The Giant quiver tree (Aloe pilansii)
is classified as critically endangered, and its distribution occurs only in a narrow band. A serious decline in the population has reduced the numbers to less than 200 individuals. There is no recruitment and the older plants are dying. Recent surveys suggest that there has been very little successful reproduction in the last 100 years. Many of the older trees are dying, indicating that the population does not appear to be naturally regenerating. Similar declines in population regeneration in sister species Aloe dichotoma
have been attributed to climate change and it is very likely that the bastard quiver tree is being affected similarly. These effects are worsened by the removal of plants by collectors, as well as through herbivory by baboon, porcupines, rock rabbits and livestock, which also trample young plants.
The species is threatened by mining (Rosh Pinah) in Namibia, damaged from blasting and chemicals. The species is also threatened by goats (browsing and trampling) in the Richtersveld at Cornell’s Kop, at Stinkfontein and Basterfontein. Due to overgrazing by goats, all cover has been lost and seedlings are not able to survive exposure to full sun and heat.
In the Richtersveld, the roughly 100 ha Cornell's Kop is home to a population. There are currently 75 individuals alive at this site. Of these, 44% are seedlings, 4% are juveniles and 52% are adults, taller than 3 m.
Since 1937 an average of 1.4% of the smaller juvenile plants up to 3 m in height has died annually. At this rate all the remaining 39 plants on Cornell's Kop in this size class will be dead in 71 years. The loss of plants in the 1-3 m size classes can be explained by several factors, including animal damage. Annual growth rates decrease as plants age. Plants up to 1 m in height grow at 42.5 mm/year, while plants 1-3 m and those taller than 3 m grow at 31.0 and 16.4 mm/year.
The relatively high proportion of seedlings suggests that conditions have recently been good for recruitment at this site. But the loss of six seedlings from the population in the last 5 years, probably due to grazing, suggests that without intervention this species will not survive on Cornell's Kop.