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Building back nature is more complicated than just planting trees

Image: Unsplash/ Damian Patkowski

The UN officially launched the Decade on Ecosystem Restoration programme, but planting trees anywhere and everywhere is not a silver bullet to combat climate change.

Just two months before the Intergovernmental Panel on Climate Change (IPCC) report issued a “code red for humanity” in August, the United Nations Environment Programme in collaboration with the UN’s Food and Agriculture Organisation launched the Decade on Ecosystem Restoration (UN Decade).

The UN Decade is a global call to action that runs from 2021 to 2030 and which, according to the UN, is the timeframe scientists recognise “as humanity’s last chance to prevent catastrophic climate change” and essentially gives society just shy of a decade to revive and restore what is left of Earth’s ecosystems.

During the virtual launch gala of the UN Decade, UN Secretary-General António Guterres’s opening remarks were sobering:

“We are rapidly reaching the point of no return for the planet. We face a triple environmental emergency: biodiversity loss, climate disruption, and escalating pollution. For too long, humanity has cut down the Earth’s forests, polluted its rivers and oceans and ploughed its grasslands into oblivion.

“We are ravaging the very ecosystems that underpin our societies and in doing so, we risk depriving ourselves of the food, water and resources we need to survive.”

Restoring the planet’s ecosystems is so urgent that the UN talks of a mass extinction if we fail to act within the next 10 years. 

But effective ecosystem restoration is complex developmental work that is not as simple as planting a tree here and there. In fact, the risks of tree-only campaigning to ecosystem restoration are manifold.

Emeritus professor of biological sciences at the University of Cape Town William Bond is one of the lead authors in new research busting the myth that planting trees everywhere is the silver bullet to slowing global warming and explains why we need areas like open grasslands in the savannas. 

“I am trying to champion non-forested parts of the world, ‘open ecosystems’, which are threatened by global plans to plant trees, millions of hectares of them, with Africa particularly targeted. I see this as a major threat to Africa since our sun-loving fauna and flora can be rapidly exterminated by shade of, typically, conifer and eucalypt plantations,” says Bond. 

“What many don’t realise is that grasslands store carbon in their soils and reflect more sunlight back into space than forests, playing a very important part in cooling the earth.”

Africa contains more grasses than any other continent. According to the South African National Biodiversity Institute, covering 46% of its area, the savanna is the biggest biome in southern Africa.  

Bond explains that savannas are characterised by grasslands – an open habitat peppered with a handful of trees – and that in a healthy grassland ecosystem there is a very delicate balance between trees and grasses that needs to be maintained for the diversity of animal species that it supports to survive and thrive.

Tree-planting plans to offset carbon threaten the ancient grasslands and everything it supports, he adds.

“What many don’t realise is that grasslands store carbon in their soils and reflect more sunlight back into space than forests, playing a very important part in cooling the Earth.”

Grasslands are millions of years old and Bond cautions ecosystem restoration projects to question whether the trees are restoring previously forested areas or whether they are destroying an ancient grassland and existing ecosystem.

Ecosystem restoration is an intricate process that takes time

An example of an organisation working towards realising the UN Decade’s vision in South Africa is ecosystem restoration NGO Greenpop

Greenpop began in 2010 as an urban greening initiative with the goal of planting 1,000 trees during Arbour Month. Over 11 years Greenpop has planted exactly 159,518 trees and expanded its work in four countries including South Africa, Malawi, Zambia and Tanzania, and incorporated four restoration themes including forest restoration, urban greening, food gardens and environmental awareness.

“The idea was to try and bring some greenery into spaces where there was never any real investment into greening, so we were planting mostly at schools and community centres with the purpose of trying to bring shade into these spaces and increasing pride of place,” says Greenpop’s head of programmes, Zoë Gauld-Angelucci.

Gauld-Angelucci, who has been with Greenpop for nearly eight years, completed her master’s thesis on the benefits of planting trees in an urban environment, of which, she says, there are many. 

“Trees have environmental benefits like reducing stormwater runoff and purifying the air, as well as psychological benefits like people tend to be less stressed if they have a green space surrounding them,” she explains.

“There are also economic benefits like reducing the urban heat island effect, bringing cooler temperatures into city spaces which tend to be hot because there is so much concrete and tar.”

Since 2018, Greenpop’s urban greening projects in Cape Town have changed to focus on growing fynbos instead of trees due the drought that ravaged the city and surrounding areas in 2018. 

 “A lot of climate change mitigation projects at the moment are focusing on planting forests that are not necessarily in previously forested areas and that comes with its own issues.”

Gauld-Angelucci says Greenpop’s forest restoration projects work through reforestation – regrowing/restoring a forest that has been degraded through clearing for cash crop agriculture or mining to what it once was – not afforestation – planting trees on a piece of land that was not traditionally forest.

She stresses the importance of the distinction: “A lot of climate change mitigation projects at the moment are focusing on planting forests that are not necessarily in previously forested areas and that comes with its own issues.”  

Image: Unsplash/ Steven Kamenar

Considering a site for restoration

Through its Forest for Life restoration programmes Greenpop ultimately aims to “plant 500,000 trees to restore degraded forest areas, increase biodiversity and expand ecosystem services across sub-Saharan Africa by 2025”, says Gauld-Angelucci, who explains that the essence of these projects is to view forests as a holistic part of the landscape. 

“A forest does not just sit there by itself and not interact with anything around it. There are animals and communities that rely on forests and legislation that determines use rights; there is also neighbouring vegetation that has to be taken into consideration.”

The first step in restoring any degraded landscape is to determine why the site became degraded in the first place, which means studying factors such as threats to a particular landscape to establish whether it would make a good candidate for restoration.

Gauld-Angelucci says obvious markers of degradation include when a site is devoid of vegetation but there are visible tree stumps indicating that trees have either been cut down or burnt, or where the landscape is suffering from a high degree of erosion.

Another marker of degradation is a high prevalence of alien invasive plants. “You could have a piece of land covered in trees and vegetation but it does not mean that it is healthy because it could be that those are alien species and are posing a risk to indigenous vegetation because they are a very high fire risk.” 

It is a complex, lengthy and delicate process and “we [Greenpop] would never show up at a piece of land and say, ‘hey, this looks like a good place to plant a whole bunch of trees’”.

Greenpop runs its restoration projects with local community organisations and partners where it receives applications from land owners and community organisations asking for help to restore a piece of land that has been degraded over time due to a number of reasons.

The next steps include determining what vegetation the site should be restored to and appropriate methods.

“This is an incredibly complex step and you have to approach it from multiple angles,” says Gauld-Angelucci, explaining that the main way Greenpop determines the history of any degraded site is through Biodiversity Geographic Information System maps provided by the National Biodiversity Institute. These show the indigenous ecosystems for every part of South Africa.  

“You can zoom in and determine whether an area was once Afromontane forest or Cape Flats Sand Fynbos, for example. This is usually a really good method to determine what type of vegetation the land was covered with before it was degraded.”

Sometimes, however, the land can be a “mosaic area”. 

“This means the landscape can support forest as well as fynbos and what probably happened in the past was the forest and the fynbos lived next to each other in patches and then the fynbos would catch on fire and some of the forest would burn down and then there wouldn’t be a fire for a while and some of the forest would take over the fynbos land and there is this kind of dance that goes on over the centuries,” she explains.

Determining where the borders of forest and fynbos start and end in a mosaic area makes the restoration process more challenging, but by using as many resources as possible, from historical Geographic Information System maps, to talking to residents who have been in the area for a long time, Greenpop can get a good idea of what the area looked like before and how best to restore it.

“One of the things we also always look at as well are existing forests, the topography and patterns of growth in an area. In most of the places that we work there are existing patches of indigenous forest that have been conserved over time, so we often work on the edges of those forests,” Gauld-Angelucci says.

“We also have to look towards the future and say, well, we are living in an age of climate change so we also need to be thinking about the fact that climates are going to be getting warmer and what vegetation is going to be sustainable in areas marked for restoration when it is one degree or 1.5 degrees hotter.” 

Platbos Forest Reserve restoration project

Greenpop has been working on a restoration project with the Platbos Forest Reserve in Uilenkraal Valley in the Overberg for 10 years. Platbos is an ancient indigenous forest – the trees are about 1,000 years old – as well as the southernmost forest in Africa.

Owners Francois and Melissa Krige began restoring the land 15 years ago when alien vegetation surrounding the forest began to pose a fire risk.

The Kriges did this by finding seedlings in the indigenous forest, growing them in their nursery and when they were old enough, planting the trees in the area cleared of alien vegetation.

Gauld-Angelucci says the Kriges recently finished clearing the alien trees from the indigenous forest after 15 years.

Bodhi Khaya Nature Retreat. Image: Greenpop

Greenpop came along in 2011 and started running festivals in Platbos every year, bringing in hundreds of people to help with the reforestation.

“For the most part Greenpop has been helping by filling in gaps in Platbos and have planted exactly 85,645 trees in that forest so far, including white milkwoods, white stinkwood, wild olives… all the indigenous trees that exist in the forest already, and we plant them in an interesting way: we dig pits and those pits get filled with mulch and the trees get planted around the pits in groups because that is the way the trees grow within the forest on their own. 

“Generally, a tree will die, fall over and rot and then lots of little trees will start growing around it because the dying tree provides nutrients and an all-round conducive space to grow for the new trees, and we try to recreate that environment.”

Grootbos Private Nature Reserve restoration project 

Restoration is ongoing, so much so that Gauld-Angelucci hopes that Greenpop will be able to say that full restoration will be complete in 100 years.

“There is a lot of land left in that area to restore. There are a few other landowners and organisations in the broader Uilenkraal Valley landscape that have reforestation projects in the pipeline and we fully acknowledge that most of the valley is fynbos so we are trying to bring everyone together to come up with a consolidated strategy for the valley (what areas should be restored to forest and which areas should be restored to fynbos) moving forward so that we can be sure that we are not reforesting where we shouldn’t be.”

Paleoecology researchers from UCT are working on this, and heading the research is professor in plant conservation in the Department of Biological Sciences, Lindsey Gillson. 

Gillson says they are using markers such as fossilised pollen and charcoal in soil samples to determine the ecological history of various sites in the Grootbos Private Nature Reserve, which is also in the Western Cape’s Overberg region.

“While [global tree-planting drives] can have benefits if carefully planned and managed, there is also a risk that afforestation on ancient open, grassy and mosaic landscapes can be bad for biodiversity and ecosystem services.”

Grootbos is a mosaic landscape comprising predominantly fynbos and only patches of forest, but Gillson says “forest restoration is nevertheless an important element in the management of Grootbos and so understanding the history of forest in terms of forest extent and composition is therefore important in guiding restoration that is ecologically appropriate”.

In paleoecology (the study of the interactions between plants, animals and past environments), different indicators are used to reflect the different parameters of environmental change. 

“They are ‘proxies’ in that they are not direct reflections of past change but are linked to them,” says Gillson. “For example, we can reconstruct changes in fossil pollen abundance and use this to infer changes in vegetation; in this case, the pollen is a proxy for vegetation abundance.”

Paleoproxies can come from lake or wetland sediment, soil, and tree rings and include charcoal to indicate fire history, diatoms to indicate climate and dung fungal spores to indicate herbivory.

“In our lab, we collect sediment cores from wetlands and extract fossil pollen and other proxies from multiple points along the core to reconstruct change over time. We [use] AMS radiocarbon dating so that we can describe changes in vegetation relative to key environmental and social-ecological changes.”

Image; Unsplash/ Tanya Paquet

Why is this important?

While satellite imagery is commonly used to track rates of deforestation over time, Gillson says that sometimes the data do not go back far enough to define vegetation composition before intensive human impact, which means the risks of restoring a site with the wrong vegetation and doing more damage than good to an ecosystem are much higher in often well-intended, climate change mitigation initiatives like global tree-planting drives. 

“While this approach [global tree-planting drives] can have benefits if carefully planned and managed, there is also a risk that afforestation on ancient open, grassy and mosaic landscapes can be bad for biodiversity and ecosystem services.”

The paleoecology work Gillson and her team do can help to ensure this does not happen by comparing current with past forest extent. Although exact locations cannot be reconstructed from fossil pollen, they can compare changes in the relative abundance of forest and fynbos over time. 

“What will be particularly important at Grootbos will be to see how extensive forests were before European settlement, when we know that timber harvesting might have led to depletion of forests,” she notes. “We can also look at forest composition and help identify trees that might have been lost from current forests due to preferential harvesting of high-value timber.”

Gauld-Angelucci adds: “The hope is that this research will add an additional layer of explanation onto the area and we can be that much more certain that what we are doing is the appropriate intervention.” 

The dangers of restoring a site with incorrect vegetation

Using the example of Grootbos, Gillson explains that while restoration of former forest patches would be ecologically valuable, expansion into former fynbos areas could threaten unique plants and is likely to be unsustainable because of the fire and water sensitivities.

“The drive to plant trees can damage the biodiversity of other ecosystems, for example, fynbos shrublands, grasslands, and mosaic landscapes that would naturally have been a mix of forest and non-forest patches. This is especially the case when non-native tree species are used. As well as taking up space, they can affect ecological processes like soil formation, hydrology and fire.”

 “Planting forests in the wrong place with the wrong species can be devastating for biodiversity, ecosystem services and communities.”

By identifying the past forest extent and composition, as well as which open landscapes were ancient or man-made, can help guide conservation and restoration that includes a wider range of ecosystem types and is better for biodiversity and ecosystem services.

Gillson also points out another danger of afforestation or restoring a site with the incorrect vegetation is the possibility of negative effects on carbon storage and other ecosystem services. 

“If only above-ground carbon is calculated, planting trees can seem like a good option, whereas in fact more carbon is often stored in soils in most ecosystems (not tropical forests). The single-minded focus on carbon storage can also neglect other important ecosystem services such as water provision, grazing, and non-timber forest products that are often important to communities and livelihoods.” 

Carbon offsetting and planting trees to slow global warming

Deforestation is a huge global concern and most people are aware of the crisis and common deforestation examples such as the Amazon basin. They also understand there is an urgency to act on the climate crisis support for forest restoration as it appears to benefit both biodiversity and climate. 

This, Gillson says, is the crux of the tree-planting frenzy, and the very important distinction between restoring forests (which have been destroyed by people) and planting new forests is getting lost. 

“Planting forests in the wrong place with the wrong species can be devastating for biodiversity, ecosystem services and communities. Paleoecology offers techniques that can explore past forest extent and composition, but it is currently underutilised in restoration ecology.”

Gauld-Angelucci points out that the main thing to consider in restoration projects is that the indigenous vegetation must never be replaced or “out-competed” and that whatever is being added to the landscape needs to be supportive of the existing ecosystem rather than in competition with it – to avoid the danger of it overtaking and eventually killing the ecosystem – as is the fear with the AFR100 challenge which aims to fill 100 million hectares in Africa with trees by 2030.

“The risk of potentially damaging the naturally occurring ecosystems is something that is of primary concern to people working within the fynbos and grassland restoration and conservation space because trees get a lot of attention and I think there have been so many ‘challenges’ and ‘pledges’ with these tree-planting targets that I think people who are working in other types of conservation get nervous that trees are going to be planted all over the place which do not value the indigenous ecosystems that already exist.” 

Many companies, especially in the fast-fashion industry, have recently pledged to work towards “carbon neutrality” through large-scale carbon offsetting projects such as tree-planting initiatives or building wind farms. They include the Kering Group, the parent company of haute couture brands such as Gucci, Saint Laurent and Bottega. 

Gillson says carbon offsetting allows entities that are emitting carbon to buy credits that are used to increase carbon storage elsewhere. “For example, when taking a journey by plane, one can often now pay a carbon offset that allows the airline to contribute to a carbon storage project elsewhere.”

While Gauld-Angelucci acknowledges that people can make choices that are more sustainable or less sustainable, she points out that we are living within systems that promote unsustainable behaviour and that carbon offsetting initiatives may be fine as a short-term measure, but not a long-term solution. 

“There are so many things that go into a forest restoration project because a forest does not sit on a little island by itself.”

“We actually have to take a look at the way our current industries are functioning and see where the changes can be made within those systems. It is not enough to ‘offset the carbon by planting a tree’, pat ourselves on the back and continue exploiting people and the Earth for profit – whole industries need to be tackled. It really is not as simple as, ‘let’s just plant trees everywhere and we’re going to solve climate change’.”

Gillson agrees with Gauld-Angelucci that we need to tackle global heating with everything that we have.

“Carbon offsetting can be valuable if the carbon projects take account of all ecosystem services and the communities who depend on them, but radical changes are needed in consumption and production patterns if we are to meet global climate change targets,” she says. “Carbon offsetting projects must consider biodiversity and ecosystem services, not just carbon storage.”

Gauld-Angelucci adds: “What I find challenging is that people want a simple solution to what is actually quite a complex process and when they think of a tree being planted, all they think about is the tree and somebody putting it in the ground or a drone dropping a seed.”

It is not that simple.

There are many moving parts involved in the restoration process, including communities, legislation that needs to be addressed and regular monitoring and evaluation to make sure the restoration process is working and sustainable.

Gauld-Angelucci says “quick-fix” initiatives like tree-planting arise from the oversimplification of the narrative around environmental issues and what can be done about them. 

“The thinking that you can plant a tree anywhere comes from not understanding or misunderstanding the basics of ecology and that specific species belong within specific ecosystems and that planting them outside of their relevant ecosystems can have bad effects; most people are not aware of this, especially because within our own back gardens there is a culture of picking out whatever you like and just planting it there, in your garden.

“There are so many things that go into a forest restoration project because a forest does not sit on a little island by itself; it is part of a broader landscape and it is basically development work and that is complicated and messy and expensive – but it is the most important, impactful work to do.” DM/ML

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  • A pretty comprehensive article about the issues that must be resolved in any attempt to plant trees in order to sequester Carbon, so it is fairly surprising that no mention was made of the technique known as FMNR. Probably my least favorite acronym it stands for Farmer Managed Natural Regeneration and is a simple technique whereby farmers (or other land-owners) manage the coppice growth on stumps of trees felled for any reason. Many African species of tree will send out coppice shoots from a living stump; if all these shoots are trimmed off leaving just the biggest most dominant one, that single shoot will grow much faster and soon grow away from the threat of livestock or fires. The process is MUCH quicker than planting trees (as the stumps already have a substantial root system) and also ensures that the same species mix is restored to a previous area of woodland or forest. These species must, almost by definition, be appropriate to the local conditions. Whatever technique is used, even whether we use grassland or woodland, we should remember the goal is to restore the most appropriate Ecosystem while drawing down as much CO2 as possible into the biomass and the Soil. Bruce Danckwerts CHOMA Zambia