Playing with nature ...

The ability of plants to uptake CO2 from the atmosphere produced a focus on the potential of nature to geo-engineer the climate and mitigate future environmental change. The terrestrial biomass that have been examined specifically for geo-enigineering purposes are afforestation, reforestation and biochar.

Reforestation: refers to the establishment of forest on land that had recent tree cover
Afforestation: refers to land that hasn't had tree cover or forest for a longer period of time

Anthropogenic deforestation has been recognised as a major contributor to global warming both due to the loss of future CO2 uptake and the release of sequestered CO2 that occurs when trees are cut down. Afforestation and reforestation processes are considered to be cheap and safe techniques, that ultimately achieve the end goal of CO2 uptake from the atmosphere. Globally deforestation is decreasing and reforestation and afforestation are increasing in some regions (see fig 1). Despite this, the impacts of deforestation remain, with large losses having taken place in tropical regions (FAO, 2013).

Effectiveness
Candall and Raupach (2008) state that reforestation has the potential to reduce atmospheric CO2 by 70-100ppm by 2100. This high figure offers promise, particularly when compared to the predicted reduction of 130ppm that would be caused by ocean iron fertilisation (discussed in my previous blog post). Unfortunately, a close inspection of the methods of the paper reveals this figure is deceiving as it assumes that complete reforestation is possible when actually it is not. Moreover, a reduction of 70-100ppm by 2100, be as it may a reduction of atmospheric CO2, is not a large enough reduction to reverse the effects of anthopogenic climate change.

Impacts
It has been demonstrated that only 9% of land surface would be biophysically suitable for reforestation and afforestation. However, more than half of this available land is used for agriculture and as a result not only food security would be compromised, there would be a high socioeconomic cost to afforestation and reforestation as farmers would lose labour as their are replaced by low labour forestry management (Zomer et al., 2008).

Afforestation and reforestation processes could also have hydrological impacts as runoff would be reduced and 'green vapour' flows would increase. In 2008 Trabucco et al., concluded that afforestation on 27% of suitable land would be affected by a 80-100% decrease in runoff, while 50% of suitable land could experience a reduction of 60%. In particular decreases were prevalent in drier, semi arid areas and in conversions from grasslands to subsistence agriculture. Consequently, reforestation and afforestation could potentially effect water resources and water management which is particularly significant given rising concerns over water scarcity. Moreover, the characteristics of suitable land also need to be considered as many areas deemed as suitable land may exhibit problems i.e. the human activities prior to and the mode of establishment for new trees.

Decreases in runoff in areas that are deemed suitable for reforestation and afforestation 

Increases in green vapour flows in areas deemed suitable for afforestation and reforestation 

A key factor that is overlooked in research on reforestation and afforestation is whether the processes are likely to be adopted. A study by Schirmer and Bull (2013) examined this in Australia and showed that widespread adoption requires designing afforestation so it (i) provides a range of socio-economic benefits that go beyond provision of income; (ii) minimises disruption to land management flexibility; and (iii) is compatible with landholder beliefs about appropriate use of agricultural land. 

Further to this, economic markets are also an important aspect to consider. In 2012, during the recovery from economic downturn, the market for industrial roundwood and sawnwood production increased by 6%, while wood panel production increased by 2% compared to 2011 in North America. The Asia-Pacific also increased its prominance as a producer and consumer of forest products, with China taking the lead. Sawnwood production in the region climbed by 11 percent and panels by 6 percent compared to 2011.

The importance of considering the range of perceptions of stakeholders involved in both the implementation of methods and also in the wider market is thus highlighted. Perhaps more significant is the suggestion that without changing perceptions towards a realization of the danger of deforestation and the benefits and ultimately adoption of reforestation and afforestation, research of the effectiveness of the methods is a futile task. Thus, if the method is adopted in the future to combat climate change then efforts to change perceptions will also be needed.