The Effects of Climate Change on the South African Quiver Tree

What are we talking about?

The Succulent Karoo biome in the Northern Cape province of South Africa is well known for its remarkable diversity (see Figure 1).
Estimates of the number of South African plants alive in the wild vary from less than 200 to 1202 individuals, to over 1500 individuals (1).
The famous big five animals found all over the continent of Africa: elephant, lion, rhino, leopard, and buffalo (2).

Learn more about current state of the Biodoversity of Africa here

The Quiver Tree’s home (see Figure 2) is the richest desert system in the world in terms of biodiversity, but also one which has been subject to intense changes in land use over the past century or so, has seen major political shifts, and is subject to extreme weather events and a harsh climate (3).
The arid western region of southern Africa, where the Quiver Trees occur, has become warmer and drier over the past 30 years (3) (see Figure 3).
South Africa is faced with prolonged droughts, along with problems of land transformation and deforestation. Even a few degrees increase in temperature and a few millimeters of decrease in rainfall could cause a decline in the biodiversity of plants and animals in the arid regions (4).
It is predicted that climate change will have a severe and negative affect on this region over the next 50 years (1), including the extinction of many plant species within the next 100 years (5).

Learn more about the Karoo Climate here.

Commonly called the Giant Quiver Tree, Aloa pillansii is a rare and endemic tree- succulent in the Family Aloaceae.
They can grow 3-9 meters high but has been known to reach heights of 12 meters (5).
The Quiver Tree has an average life span that is estimated between a hundred and two hundred and fifty years (6).
Succulents can survive long periods of drought conditions, due to the fact succulent plants has special water-storing tissue which makes part of the plant fleshy, and the Quiver tree has succulent leaf and stem (6).
The Quiver Tree is regarded as a 'keystone
species' in the arid Karoo, providing food for birds, and nesting and shelter sites for various birds that make holes in its trunk (7).
It is also a valuable source of water for animals in times of drought (7).
Their flowers produce a lot of nectar, which is a valuable source of food to various birds and bees playing the role of pollinator and provider (7) (see Figure 4)

Learn more about the Quiver tree here.

Today, the Quiver trees are threatened by agricultural expansion, overgrazing, and mining, as well as droughts and other climate changes, which are some of the major factors affecting the existence of Quiver trees (6).
The long-term survival of Aloe pillansii is threatened by drought, along with consumption by baboons, porcupines and other rodents, fungal infections and aphid infestations (3).
The Quiver tree is very sensitive to long term rainfall, and temperature and rainfall extremes, so future projected climate scenarios can make a huge impact on its survival (4) (see Figure 5 & 6).
Their growth rate is influenced by external environmental factors such as soil type, climate, diseases and grazing pressure (5).
The behavior of dying plants suggests that a decline in water balance, induced either by reducing water supply, higher temperatures, or both might be implicated (3).
It is predicted that climate change could cause a 50% reduction of the distribution range of Quiver Trees in the Northern Cape by 2050, as a consequence of the reduced rainfall and increased rainfall variability caused by climate change (5).

The Quiver Tree is protected in the Northern Cape under the Environmental Conservation Ordinance No. 19 of 1974. According to the Ordinance, no collection, cultivation, trade, export or import the Quiver Tree is allowed without a valid permit issued by the relevant conservation authority (7).

Monitoring the Quiver trees and using it as a climate change indicator is a continuing process and effort for the South African National Biodiversity Institute (4) (see Figure 7).
Workshops are held regularly with the Justice Training College on the complexities of biodiversity law. These have resulted in a dedicated environmental advocate in each province and a greater number of prosecutors across the country tackling environmental offences (8).

Duncan, J., Hoffman, T., Rohde, R., Powell, E., & Hendricks, H. (2006). Long-term population changes in the Giant Quiver Tree, Aloe pillansii in the Richtersveld, South Africa. Plant Ecology, 185(1), 73-84.
https://www.brandsouthafrica.com/tourism-south-africa/south-africa-animals/south-africas-wildlife-wonders. Website accessed March 2020.
https://conservationaction.co.za/media-articles/protecting-south-africas-biodiversity/. Website accessed March 2020.
Guo, D., Guo, R., Cui, Y. H., Midgley, G. F., Altwegg, R., & Thiart, C. (2011). Climate change impact on quiver trees in arid namibia and south africa. Climate Change-Geophysical Foundations and Ecological Effects, InTech, 323-342.
Guo, D., Arnolds, J. L., Midgley, G. F., & Foden, W. B. (2016). Conservation of Quiver trees in Namibia and South Africa under a changing climate. Journal of Geoscience and Environment Protection, 4(7), 1-8.
Midgley, G. F., Altwegg, R., Guo, D., & Merow, C. (2009). Are quiver trees a sentinel for climate change in arid southern Africa. Cape Town: The South African National Biodiversity Institute.Powell, E. (2005). Can the plunder of quiver trees be controlled?. Veld and Flora, 91(2), 70.
Myers, J., Young, T., Galloway, M., Manyike, P., & Tucker, T. (2011). Responding to climate change in southern Africa–the role of research. South African Medical Journal, 101(11), 820-822.
Powell, E. (2005). Can the plunder of quiver trees be controlled?. Veld and Flora, 91(2), 70.