Can this plant save the planet?

SPEKBOOM is the star of the international climate change show. It's the Greta Thunberg of the plant world and is presented as the one-stop answer to our carbon problems.

This cute indigenous succulent (Portulacaria afra), beloved by the media locally and internationally, grows easily and is drought-resistant. Everyone wants to plant it everywhere because of this “wonder plant's" special ability to remove carbon dioxide from the atmosphere. “Accept the #spekboomchallenge: plant a spekboom and do your part to combat climate change," many encourage on social media.

It's easy — just take a cutting, plant it in the ground, give it a little water, and you have a new spekboom plant. City councils, businesses and non-governmental organisations also have big planting plans. Cape Town city council wants to plant 100,000 spekboom trees, a vineyard in the Klein Karoo 1 million, and a huge spekboom labyrinth is being created in the fynbos world near Stellenbosch.

Will it really make amends for our carbon sins, or are spekboom trees the new victim of fake news and unfounded enthusiasm?

A rock star indeed, and great in salad

Spekboom, also known as pork bush, is indeed a remarkable plant and is popular for good reason. It's resilient, water-wise and versatile. It can be a shrub or a small tree, or you can prune it into a hedge, use it as ground cover or shape it into a brilliant bonsai. Spekboom is traditionally used for various ailments and can even be eaten. Feel free to add a few leaves to your salad for an extra bite — they contain a lot of vitamin C.

Spekboom occurs naturally, especially in the Eastern Cape, where it's a key species in the thicket vegetation of places such as the Addo Elephant National Park.

Elephants have a preference for spekboom, and it's good fodder for wildlife and livestock. You'll also encounter spekboom in the wild in the Klein Karoo and parts of KwaZulu-Natal, Mpumalanga and Limpopo.

So, spekboom is certainly valuable, but is it truly a marvellous carbon vacuum cleaner? Let's look at a few of the common statements going around and compare them with what scientists have found.

Myths versus facts

Statement: Spekboom is one of the most effective plant species for removing carbon dioxide from the air.

Fact: The rate at which spekboom plants photosynthesise (use light to convert carbon dioxide and water into carbohydrates and oxygen) is moderate and is more or less the same as many other plants. Therefore, the spekboom in your garden, relative to its size, will not remove more carbon dioxide from the atmosphere than the other plants you have there.

Statement: Spekboom can photosynthesise at night and can therefore survive with little water.

Facts: Spekboom is one of the few plants that can switch between two types of photosynthesis. When there is enough water, spekboom uses C3 photosynthesis, like most other plants, which means the plant loses water as it “breathes" during the day. In dry conditions, spekboom can also switch to CAM photosynthesis to “breathe" in the coolness of the night and lose less water.

Statement: One hectare of spekboom removes four to ten tons of carbon dioxide from the atmosphere per year. This is more than a hectare of tropical rainforest.

Facts: Two figures are important when determining the carbon value of a particular type of vegetation: how much carbon does the vegetation store and how much carbon could be absorbed if a damaged area were to be restored?

The thicket or valley bushveld of the Eastern Cape, where spekboom naturally occurs, does store significant amounts of carbon, especially for an area with relatively low rainfall. One study recorded 87 tons of carbon per hectare and another 209 tons. Read more about it here. However, this was in the dense, sometimes impenetrable spekboom thickets that were common in the region before overgrazing thinned them out. Is this amount of carbon comparable to that of a rainforest full of giant trees? No. Tropical rainforests easily contain 280 tons of carbon per hectare.  Read more about it here.

And temperate rainforests up to 500 tons per hectare. Read more about it below:

Carbon vacuum

How much carbon dioxide can be absorbed by planting spekboom in the overgrazed areas of the Eastern Cape? Between 3.7 and 8.5 tons of carbon dioxide per hectare per year over 25 to 30 years is considered realistic, with a maximum of up to 15.4 tons per year. Read more about it here. However, the success of plantations varies significantly from place to place. In comparison to spekboom thickets, the return of a tropical forest can absorb 3.7 to 12.5 tons of carbon dioxide per year. Read more about it here.

Statement: Given the amount of carbon dioxide that spekboom absorbs, can I significantly reduce my carbon footprint by planting spekboom?

Facts: First, keep in mind that the impressive carbon uptake of spekboom only works in its natural habitat where it grows densely for decades. Let's say you plant a hectare in the right part of the Eastern Cape: it's about the size of a decent rugby field, and you need to plant 2,000 or more finger-thick spekboom plants.

If everything goes well (no drought, curious baboons or hungry goats), you could absorb an average of 6 tons of carbon dioxide per year. Is that a little or a lot relative to your lifestyle? It's the equivalent of almost 50,000km of exhaust emissions from your new Volkswagen Polo. Your round-trip flight between Johannesburg and Cape Town emits 230kg of carbon dioxide.

Then you also need to consider the carbon footprint of your food, electricity and all the other things you consume. South Africans release 9 tons of carbon dioxide per person every year — more than double the global average. How many South Africans can afford to plant a hectare of spekboom? And how many suitable areas are there?

There is indeed significant potential to restore spekboom thickets in the Eastern Cape. The renowned ecologist, Prof Richard Cowling, has done extensive research on this subject. He emphasises that it only makes ecological and economic sense to plant spekboom on a large scale in this region: “Planting spekboom in your garden, at your office, or any other place outside its natural habitat is not environmental restoration, it's gardening," he says.

“Compared to the typical plants in your garden, spekboom's ability to sequester carbon dioxide is fairly moderate. However, in the drought-stricken valleys of the Eastern Cape facing desertification, strategic restoration with spekboom can indeed make a significant difference."

It's about more than carbon: spekboom restoration also reduces erosion, increases the carrying capacity of the land, restores water catchment areas and promotes biodiversity. It creates jobs and can give a boost to the rural economy. It is precisely for these reasons that the government's Working For Water programme, farmers and non-government organisations have already planted spekboom on about 10,000ha over the past 15 years.

Large scale restoration

Another million hectares of overgrazed land could potentially transform back into spekboom thickets, and there is growing interest locally and internationally. The United Nations' Decade on Ecosystem Restoration, launched in 2021, is one of the proponents of large-scale restoration in the Eastern Cape.

However, you cannot simply stick spekboom branches in the ground and hope for the best. Marijn Zwinkels, managing director of the non-government organisation Living Lands, involved in spekboom restoration in the Baviaanskloof, says: “A holistic approach is needed. We look at the entire landscape and collaborate with all stakeholders to develop sustainable economic models for a specific landscape. The goal is to transition from a degrading system to a regenerative one. Spekboom is a vital part of this."

Meanwhile, research on spekboom in the Eastern Cape continues. Every year, the Thicket Forum gathers all those deeply involved in thicket restoration. Two challenges being investigated are the variable survival of planted spekboom and the cost-effectiveness of large-scale restoration.

As reported by Vrye Weekblad in November 2019, we will not save the planet by planting trees.

Instead, look at your lifestyle and what you can do to emit fewer greenhouse gases, rather than hoping to offset them somehow.

Humanity is in such a dire situation and our global carbon budget is so limited that we cannot afford this approach.

A few options that can make a difference are flying less, consuming less meat, installing a solar-powered geyser or buying a smaller car.

Even more crucial are radical changes in government policies and the private sector.

Regarding spekboom outside of its natural habitat, don't get lost in a maze of good intentions or fall for opportunistic schemes. Feel free to plant a spekboom or two. After all, it's a charming plant, and we could all use more connection to the earth.

♦ VWB ♦

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