Helskloof aloe decline to be investigated
The park’s nursery and herbarium curator Pieter van Wyk says that the declining population might even be due to extensive overgrazing by livestock for the past 30 years in the Helskloof area or climate changes.
For most visitors driving over the Helskloof Pass on the South African side of the|Ai-|Ais/Richtersveld Transfrontier Park, the Helskloof aloes (Aloe pearsonii) are striking features in this rugged landscape, especially when in full bloom. This section of the park is their last haven; they occur nowhere else in the world.
Despite their seemingly large numbers there are no signs of seedlings. Historic photos also show that numbers have decreased dramatically over the years. Subsequently, baboon troops have been spotted breaking and feasting on the plants, leading to the initial perception that they might be responsible for the decline.
This has spurred on a long-term monitoring project to investigate this. “It is important to understand why this species is so abundant in Helskloof if we wish to keep it that way,” says the park’s nursery and herbarium curator Pieter van Wyk. The project will take place over the next five years.
Already, van Wyk made some interesting casual observations. “At first I thought that the baboons’ behaviour is very destructive and might possibly cause a population collapse due to the scale of the breaking and foraging. After collecting more than 100 broken pieces for the nursery I made a discovery that changed my mind on the impact the baboons might have on the aloes.”
He found that in controlled conditions, approximately 70% of the collected pieces, mainly the crowns, were actually able to sprout roots and continue growing. The baboons only eat the inner trunk of the plant, which is not as bitter as the leaves, and leave the crown with leaves on the ground. Once it was discovered that the plants can propagate, the scenario changed slightly. Numbers might in fact be high because of the baboons as these plants are able to recruit despite the damage.
Van Wyk is now hoping to prove this through research. “In theory, if 50 pieces, for example, were broken from one plant and at least 10% re-root during winter, there should be five new plants,” he says. Van Wyk says that baboons also hardly ever forage on the same plant the following year as they harden and become shrubby as a protective measure.
Enclosures have been erected to monitor the plants, including adults and broken pieces. These experimental plots serve more than one purpose. While some aim to keep baboons away from the plants, others are meant to keep the community livestock away. Because this national park belongs to the local community, sheep, goats and cattle are allowed in the park. The monitoring will also include the dispersal of broken pieces to determine the impact of trampling and sprouting success. Adult plants will be monitored to establish their overall reaction to the damage.
For now, Van Wyk says that the declining population might even be due to extensive overgrazing by livestock for the past 30 years in the Helskloof area or climate changes. The lack of seedlings might be because of an unknown wasp larvae living on the seed, but all of these theories will be tested over the next couple of years.
Except for Aloe pearsonii, the unique micro-climate of Helskloof allows a number of endangered species to flourish. This includes the paradise lily (Amaryllis paradisicola).
