An international group of ecologists contests an article published in Science, which among other cardinal errors proposed ‘reforestation’ of the Cerrado, Brazil’s savanna biome
Fundação de Amparo à Pesquisa do Estado de São Paulo
An article recently published in Science, entitled “The global tree restoration potential”, presents what it calls “the most effective solution at our disposal to mitigate climate change”. The lead author is Jean-François Bastin, an ecologist affiliated with the Swiss Federal Institute of Technology (ETH Zurich).
The article attracted enormous media attention. It reports the results of a study in which Bastin and collaborators used remote sensing and modeling techniques to estimate that forest restoration in areas totaling 900 million hectares worldwide could store 205 gigatonnes of carbon.
The study was contested by a large international group of ecologists led by Joseph Veldman, a professor in Texas A&M University’s Department of Ecosystem Science and Management (USA). At the invitation of the editors of Science, the group formulated a reply, now featuring on the October 18th edition of Science under the title “Comment on ‘The global tree restoration potential’..
Its authors include William Bond, Emeritus Professor in the University of Cape Town’s Department of Biological Sciences (South Africa) and considered the world’s foremost expert on savanna ecology. Several Brazilian researchers also co-authored the reply, such as Giselda Durigan, affiliated with the São Paulo State Forestry Institute’s Ecology and Hydrology Laboratory.
“The plan proposed by Bastin et al. is based on flawed calculations and is actually a threat to the planet’s savannas, meadows and water resources,” Durigan said.
Bastin and collaborators made “extremely basic mistakes,” she added, such as including among reforestable areas Yellowstone National Park in the US, Los Llanos in Venezuela (considered one of the world’s most important ecosystems), and the Cerrado in Brazil.
The Cerrado is the world’s most biodiverse tropical savanna and gives rise to some of Brazil’s major rivers, such as the Xingu, Tocantins, Araguaia, São Francisco, Parnaíba, Gurupi, Jequitinhonha, Paraná and Paraguay, among others.
“Unfortunately the key premises used in the study and the calculations performed by the authors are incorrect, resulting in a fivefold overestimation of the potential for forest planting to capture carbon and mitigate climate change,” Durigan said. “Furthermore, Bastin et al. included in the map of lands with potential for reforestation many areas in which trees would reduce surface albedo and intensify global warming. Worse still, they propose forest planting in almost all areas of grassland and tropical and subtropical savanna in the world.”
Albedo is the amount of solar energy reflected by Earth’s surface. The darker the surface, the less sunlight it reflects and the more it absorbs. The solar energy absorbed is converted into heat. Forest absorbs far more solar energy than open grassland. When a meadow is transformed into forest, the area absorbs more energy and can contribute to global warming.
Moreover, science has demonstrated that an increase in tree biomass impairs water production in river basins because rain is largely retained by the canopy and the trees consume large amounts of water to survive.
In sum, reforestation is an excellent idea but it is necessary to know where and how to implement it. The topic is complex and involves multiple parameters and variables, all of which the authors of an article in Science should know.
“Bastin and collaborators focused too narrowly on the carbon balance, and to make matters worse they miscalculated by underestimating the carbon trapped in the ground under open vegetation, while overestimating the capacity of trees to store carbon,” Durigan said.
“The article has undermined a good idea by being overambitious and grandiose. Many areas that once had forests and are now degraded could indeed be reforested with very positive results, but this would require far more judicious selection of areas, taking into account all the knowledge acquired to date, which goes well beyond the data obtained by remote sensing and modeling.”
Grasslands and savannas are natural formations but are treated as degraded areas in the article.
“They overlooked the fact that climate isn’t the only natural variable affecting biomass in ecosystems. They also ignored recent research showing that large-scale tree planting in grasslands and savannas can have highly negative consequences for biodiversity and ecosystem services in these more open landscapes, which have been maintained for millions of years by natural fire and herbivory regimes,” she said.
In Durigan’s opinion, the article by Bastin et al. drew exceptional attention because it pleased large corporations and countries that benefit from fossil fuel burning to drive their economies. “If the world believes the arguments presented in the article, the pressure for corporations to reduce fossil fuel emissions will be considerably weakened,” she said.
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WOW! We need more C02 to green the earth more !!!!
Not much mention of role C02 plays in greening the earth. I think YouTube and Google has removed a lot of Dr Patrick Moore videos … – in this video fast forward to about 9 mins where he starts talking about greening the earth and C02:
We actually need more C02 to green the earth more… No mention of this in the article or in the comments I read.
Fast forward to about 9 minutes to see any mention of C02 and greening of the earth:
https://www.youtube.com/watch?v=JYQ6eZDXXRE
Dr Patrick Moore… read… and do some research.
– JPP
I think there is a basic misconception in this article stating that forests prevent river outflows. For gawds sake, the whole Amazon basin has enormous river outflows and they stem from climax tropical jungle. So trying to say trees stop river outflow is bunkum at best and wilful lying at worst. Trees may absorb more water but they breathe a lot out too through transpiration.
What forests do very well is reduce peak river flows after heavy rainfall, since in general forest floors can hold a lot of water before runoff occurs.
It is quite clear politics is driving both sides of this argument.
The best to start reafforesting is where forests were previously cut down. You know, all those bits of the Amazon, all those SE asian islands, the Scottish Highlands where the Caledonian forest existed, etc etc. Places you knows forests grow well, because they grew well before humans cut them down.
The other fallacy is relating to albedo, specifically that forests warm the Earth by altering albedo and lowering as compared to bare ground.
The truth of course is far more complex, but climate sciencism does not do “complex”.
“Plant a tree” is the new wonder remedy for climate change.
The problem is that all organisms eventually die, and once a tree die, it will rot, and all the carbon it has captured during its entire lifetime are released back to the atmosphere.
/Jan
Not if you turn it into charcoal first. Biochar is the real practical and cost effective solution. Takes over a thousand years on average to release the carbon back into the atmosphere. Regenerates the soil by enhancing microbial life.
A little more than 200 million years ago, a forestation event almost led to the extinction of all life. Nature did not know a method to decompose lignin which is a major component of wood. This means that when trees died, they toppled over but could not rot in order to release their carbon back into the atmosphere. New trees sucked ever more carbon out of the air until carbon concentration was very low. So low that Earth flirted with the idea of mass suicide due to carbon starvation. Luckily, nature developed organisms that could digest lignin and CO2 concentration sprung up again. There was another brush with carbon suicide during the ice ages. Earth is dangerously low on carbon. A concentration wy above 1000ppm would be way more healthy. Industrial civilization and its carbon emissions gave Earth another lease of life.
One of the authors of the rebuttal article in Science, Will Bond, is a well established expert on the equilibrium between forest and grassland.
https://onlinelibrary.wiley.com/doi/abs/10.1046/j.1365-2486.2003.00577.x
He showed how changes in CO2 concentration lead to grasslands where CO2 is low, since trees grow slower and take too long to get to a size to resist fires. Conversely, when CO2 rises, trees grow faster and can repopulate grassland areas.
Therefore since we are increasing CO2, we are also increasing forests worldwide at the expense of some grasslands. This is happening naturally without any need of human intervention (other than carrying on burning carbon 🙂
The Cerrado savanna has been managed with/by anthropogenic fire for millennia.
From: Kayapó Savanna Management: Fire, Soils, and Forest Islands in a Threatened Biome by Susanna B. Hecht, Chapter 7 in Amazonian Dark Earths: Wim Sombroek’s Vision, William I. Woods (Editor), Wenceslau G. Teixeira (Editor), Johannes Lehmann (Editor), Christoph Steiner (Editor), Antoinette M.G.A. WinklerPrins (Editor), Lilian Rebellato (Editor). 2009. Springer.
The Kayapó burn the Cerrado systems in many complex ways, although the intentionality of the burning in some cases may be open to speculation. The Kayapó burn throughout the dry season, the burning is usually done early in the day. The spatial mosaic of the burning is very uneven, creating a pattern of burn history of different extent, intensity and age and types of ash depending on the burn temperature. As has been noted elsewhere, burning is a constant feature of Kayapó resource management and throughout the dry season one is in a kind of smoldering landscape (Hecht 2003, 2005).
Yellowstone National Park is cited as a bad place to reforest. My wife and I spent four days there in July, and one of the things we saw were hundreds, perhaps thousands of acres of forest that had been burned out by recent wild fires. What would be wrong with reforesting that?
It would appear that everything these days is seen through the polarising filter of climate change; What about other issues? In many places so-called “invasive specie” trees are being removed on the basis that they use up too much water. Would it not then make sense to plant these or similar water intensive trees in the catchment areas of rivers prone to flooding so as to mitigate the flooding potential? Nature does not respect the boundaries we place on it for study purposes….
It would be extremely ironic if massive forests were planted out to sequester CO2 and in turn later it’s discovered that water vapour was the driver not CO2. All that additional transpiration adding water vapour to the atmosphere.
On another note for the scientists, is it possible that due to increased urbanisation, buildings, infrastructure , roads, rail etc etc (because of the rising human population) it has added immense additional surface area (like compare the land area vs the surface area of a high-rise building on that land) to the planet’s surface and that is what has contributed to warming?
The type of surface it is holds heat (concrete, bricks, bitumin, steel etc). Now similar to the alloy cooling fins on an amplifier’s heat sink the air passes by/between and warms. Could it be enough to alter the temperature?
As a person who spends a fair amount of time outdoors, I also notice that the ambient night time temperature around trees is warmer than in an open field. The trees retain heat over night. A lot cozier in a forest than an open field at night. Now if temperature drops 6.5C per 1km higher we go, then holding that heat small percentage of heat back with trees and additional urban sprawl could have been enough to do the 1C change we’re measuring at surface?
“prevent the night’s heat flow from the surface to the sky, thereby altering local climates and comfort levels”
Source:- https://link.springer.com/article/10.1007/s11252-015-0447-7
“During the night, diameter at breast height and tree decay class were important, such that larger, live trees cooled down less.”
Source: https://bioone.org/journals/journal-of-wildlife-management/volume-74/issue-8/2009-560/Thermal-Properties-of-Tree-Cavities-During-Winter-in-a-Northern/10.2193/2009-560.short