Bio-geoengineering to increase crop albedo

Industry

Agriculture landscape with small villages and forests in Baden Würtemberg, Germany

Surface albedo has a significant impact on global climate (Zhang et al. 2022). Plants play an important role in this. Matthews et al. (2003), for example, estimate that the spread of agriculture has led to a global cooling of around 0.17°C, as agricultural crops tend to have a higher albedo than wild vegetation (Monteith and Unsworth 1990).

The term Bio-geoengineering is used in several different ways related to the modification of living organisms (see for instance its usage by Peacock, 2015, and Reindeer management elsewhere in this report). Bio-geoengineering has for example been linked to the idea to increase the capabilities of peatlands to absorb carbon (Freeman et al. 2012), and to the aim to increase precipitation (Branch and Wulfmeyer 2019). However, here it refers to the idea to increase land surface albedo by growing higher-albedo plants, for example: the selection for broader leaves in trees (Ridgwell et al. 2009). To achieve this, the planting of already existing variants of a species or close relatives could already suffice, although gene editing might also be an option (Ridgewell et al. 2009). The topic has many links to other forms of surface albedo management (see Land Management and reindeer herding). Bio-geoengineering could be especially important when considering biofuels because the large-scale usage of forest harvesting (Bright et al. 2011) or cultivation of specific crops (Cai et al. 2016; Abraha et al. 2021) can have significant albedo effects.

Technological Readiness Level (TRL)

Medium 2

Crops have always been selected for specific purposes in agriculture, and Bio-geoengineering could be seen as adding one more trait to a list of desired qualities. Ridgewell et al. (2009) say that opposed to other SRM measures, the infrastructure is already in place and relatively easily operationable. However, there have not been enough focussed studies into the topic to give clarity on the potential readiness of Bio-geoengineering, which would in any case be highly case dependent.

Because the climate effect of plants can be highly complex and multiple and would have to be carefully analyzed so as not to have detrimental side-effects. As is the case for agriculture as a whole, it is also clearly required that such schemes be viable under a warming climate and increasingly high temperature extremes (Batissi and Naylor, 2009). Although Ridgewell et al (2009) and Singarayer and Davies-Barnard, 2012 stress that such practices need not negatively affect food yields, Genesio et al. (2020) describe an experiment with an albedo enhancing soy bean variant that would however reduce overall yields.

Technological Readiness Level (TRL)

A technology with a TRL of 4-6: TRL 4 – validated in lab; TRL 5 – validated in relevant environment; TRL 6 – demonstrated in relevant environment

Scalability

Medium 2

A large part of the global land surface area is taken up for agricultural purposes, which has a huge climate impact, so already slight modifications of surface albedo could potentially be very impactful (Liu et al, 2022). However, there are high uncertainties around the feasibility of Bio-geoengineering and its fit within global agricultural systems.

Scalability

Physically somewhat scalable; linear efficiency

Timeliness for near-future effects

Medium 2

Sometimes different varieties of the same crop species exist, which could allow for a speedy implementation by just switching variants.

Timeliness for near-future effects

Implemented in time to make some difference, although questionable

Northern + Arctic potential

Low 1

As stated above, Bio-geoengineering can have significant regional effects. Sieber et al (2022) field trial and satellite observation study found significant radiative forcing reduction potential for different kinds of agricultural crops in Northern Europe. Model studies found the effects of their global application were most pronounced in the Northern regions. Ridgewell et al. (2009) and Singarayer et al. (2009) show that cooling in their studies was most pronounced in Northern hemisphere Eurasia and America, and that large-scale implementation could even slightly delay Arctic sea-ice retreat. Irvine et al (2011) model study equally shows cropland geoengineering led to slight increases in sea ice thickness and recovery, and in snow depth.

However, it is not clear if the northern and Arctic regions are best suited for the application of Bio-geoengineering. Smoliak et al (2022) for example find that the highest potential for surface-based albedo interventions is clearly in the tropics and subtropics. Because of the prominence of forestry in the northern regions, this would partially hang together with findings from forestry management (see Forest management and Land management). Moreover, since Northern and Arctic regions are mostly covered by snow during winter season, any kind of land mitigation strategies should be carefully investigated as they might interfere with the effect of winter albedo (Bright et al, 2015).

Northern + Arctic potential

No noticeable extra positive effect beyond the global average; technology is unsuited to the Arctic

Global potential

Medium 2

Although the global potential for albedo surface management is significant Smoliak et al (2022), and can be important for climate mitigation strategies (Zhang et al, 2022), it is generally accepted that effects would be mostly regional. In the estimates of Lenton and Vaughan (2009) the global forcing potential when applied to all the world's grasslands would be −0.51 W m−2, and Irvine et al (2011) model study shows a maximum global cooling of 0.23°C.

The local effects could however be significant, as Genesio et al. (2020) described their experimental results that the introduction of a soybean mutant reduced local radiative forcing by −4.1 W/m-2. Liu et al (2022) also found that the potential impact of surface albedo management on the Canadian prairies could be significant, and in CO2 equivalent terms 'comparable to that due to soil carbon sequestration.’ Smoliak et al (2022) therefore urge that it should be explored where surface albedo could achieve cost-effective climate positive effects, and disagree with the simple dismissal of the measure because it is too expensive and inefficient on a global scale. This is confirmed by case studies, like Carrer et al (2018) who found that strategically planted cover crops, which increase albedo of dark soil, 'may mitigate up to 7% of the human-induced GHG agricultural emissions per year'. Vendig et al (2023) moreover found that the use of cover crops might be especially promising as it both increased soil carbon levels and increased crop yields.

Global potential

Statistically detectable impacts

Cost - benefit

Low 3

Ridgwell et al (2009) claim that Bio-geoengineering would be relatively low cost in comparison to other measures. This is echoed by Singarayer and Davies-Barnard (2012) and Nogués and Azcón-Bieto (2013), who even suggest it might therefore be appealing to developing countries, and could even bring economic opportunities. However, costs would likely be highly crop and region dependent.

Cost - benefit

Low investment cost compared to the avoided damage cost (e.g., a few %) and/or inexpensive relative to other measures with similar impact

Environmental risks

Medium 2

Although this would depend per species, it seems likely that major changes in biota could have environmental impacts - as does farming. Ridgewell et al (2009) study for example suggests potential effects of global precipitation patterns by large-scale deployment. Ridgewell et al (2009) and Smoliak et al (2022) however note that associated risk would be minor in comparison to other SRM measures.

Environmental risks

More widespread and possibly regional impacts that extend beyond the immediate solution deployment location

Community impacts

Neutral 2

Agriculture is not a common occupation in indigenous Arctic communities. Nogués and Azcón-Bieto (2013) suggest cheap options might be appealing to developing countries, and could even bring economic opportunities. However this is largely unstudied, and since bio-geoengineering would involve changes in land and plant coverage, it is likely to have at least some effects on surrounding communities and ecosystems.

Community impacts

Unnoticeable or negligible positive or negative effects

Ease of reversibility

Easy 3

Farmers change crops fairly often in some regions (e.g. China), but much slower in others (e.g. parts of Africa).

Ease of reversibility

Easily reversible naturally

Risk of termination shock

Low 3

Ridgewell et al (2009) claim that bio-geoengineering does not hold the risk of termination shock that other SRM measures do.

Risk of termination shock

Low or insignificant termination shock or damage

Legality/governance

High 3

Smoliak et al (2022) note that bio-geoengineering is not as controversial as other SRM and relatively low risk. Implementation would therefore likely not be subject to strict restrictions, and mainly need to conform to regular national regulations.

Legality/governance

Currently legal to deploy, with governance structures in place to facilitate it and/or financial incentives to develop it

Scientific/media attention

Medium 2

Biogeoengeering is mentioned in reports and the subject of some studies, although it is not as broadly covered as other albedo modification schemes (NASEM, 2015; Smoliak et al, 2022). Zhang et al. (2022) however note that their literature review showed that research into surface albedo increased since 2008 and that ‘[r]ecently, increasing attention has been dedicated to human-induced albedo variances’, and Liu et al (2022) equally note that they observe a recent increase in attention for the importance of surface albedo changes by land management practices.

Scientific/media attention

Some attention within the scientific community, including published research and funding programmes; some media attention; some commercial interest

References

Abraha, M.; Chen, J.; Hamilton, S.K.; Sciusco, P.; Lei, C.; Shirkey, G.; Yuan, J.; Robertson, G.P. Albedo-Induced Global Warming Impact of Conservation Reserve Program Grasslands Converted to Annual and Perennial Bioenergy Crops. Environ. Res. Lett. 2021, 16, 84059. https://doi.org/10.1088/1748-9326/ac1815

Battisti DS, Naylor RL (2009) Historical Warnings of Future Food Insecurity with Unprecedented Seasonal Heat. Science 323: 240-244. https://doi.org/10.1126/science.1164363

Branch, O., & Wulfmeyer, V. (2019). Deliberate enhancement of rainfall using desert plantations. Proceedings of the National Academy of Sciences, 116(38), 18841-18847. https://doi.org/10.1073/pnas.1904754116

Bright, R.M.; Stromman, A.H.; Peters, G.P. Radiative Forcing Impacts of Boreal Forest Biofuels: A Scenario Study for Norway in Light of Albedo. Environ. Sci. Technol. 2011, 45, 7570–7580. https://doi.org/10.1021/es201746b

Bright, R. M., Zhao, K., Jackson, R. B., & Cherubini, F. (2015). Quantifying surface albedo and other direct biogeophysical climate forcings of forestry activities. Global Change Biology, 21(9), 3246-3266. https://doi.org/10.1111/gcb.12951

Cai, H.; Wang, J.; Feng, Y.; Wang, M.; Qin, Z.; Dunn, J.B. Consideration of Land Use Change-Induced Surface Albedo Effects in Life-Cycle Analysis of Biofuels. Energy Environ. Sci. 2016, 9, 2855–2867. https://doi.org/10.1039/C6EE01728B

Carrer, D., Pique, G., Ferlicoq, M., Ceamanos, X., & Ceschia, E. (2018). What is the potential of cropland albedo management in the fight against global warming? A case study based on the use of cover crops. Environmental Research Letters, 13(4), 044030.

Freeman, C., Fenner, N., & Shirsat, A. H. (2012). Peatland geoengineering: an alternative approach to terrestrial carbon sequestration. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 370(1974), 4404-4421. https://doi.org/10.1088/1748-9326/aab650

Irvine, P. J., Ridgwell, A., & Lunt, D. J. (2011). Climatic effects of surface albedo geoengineering. Journal of Geophysical Research: Atmospheres, 116(D24). https://doi.org/10.1029/2011JD016281

Liu, J., Desjardins, R. L., Wang, S., Worth, D. E., Qian, B., & Shang, J. (2022). Climate impact from agricultural management practices in the Canadian Prairies: Carbon equivalence due to albedo change. Journal of Environmental Management, 302, 113938. https://doi.org/10.1016/j.jenvman.2021.113938

Nogués Mestres, S., & Azcón Bieto, J. (2013). Potential of local bio-geoengineering to mitigate dangerous temperature increases in a global warming scenario. Journal of Earth Science & Climatic Change, 2013, vol. 4, p. 143. https://doi.org/10.4172/2157-7617.1000143

Peacock, K. (2015, December). Biogeoengineering for the Anthropocene. In: AGU Fall Meeting Abstracts (Vol. 2015, pp. GC33A-1255). Available at: https://agu.confex.com/agu/fm15/webprogram/Paper66771.html [Accessed 22 July 2024]

Ridgwell, A., Singarayer, J. S., Hetherington, A. M., & Valdes, P. J. (2009). Tackling regional climate change by leaf albedo bio-geoengineering. Current biology, 19(2), 146-150. https://doi.org/10.1016/j.cub.2008.12.025

Sieber, Petra, Sepp Böhme, Niclas Ericsson, and Per-Anders Hansson. (2022). Albedo on cropland: Field-scale effects of current agricultural practices in Northern Europe. Agricultural and Forest Meteorology Volume 321, 108978. https://doi.org/10.1016/j.agrformet.2022.108978

Singarayer, J. S., & Davies-Barnard, T. (2012). Regional climate change mitigation with crops: context and assessment. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 370(1974), 4301-4316. https://doi.org/10.1098/rsta.2012.0010

Smoliak, B. V., Gelobter, M., & Haley, J. T. (2022). Mapping potential surface contributions to reflected solar radiation. Environmental Research Communications, 4(6), 065003. https://doi.org/10.1088/2515-7620/ac7a25

Singarayer, J. S., Ridgwell, A., & Irvine, P. (2009). Assessing the benefits of crop albedo bio-geoengineering. Environmental Research Letters, 4(4), 045110. https://doi.org/10.1088/1748-9326/4/4/045110

Vendig, I., Guzman, A., De La Cerda, G., Esquivel, K., Mayer, A. C., Ponisio, L., & Bowles, T. M. (2023). Quantifying direct yield benefits of soil carbon increases from cover cropping. Nature Sustainability, 1-10. https://doi.org/10.1038/s41893-023-01131-7

Zhang, X., Jiao, Z., Zhao, C., Qu, Y., Liu, Q., Zhang, H., ... & Cui, L. (2022). Review of Land Surface Albedo: Variance Characteristics, Climate Effect and Management Strategy. Remote Sensing, 14(6), 1382. https://doi.org/10.3390/rs14061382

Zhang, Z., Moore, J. C., Huisingh, D., & Zhao, Y. (2015). Review of geoengineering approaches to mitigating climate change. Journal of Cleaner Production, 103, 898-907. https://doi.org/10.1016/j.jclepro.2014.09.076

Related ideas

Oceans & marine

Re-oxygenating the Baltic

The deep waters in the Baltic are severely deoxygenated. Although the causes of the current state are complex, this is mainly a result of increased eutrophication from sewage and agricultural runoff from surrounding lands, which leads to extreme bioproductivity (Rolff et al. 2022). Some species manage to survive in the upper water layers, but many organisms living on the seafloor are severely impacted by the hypoxia, thereby influencing the health of a wide network of ecosystems and biochemical processes. There are attempts to reduce nutrient runoff into the Baltic (see for example: https://helcom.fi/baltic-sea-action-plan/). However, some argue these will be insufficient and argue for engineering solutions to the issue.

Sea ice & icebergs

Ice shields and “volcanoes”

Arctic sea ice extent has rapidly decreased over the last few decades, with most multi-year ice disappearing altogether. This has already had major effects on local communities and ecosystems. The disappearance of the relatively reflective sea ice also leads to a dramatic decrease of albedo in the Arctic and subsequent high energy uptakes by the darker water during the Arctic summers.

Old whale bone providing fertile conditions for vascular plants, Antarctic Peninsula

Industry

Biochar

The concentration of GHGs in the atmosphere will have to be stabilized or lowered to mitigate or even reverse current global warming. To achieve this, current GHG emissions need to be reduced. Such mitigation strategies will however take time to deploy, and some emission sources will be difficult to mitigate. Moreover, since current atmospheric levels are already having a major warming effect, negative emission or Carbon Dioxide Removal (CDR) measures that reduce the amount of GHGs in the atmosphere are an active topic of research.

Atmosphere / solar radiation

Arctic Marine Cloud Brightening

Roughly one-third of the incoming solar radiation is directly reflected back into space by the Earth’s atmosphere and surface albedo. Clouds play an important role in this, although their role is double as water droplets can also interfere with outgoing longwave radiation, thereby contributing to the greenhouse effect. Over open water clouds can make a particularly big difference as the albedo of the water is below 0.1, thereby absorbing most of the sun’s energy.

Ice sheets and glaciers

Glacier albedo increase

Up to 50% of the world’s glaciers are set to disappear this century, with many more at risk if emission reduction targets are not met (Rounce et al. 2023). The surface of many mountain glaciers has moreover significantly darkened due to a general increase in atmospheric black carbon and other kinds of aerosols.

Land-based measures

Reindeer herding

In many Arctic and Northern regions, domesticated or semi-domesticated reindeer (Rangifer tarandus) are the only large herbivores (Uboni et al. 2016). Reindeer play a crucial role in these ecosystems and in the livelihoods and traditions of multiple local and indigenous populations. In light of the major impact of climate change in the Arctic, the capacity of large herbivores to mitigate some of these effects is being explored. Herbivores can have different climate positive effects as they can reduce shrubification and slow ecosystem responses to climate change (Olofsson and Post 2018; Happonen et al. 2021), modify summer and winter surface albedo (te Beest et al. 2016), trample winter snow to thicken permafrost (Beer et al. 2020; Windirsch et al. 2022), and increase biomass and soil carbon sequestration (Ylänne et al. 2018; Ylänne et al. 2021; see also soil management).

Land-based measures

Agricultural soil management

Terrestrial carbon can be stored in biomass above or below the ground, and in soils themselves. Soil organic matter can form differently, and have different amounts of plant and microbial components depending on the availability of water (Cotrufo and Lavallee, 2022). The large amounts of the Earth that have been brought under cultivation over the past 12.000 years have significantly degraded soil carbon levels, and have released some 110 billion metric tons of carbon (Sanderman et al. 2017). Soil security and health is increasingly being recognised as essential for planetary health (Kopittke et al. (2022).

Nickel Smelters, Norilsk, Siberia, Russia

Industry

Carbon capture and storage

Both emission reductions and CDR measures that actively reduce carbon dioxide are essential to reduce the amount of GHGs in the atmosphere and mitigate the effects of climate change. However, some carbon emissions, especially in the industrial and energy sectors, will be difficult to fully decarbonise.