Conditions of essential desert plants

Climate change effects on desert ecosystems: A case study on the keystone species of the Namib Desert Welwitschia mirabilis

By Pierluigi Bombi, Daniele Salvi, Titus Shuuya, Leonardo Vignoli, Theo Wassenaar

Summarized by Habiba Rabiu, a student of environmental geosciences at Fort Hays State University. Habiba is interested in all aspects of environmental science and conservation & sustainability. She would like to work in educating others about those topics. In her free time, she likes to read, write, and bake.

What data were used? The welwitschia dwarf tree is a gymnosperm native to the Namib desert. It is considered a keystone species of the region, providing food, water, and shelter for the animals that live in the desert. Under the current threat of climate change, there is concern that certain parts of the welwitschia’s distribution range will no longer be suitable for their survival. 

Methods: The researchers spent ten days searching for W. mirabilis plants in the northernmost area of their traditional range. They recorded the plant locations (precise coordinates of the plant), health condition (based on leaf color to measure photosynthesis efficiency and chlorophyll content, using the classifications of good, average, poor and dead), reproductive status (whether or not the plant had cones), and plant size (diameter of the stem and leaf length) for each individual plant. Because the plants grow in clusters of four to 400, called stands, they recorded the proportion of healthy, average, poor, and dead plants in each stand, as well as the average size of the plants in each stand and proportion of reproductive to non-reproductive plants. 

Results: A total of 1330 welwitschia plants were found in 12 stands, across an area of about 215 km². The researchers found that that to be significantly smaller than what was previously considered their area of distribution. 

With regards to health conditions, most of the plants (50% total, 32–74% average in each stand) were considered ‘average’. Plants considered to be in ‘poor’ condition were 32% (range: 11–50%), those in ‘good’ condition were 10% (range: 0–30%) and seven percent of the plants were dead (range: 0–30%). Concerning reproductive status, 56% of the plants (range: 10–90% across the different stands) had cones. Size of the plants varied greatly when considered individually and in each stand. 

The overall status of the plants was considered consistent with their expected condition when taking into account the effects of climate change. The results suggested that ongoing climate change is negatively affecting the health status of welwitschia populations in the area and causing a reduction of the species’ distribution.

The black section is a squared-off area close to the northern border of Namibia with a small part of it touching the coastline. There are three red areas all relatively close to the shore, in line from north to south. Inside the black area there is a red area, and situated within that is the only blue area, which is very small compared to the black and red areas.
Larger map shows the study area (surrounded in black), the previously known species distribution (surrounded in red), and where the trees were found during the study (surrounded in blue). Insert map shows location of study, in northern Namibia.

Why is this study important? Welwitschia trees are essential to the Namib desert ecosystems and are good indicators for the overall health of the environment. Determining how they are responding to climate change could indicate what the future of the region will look like for the organisms that live there.

The big picture: While deserts are not usually thought of as teeming with life, they are important environments that house a lot of biodiversity in the form of plants and animals. The effects of global warming are and will continue to be particularly harsh on desert species. The ecosystems that exist there have to adapt to increasing temperatures that were already high to begin with, less rainfall where there was already very little, and more CO₂ in the atmosphere. These changes could greatly affect how the deserts all over the world function and whether or not the organisms that survive there will be able to continue to do so.

Citation: Bombi P, Salvi D, Shuuya T, Vignoli L, Wassenaar T (2021). “Climate change effects on desert ecosystems: A case study on the keystone species of the Namib Desert Welwitschia mirabilis.” PLOS ONE 16(11): e0259767.

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