Trees alone will not save us

There’s increased understanding that not only do we need to cut carbon dioxide emissions, we also need to pull it from the atmosphere. Recently trees have come into fashion as the answer. This need has led to the Trillion Tree Campaign and a company in the UK planting giant redwoods to offset a lifetime’s carbon on the basis that “planting native trees to combat climate change is a little like bringing a water pistol to a gun fight.” Ecologists working outside forests could feel a little neglected. Research recently published in the Journal of Applied Ecology by Fernando A. O. Silveira and colleagues showed that they’d be right. And it’s not just the public that is fixating on trees. The study shows that scientists and policymakers are focussing disproportionately on trees too. This problem, which they label Biome Awareness Disparity or BAD, could have consequences for conservation in the future.

What is a Biome?

Biome seems to be one of the awkward words where everyone knows what it means until you try to pin it down. Broadly biomes are where ecosystems meet geography, so examples are Tropical Rainforests, Deserts or Grasslands. If this seems a little vague, it’s because they were initially defined by Eurocentric scientists based on climate alone, said lead author Fernando Silveira in an email to Botany One. Opinions are changing as ideas clash with reality, and more useful definitions are being developed. But the European colonial legacy is an ongoing problem. The notion that reforestation is the best form of restoration is a similar problem, says Silveira.

“One of the reasons why this misconception is so widespread is that most science is done by north-hemisphere scientists who live in forested areas. Thus, people tend to think this is the standard everywhere else. But if you go to the tropics, this is far from the reality. Many areas which are savannas or grasslands have been depicted as forests. As a consequence, people think they should plant trees over there to ‘restore’ the forests.”

The authors can list many tree planting initiatives, from 1t.org to the Bonn Challenge to the New York Declaration on Forests. But is this a matter of the media not keeping up with what’s going on, or is it a reflection of a genuine problem?

Silveira and colleagues took a two-pronged approach.

Is the focus on trees a policy or media problem?

For policy and the media, the team analysed 50,000 tweets from all Partner Institutions of the UN Decade of Ecosystem Restoration and 45,000 tweets from the main science and environmental news media worldwide. The results were very clearly biased to one type of biome.

“Disparities in attention and interest were demonstrated in tweets by the Partner Institutions of the UN Decade of Ecosystem Restoration, which largely focused on forests. Open biomes received far less attention in relation to their area… (9.6 times more tweets for forests than for open biomes…). However, we found no differences in the number of likes… and retweets… between forest and open biomes,” wrote the authors.

That difference of over nine times more tweets for forests would not be significant if there were nine times more forest area in the tropics than open biomes. In fact, there are slightly more open biomes.

One possible criticism is that the Twitter collection was loaded in favour of tree-based initiatives and, naturally, they’ll be tweeting about trees. The selection of Twitter handles examined includes @AmericanForests, @Cities4Forests, and @Forests_Ontario. It would be odd if they were indifferent to trees. So have the team simply found that tree-oriented Twitter accounts tweet about trees?

The counterargument is that these organisations are doing an excellent job. Still, suppose you’re examining all Partner Institutions of the UN Decade of Ecosystem Restoration. In that case, the forest-focussed tweets from the tree initiatives will be counter-balanced by grassland-focused tweets from projects like @Savannahs4Savannah, @GreatGrasslands and @GreenSerengeti – but these projects don’t exist. The public face of Ecosystem Restoration is overwhelmingly tree-based because this is what is getting supported.

One of the interesting comments in the paper is that the likes and retweets seemed to be similar for projects on forested and open biomes. This equality indicates that the general public support, or are at least have an interest, in all ecosystem restoration and are ahead of the policymakers.

Is the focus on trees a science problem?

In an ideal world, policy would follow the science. Is the science being ignored? For the second approach, Silveira and colleagues conducted a systematic literature review in Web of Science for restoration ecology in the tropics to determine which biomes were being studied as suitable for restoration. They found over three hundred and fifty primary reports of field-based studies. The team worked out where the studies were and if the researchers used tree-planting.

“We found strong disparities in action across tropical biomes…, with restoration studies concentrated in rain forests (~70%), dry forests (15%) and mangroves (0.9%),” write Silveira and colleagues. “This disparity cannot be explained by area covered by forests (χ2 = 284.4, p < 0.001), since forest biomes cover around 43% of tropical and subtropical lands… Restoration in tropical and subtropical grasslands, savannas and shrublands were strongly underrepresented in restoration studies (8.9% of the cases vs. 39.0% tropical area. The strongest disparities in restoration actions occurred for deserts and xeric shrublands, which were the least represented biomes…”

If around 86% of restoration studies are in forested biomes and just 8.9% in grasslands, then it would seem that policymakers and the media are doing a fair job of following the scienceand that scientists have a problem seeing biomes.

What are the consequences of BAD?

“Our results suggest that BAD not only exists, but it is also pervasive in tropical ecosystem restoration,” wrote Silveira and colleagues in their article. “Indeed, we found strong disparities in attention and interest relative to biome extent and diversity, with tweets focused disproportionately on forest restoration. Similarly, we found that restoration studies are concentrated in forest biomes. Because these results indicate failures to recognize the importance and understand the ecology of overlooked biomes, we suggest that until BAD is addressed and fixed, ill-conceived conservation and restoration policies will threaten to exacerbate degradation and neglect of open biomes across the tropics and subtropics…”

It can be difficult to find research showing damage done by reforestation because so many scientific articles are studies of using reforestation to mitigate damage. Shixiong Cao and colleagues have been studying some of the problems of reforestation in China over the past decade.

Silveira also points to the Cape Town Day Zero drought as another example of reforestation gone wrong. On the Western Cape is fynbos, areas of shrubland with cool, wet winters and hot, dry summers. It’s not a region that has many tree species. However, there is a need for timber, and entrepreneurs have settled pine plantations. The trees escape, and they’re thirsty. The result is that invasive trees displace the native flora and take water that would be available for humans.

It’s not just water that’s a problem with trees. There’s also fire. A recent study found that the pines are helping dry the landscape and adding more biomass to burn. Commenting on the research in a press release, Prof. Brian van Wilgen, a fire ecologist, said: “By increasing the amount of fuel available to burn, the fires become more intense and more difficult to control.”

Other research has concluded that using afforestation for combating climate change is effectively “Trading Water for Carbon with Biological Carbon Sequestration“, which will have consequences for ecosystems built on higher water flows.

What is there to lose?

A part of the problem may be the words we use. Silveira and colleagues describe projects in dryland forests, wetland forests and mangroves. In contrast, there is ‘grassland’ or ‘savannah’. In his email to Botany One, Silveira is concerned about the language we use.

“The world is rich in the diversity of grasslands, from disturbance-driven grasslands to edaphic grasslands, from tropical to subtropical grasslands. We need a vocabulary to describe their diversity. We have a good vocabulary for forest dynamics such as deforestation and reforestation. But what do you say when a grassland or savanna is lost or restored? There is no useful and accurate word to describe dynamics in grasslands and savannas. Savanna does not do justice to all diversity. Some people have suggested non-forest ecosystems, but this is problematic since it’s hard to define something by which it is not.”

“A very popular and widespread myth is that forests are the supreme homes of biodiversity and the major providers of ecosystem services. However, evidence supports the idea that open biomes have slightly lower, sometimes similar and rarely more biodiversity than their forest counterparts.”

Silveria also adds that open ecosystems can sequester carbon too.

“Open ecosystems are fire-prone, so most of their biomass is stored underground. You can’t see the carbon sinks using satellites, and most people still ignore that key role of open ecosystems in regulating and mitigating climate change.”

What can be done?

In their article Silveira and colleagues propose five steps to improve biome awareness. A challenge is for scientists to accept the limitations of current approaches without discounting all the value of current work.

“Scientists need to remove their biases towards open ecosystems. This doesn’t mean devaluing forests. They should embrace the diversity of natural ecosystems in our world and value open ecosystems at the same level of forests,” says Silveira.

“A major problem we show in the paper is the use of forest- and tree-centric approaches to the restoration of open ecosystems. Why would you plant trees in a treeless ecosystem? There is an urgent need to quickly develop restoration strategies for open ecosystems that shift away from the forest bias. Scientists need to develop techniques tailored for open ecosystems and to achieve that, scientists need funding.

“NGOs, governments and the media also can play a role. All together, they should understand that forest-focussed solutions won’t protect biodiversity in open ecosystems. Major changes in vocabulary, policy and practice are needed.

“We need a global understanding and recognition that open ecosystems are home to unique biodiversity, provide key ecosystem services and protect the livelihoods of hundreds of millions people.”

Silveira hopes that re-thinking ecological restoration will improve conservation and eliminate some work that seems almost absurd.

“People have planted pines in the fynbos and the pine plantations have drained the water. Now they’re cutting the trees as a restoration strategy. Who would have thought that cutting, not planting trees, could be a restoration strategy?”

RESEARCH ARTICLE

Silveira, F.A.O., Ordóñez‐Parra, C.A., Moura, L.C., Schmidt, I.B., Andersen, A.N., Bond, W., Buisson, E., Durigan, G., Fidelis, A., Oliveira, R.S., Parr, C., Rowland, L., Veldman, J.W., Pennington, R.T., 2021. Biome Awareness Disparity is BAD for tropical ecosystem conservation and restoration. J Appl Ecol. https://doi.org/10.1111/1365-2664.14060