked.

Escobar’s hippos are just one of many large herbivores around the world that are considered invasive species. The dromedary camel, also called the Arabian camel, is considered an invasive species in Australia.

Erick Lundgren, a PhD student at the University of Technology Sydney and lead author on the study, points out that the earth used to be covered in large herbivores. These mega fauna like woolly mammoths and giant sloths were all hunted to extinction by humans 10,000 years ago. With the loss of those animals, we also lost their benefits to the ecosystems on our planet.

The researchers analyzed 72 large invasive species and compared their ecological traits to those of the native mega fauna in the area. In 64 per cent of cases, they found that the modern-day species were fitting into ecological niches that have been vacant for thousands of years. This can affect things like nutrient dispersal, permafrost melt, wildfire causation and wetland distribution.”

The Colombian hippos are similar to two now-extinct species — giant llamas and noto ungulates, which have been gone for thousands of years. The hippos’ size, diet and semi-aquatic behaviours allow them to spread nutrients from the land into the water column in a way that hasn’t been possible for over 10,000 years. The authors caution that by labelling all invasive species as inherently bad means that their benefits aren’t being studied, and they suggest using the term “introduced” instead of invasive.

I think there are many other African species that could have a favourable impact on the dry grasslands of Colombia and Venezuela. During my research in the llanos (eastern grasslands) of Colombia in the 1970s, we were using domestic cattle to test stocking rates on native and improved pastures, but in retrospect, there may be some wild animals like water buffalo, many antelope species and other exotics that may have done much better.

Research has shown that much greater productivity of some grasslands is possible with the addition of grazing animals than without them. The greater productivity seems to be due to moderate soil disturbance, nutrient recycling and a variety of animals that can exploit the many layers of a grazing system. There are no large populations of large grazing animals in South America compared to Africa, so some introduced species could improve the plant productivity, as well as provide a safeguard for some species that are facing extinction in their native habitat.

Jim Hilton is a professional agrologist and forester who has lived and worked in the Cariboo-Chilcotin for the past 40 years. Now retired, he volunteers his skills with community forests organizations.

READ MORE: Forestry Ink: Quesnel working on forest diversity

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