Previously, I introduced the concept of Solar Radiation Management (SRM) which gains increasing prominence as an option to combat global warming. This post will look at SRM’s counterpart – Carbon dioxide removal (CDR). I will further examine a CDR technique which attracted my attention in the geoengineering seminar some weeks ago – it’s trees!
Whereas SRM seeks to slow down further climate warming through a reduction of radiation absorbed, CDR addresses the greenhouse gas effect through the large-scale removal of carbon dioxide from the atmosphere thus generating so-called negative emissions. The math is simple: Today, there is about 408 ppm of CO2 in the atmosphere, about 4 ppm more compared to this time last year (find all current and recorded CO2 levels here). Even though various scientists agree that the safest way to halt emissions growth is reducing emissions released in the first place, many argue that artificial alternation of carbon levels will be both possible and most importantly necessary in the future (The Royal Society, 2009). There are numerous ways to remove carbon from the atmosphere. Hitherto the most popular one might be Carbon Capture and Storage (CCS). This, in brief, means taking carbon from the atmosphere and pressing it in the subsurface, by using biomass (which naturally stores carbon dioxide) or by filtering out carbon dioxide. Both of these techniques are already in place in some small-scale sites (Venton, 2016). In Iceland, significant CCP progress is made just now:
Another approach in CDR is trees: Forests absorb around 30% of all CO2 emissions from burning of fossil fuels and deforestation (Candell and Raupach, 2008). Afforestation appears as a straight-forward answer to atmospheric carbon levels. One simulates natural processes of carbon storage (simply) through planting trees. Let’s unpack afforestation further.
Talking of trees, one distinguishes between afforestation and reforestation. Afforestation is referred to as converting land to forests that have not been forested before whereas the latter is the process of re-establishing formerly forested areas. Providing afforestation and deforestation are taken seriously by the global community and executed effectively it is estimated that atmospheric levels of CO2 can potentially be reduced by up to 70 ppm in 2100 (Candell and Raupbach, 2008). The reduction can be achieved by increasing the net area of forests and through increasing the density of forests providing sufficient protection and conservation of existing and future forests are in place. China, for instance, has successfully transformed or restored 24 Mha of land to forests thus setting off 21% of its fossil fuel emissions in 2000 (unfortunately, China's emissions level have increased by up to 150% since then, Grubb et al. 2015). Additionally, in tropical regions forests cause clouds formation which raises the albedo in theses latitudes increasing the large-scale mitigation effectiveness of forests.
Whereas SRM seeks to slow down further climate warming through a reduction of radiation absorbed, CDR addresses the greenhouse gas effect through the large-scale removal of carbon dioxide from the atmosphere thus generating so-called negative emissions. The math is simple: Today, there is about 408 ppm of CO2 in the atmosphere, about 4 ppm more compared to this time last year (find all current and recorded CO2 levels here). Even though various scientists agree that the safest way to halt emissions growth is reducing emissions released in the first place, many argue that artificial alternation of carbon levels will be both possible and most importantly necessary in the future (The Royal Society, 2009). There are numerous ways to remove carbon from the atmosphere. Hitherto the most popular one might be Carbon Capture and Storage (CCS). This, in brief, means taking carbon from the atmosphere and pressing it in the subsurface, by using biomass (which naturally stores carbon dioxide) or by filtering out carbon dioxide. Both of these techniques are already in place in some small-scale sites (Venton, 2016). In Iceland, significant CCP progress is made just now:
A "Climate Change Breakthrough" is what The Guardian calls the development at the Hellisheidi power plant in Iceland. And, fairly, it is rather magnificent: The engineers of the CarbonFix project dissolve carbon dioxide in water and inject it into the volcanic rock under the ground. There - and that is the interesting part - it reacts with basalt and forms carbonate minerals (essentially limestone) within two years. Essentially this is a natural process, except it usually takes several hundreds of years for the carbon acid to solidify. Scientifically and politically, the unexpected discovery might give the current CCS discourse another push as the 'limestone-making' is considered one of the safest ways to deal with carbon underground. Yet, it takes a large amount of water to dissolve required amounts of carbon which poses another threshold. For now, however, Iceland indeed - I apologize for this one - rocks.
Another approach in CDR is trees: Forests absorb around 30% of all CO2 emissions from burning of fossil fuels and deforestation (Candell and Raupach, 2008). Afforestation appears as a straight-forward answer to atmospheric carbon levels. One simulates natural processes of carbon storage (simply) through planting trees. Let’s unpack afforestation further.
Talking of trees, one distinguishes between afforestation and reforestation. Afforestation is referred to as converting land to forests that have not been forested before whereas the latter is the process of re-establishing formerly forested areas. Providing afforestation and deforestation are taken seriously by the global community and executed effectively it is estimated that atmospheric levels of CO2 can potentially be reduced by up to 70 ppm in 2100 (Candell and Raupbach, 2008). The reduction can be achieved by increasing the net area of forests and through increasing the density of forests providing sufficient protection and conservation of existing and future forests are in place. China, for instance, has successfully transformed or restored 24 Mha of land to forests thus setting off 21% of its fossil fuel emissions in 2000 (unfortunately, China's emissions level have increased by up to 150% since then, Grubb et al. 2015). Additionally, in tropical regions forests cause clouds formation which raises the albedo in theses latitudes increasing the large-scale mitigation effectiveness of forests.
Large-scale afforestation projects such as the Green Great Wall project in Africa have also proven to be a boost for the local economy resulting in significant socio-economic benefits. Through the beforesaid advantages and the relatively low price of afforestation (compared to large-scale bio-chemical climate alterations) as well as immediate accessibility, institutions such as the UNFCCC promote afforestation in particular (Horton et al., 2016).
In general, reforestation appears to be the much less controversial approach compared to afforestation. Many agree on the need to conserve existing forests through the relevance of their ecosystem services and their contribution to the global climate.(Chakravarty et al., 2012). Afforestation is discussed more critically. Depending on what areas are converted the benefits can potentially be offset by negative side-effects. In Savannahs, for instance, endemic species could lose its habitat and local biodiversity could suffer. In boreal regions, newly planted trees might lower the albedo as leaves absorb more radiation than snow. Moreover, there can be economic shortcomings in agriculture through land loss. Even if trees are planted at suitable locations such as unused or unwanted land, they (obviously) grow very slowly thus marginally affecting carbon levels in the short-term (Reid, 2017).
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| The Great Green Wall. Source: Opengiving.org |
To put afforestation into perspective, one needs to take current deforestation into account.
Around 13 million ha are deforested annually; most of them in tropical regions where net sink contributions of forests are the largest (combined subtropical forests store around 550 Gt of Carbon) (Chakravarty et al., 2012). In practical terms; approximately 15 billion of the existing 400 billion trees are logged every year, according to a 2014 NASA study (estimations vary drastically though).The incentives to (often illegally) convert forest to agriculture are still high since demand for land is growing. Here, a driver is insufficient management - only 6% of forests in developing countries are considered sustainably managed. Politically, in the light of aspects such as food security and population growth, it is questionable how much land can be reverted or transformed to forestry areas (whereas the WWF, for instance, argues, that another 600 billion trees could be planted on 'unwanted' space). Ultimately, without effective conversation and sustainable management schemes of existing forests afforestation efforts are nice-to-have but lack mitigation effectiveness.
In the larger context of geoengineering, a major upside of SRM in comparison to CDR is that it involves far fewer risks. This comes at the price of slower mitigation.The severity level of both the discourse and research on geoengineering highlight the urgency to act and possibly also the failure of current political priorities.
More on trees? Have a look at this blog from Tom - he takes a very close look at the Amazon Rainforest during this term.
Around 13 million ha are deforested annually; most of them in tropical regions where net sink contributions of forests are the largest (combined subtropical forests store around 550 Gt of Carbon) (Chakravarty et al., 2012). In practical terms; approximately 15 billion of the existing 400 billion trees are logged every year, according to a 2014 NASA study (estimations vary drastically though).The incentives to (often illegally) convert forest to agriculture are still high since demand for land is growing. Here, a driver is insufficient management - only 6% of forests in developing countries are considered sustainably managed. Politically, in the light of aspects such as food security and population growth, it is questionable how much land can be reverted or transformed to forestry areas (whereas the WWF, for instance, argues, that another 600 billion trees could be planted on 'unwanted' space). Ultimately, without effective conversation and sustainable management schemes of existing forests afforestation efforts are nice-to-have but lack mitigation effectiveness.
In the larger context of geoengineering, a major upside of SRM in comparison to CDR is that it involves far fewer risks. This comes at the price of slower mitigation.The severity level of both the discourse and research on geoengineering highlight the urgency to act and possibly also the failure of current political priorities.
More on trees? Have a look at this blog from Tom - he takes a very close look at the Amazon Rainforest during this term.
Do you think this will be effective soon enough?
ReplyDeleteHi Jemima, and welcome around! That is good question - primarily it appears that reducing the amount of deforestation is crucial for immideate mitigation. Planting trees, as Agness underneath rightly remarked are a great investment in the future. After all however, afforestation is one aspect in the greater arena of required action. I hope this helped, Luisa
DeleteSure trees can save a lot.
ReplyDeleteYes, Agness, the certainly can! And also, an aspect I find particularily interesting, they can act as motors for local communities - and enhance both organic and economic growth.
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