Climate change may wipe out Marula and Knobthorn, two tree species in Eswatini

Climate change may wipe out Marula and Knobthorn, two tree species in Eswatini

Subject: Environment

Section: Climate Change

Context: Climate change may wipe out Eswatini’s 2 major savanna tree species: Study

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• Climate change may wipe out Marula and Knobthorn — two tree species in Eswatini — from their current ranges, according to a new study. These widely occurring and dominant southern African species are critical to the functioning of lowland savannas.
• Compared with other terrestrial biomes, tropical savannas face heightened risks from a rapidly changing climate, noted the study.
• A westward shift in the distributions of marula and knobthorntowards central Eswatini is anticipated based on projected climate scenarios from 2041 to 2070, the research added. Responses of these two keystone species to climate change may decouple them in future. Such changes in the habitat of keystone species are likely to have considerable cascading effects.
• Marula and knobthornshowed idiosyncratic responses across a range of climate conditions, with marula expanding beyond current ranges to make up for lost distributions, while knobthorn patches receded towards the core of their ranges, the study noted.
• This suggested that these trees may be losing suitable climates within current ranges. Marula showed evidence of tracking climate change by emerging in previously cooler and uncolonised areas. On the other hand, knobthorn is unlikely to do so. In addition, knobthorn’spatchy distributions were limited to a smaller geographic area — thus, any range loss can cause a local wipeout.
• Knobthorn was unable to establish outside of its core range and faced limitations like land use, terrain and soil properties and herbivory to occupying broader climatic ranges, the study found.
• Marula would unlikely persist in some of the region’s hottest areas, with regional temperature increases for Eswatini projected to be 4°C between 2041-2070 and 2071-2100. However, the species’ ability to disperse and recruit in newly suitable climates beyond current range distributions could counter these effects, the study added.
• Africa showed an average increase in warming of approximately 0.3°C per decade between 1991 and 2021, according to State of the Climate in Africa 2021. This was faster than the warming of 0.2°C per decade, which occurred between 1961 and 1990.

Marula tree:

• Marula tree (Sclerocaryabirrea) is a native tree species of Africa
• The Marula tree is found across various regions of Africa, including South Africa, Namibia, Botswana, Zimbabwe, Mozambique, and parts of West Africa. It is well-adapted to a range of habitats, from woodlands and savannahs to semi-arid areas.
• The Marula tree plays a vital role in the ecosystem. Its deep roots help stabilize soil and prevent erosion, especially in arid and semi-arid regions. The tree provides shade and shelter to various animal species, including birds, insects, and mammals. It also serves as a food source for several wildlife species, such as elephants, giraffes, baboons, and antelopes.
• One of the significant features of the Marula tree is its fruit, known as Marula fruit. The fruit is small, yellowish, and rich in vitaminC. The fruits are used to produce various products, including Marula oil, jams, juices, and alcoholic beverages such as Amarula.

Knobthorn tree:

• Knobthorn tree (Senegalianigrescens, formerly known as Acacia nigrescens) is a prominent tree species native to Africa.
• The Knobthorn tree is found in various regions of Africa, including South Africa, Namibia, Botswana, Zimbabwe, Mozambique, and parts of East Africa. It thrives in diverse habitats such as savannahs, woodlands, and dry scrublands.
• The Knobthorn tree is a medium-sized deciduous tree that can reach heights of up to 10-15 meters.
• It has a characteristic appearance with a dark, rough bark and large, swollen thorns or knobs along its branches. The tree also features feathery, compound leaves that provide a dense canopy
• Knobthorn tree has a symbiotic relationship with nitrogen-fixing bacteria in its root nodules. This allows it to convert atmospheric nitrogen into a usable form, enriching the soil with nitrogen and benefiting other plants in the vicinity.