How to Estimate Emissions from Land Use Change

This blog post highlights the valuable role played by GIS layers in planning and complying with upcoming GHG reporting standards. New protocols will classify carbon released from land use changes as Scope 1 emissions, requiring stricter tracking.

There are several GIS layers (reviewed below) that can be used to estimate potential carbon emissions from biomass and soil carbon losses due to land development projects. While these layers may not be suitable for final reporting, they can be valuable for:

• Strategic planning: Identifying areas with high potential emissions and prioritizing mitigation efforts.
• Impact Assessment: Estimating the range of carbon emissions from projects.

These GIS layers, available in Esri's ArcGIS Online Living Atlas, have the potential to improve the ability of large businesses to plan for and comply with upcoming regulations related to land use change emissions.

UNEP Above and Below Ground Biomass Carbon 

Two datasets represent above- and below-ground terrestrial carbon storage (tonnes (t) of C per hectare (ha)) for the entire globe (2010).  The first layer layer estimates total biomass (i.e. plant parts such as roots, leaves, trunks) whereas the second layer includes soil organic carbon (SOC) and is therefore weighted to show the contribution of peat and permafrost-contained regions.  Both layers support direct analysis in GIS software.    

Left: First dataset shows plant biomass with large concentrations of C in the world's forests.  Right: Second dataset includes SOC and shows the large amounts of C in the world's arctic peat and permafrost.

USFS Predominant Major Forest Carbon Pools of the Continental United States

This layer layer depicts the predominant major forest carbon (short tons per pixel) pools of the Continental United States. The layer used USFS Forest Inventory & Analysis plot data and Landsat 8 Operational Land Imager scenes as inputs to an ecological climate model to estimate Live, Dead, and Organic Soil carbon pools.  However, the data is somewhat difficult to analyze because each pool is in separate raster image bands, and because the metric reported is short tons per pixel, where the pixel size varies across the map based on Web Mercator projection.  

USFS offers a faster and easier to use layer called CONUS Total Forest Carbon 2018, which provides short tons Carbon per pixel summed across all 8 individual carbon pools.  

Around Prescott, AZ the pixel size is 80 by 80 ft, so each pixel value must be multiplied by 6.8 to get tons per acre.  It looks like most of the pixels show a carbon pool of 30-36 tons/acre in this area.

To compare this layer with the UN layers mentioned above, it is necessary to convert US tons to metric tons and acres to hectares.  Overall this yields a correction factor of 2.24 to get from tons/acre to metric tons/hectare.  This yields a range of 67-80 metric tons/hectare carbon based on the USFS layer.  The UN Total Biomass layer estimates anywhere from 38-50 metric tons/hectare, while the UN layer that adds in SOC estimates 120-160 metric tons/hectare.  It seems that the USFS map estimates carbon pools in between these two ranges.

Northern AZ pine forests viewed in the USFS Forest Carbon layer.  It is not always clear how to interpret this data.

Land Development Releases Greenhouse Gases

Land use change releases stored carbon and should be counted under Greenhouse Gas (GHG) reporting.  

Example of a wildflower meadow (left) that was bulldozed to create a parking lot (right). This land use change results in direct emissions of stored soil carbon and plant biomass, as well as continuing opportunity costs: the meadow can no longer accumulate sequestered carbon. If this land is owned by the developing company, this would count as Scope 1 Emissions under GHG reporting requirements.

New GHG reporting standards for land use change are due to be finalized in 2024. According to these new standards,

"Companies shall:

-Account for land use change emissions from land carbon stock decreases across all carbon pools (biomass, soil organic carbon and dead organic matter).

-Account for and report direct land use change (dLUC) emissions or statistical land use change (sLUC) emissions in scope 1, scope 2, and scope 3."

This is important because, according to the IPCC AR6 (2023), land use change accounts for approximately 15% of anthropogenic emissions.  Interestingly, the parts of the land and ocean that have not been developed by humans still absorb 30% of our emissions.  As we degrade more and more land and water, the Earth loses this buffering capacity, in addition to the extra emissions created from land use change.

Saving Biodiversity is Essential to Stop Global Warming

This simple message -that we can't save the Earth without saving the actual physical, water-and-soil-and-plant Earth- needs to be said and re-said until everyone understands.  

We've been disappointed by the scientists, leaders, and especially the "environmentalists" (like Sierra Club, Audubon, Union of Concerned Scientists, etc...) who have decided to advocate for industrial "renewable" energy as the only solution.  They've looked at the massive environmental destruction required to mine, manufacture, and construct solar and wind farms and connecting transmission lines - and said yes, we must destroy the world to save the world.

However, there is hope within the current system.  The push to save biodiversity, while sometimes sidelined, has significant support in the COP15 agreement.  That agreement, and related work by TNFD, will have to be considered, often for the very first time, by every company and gov't with sustainability disclosures.  

Even the IPCC addresses the importance of land use - the latest AR6* still shows global photosynthesis absorbing net carbon every year, despite human land-use change continuing to destroy that literal lifeblood of our planet.  

All numbers are gigatonnes of Carbon.  Image Source: Hillis, David.  Life: The Science of Biology.  Textbook published 2020 by Macmillan Higher Ed.  

According to the diagram above, net plant growth (photosynthesis - respiration) stores 3 gigatonnes/year of carbon, offsetting almost 1/3 of the yearly emissions from fossil fuels (9.5 gigatonnes/year).  However, human-altered land use and human-caused fires emit another 2 gigatonnes/year of carbon to the atmosphere.   A gigatonne is about twice the weight of all the humans in the world. (Source: https://energyeducation.ca/encyclopedia/Gigatonne)

Also, the upcoming (in 2024) standards for including land use change in Scope 1/2/3 emissions reporting will explicitly tie real environmental destruction (clearing forests, bulldozing farmland) to the statistics that accountants love to worship, total tons of carbon emitted.  Now developers (even of renewable energy) can't ignore the cost that continued industrialization has to the Earth's life-giving ability to absorb and store carbon.  

Source: https://ghgprotocol.org/land-sector-and-removals-guidance

Hopefully, with all of these connections being made, people will finally start to give credit where credit is due, and give thanks to our beautiful, fragile planet for all it does for us.

*IPCC overview diagrams of global carbon sinks and sources:

 AR6 (2023) : https://www.ipcc.ch/report/ar6/wg1/figures/chapter-5/figure-5-12/

AR5 (2013) overview: https://www.researchgate.net/figure/Simplified-schematic-of-the-global-carbon-cycle-IPCC-2013-Numbers-represent-carbon_fig4_281185559

AR4 (2007) overview: https://www.researchgate.net/figure/The-global-carbon-cycle-boxes-are-carbon-pools-and-the-arrows-the-fluxes-between-them_fig2_255642401

Carbon offset controversy

 

https://carbon180.medium.com/in-search-of-carbon-removal-offsets-42abf71b3ccc

https://forestpolicypub.com/2020/12/10/bloomberg-green-on-the-nature-conservancy-and-meaningless-carbon-offsets/

Regenerative Agriculture Controversy?

 https://www.wri.org/blog/2020/05/regenerative-agriculture-climate-change

https://agfundernews.com/opinion-where-the-world-resources-institute-got-it-wrong-about-regenerative-agriculture.html

https://undark.org/2020/01/31/podcast-43-regenerative-agriculture/

Cremation is a major source of black carbon

Original Press Release.  News article.  Burning is central to human life, and many human after-lifes.  Unfortunately, smoldering fires release soot and toxic compounds which degrade air quality, accelerate snow melt, and warm the climate.

Current data shows biosphere carbon uptake holding steady

One of the biggest questions for ecosystem scientists is the degree to which terrestrial and marine ecosystems  can continue to sequester carbon in the face of continuing human emissions of CO2 and accompanying global climate change.

This is one of the best (i.e. easiest to interpret) graphs to show that the fraction of emitted CO2 remaining in the atmosphere (i.e. not sequestered) has held steady at around 50% for the last 40+ years (purple line, "Airborne Fraction").  Data Sources: Fossil fuel CO2 emissions - Land use CO2 emissions -  Airborne CO2 levels Graph by Willis Eschenbach.

Similar conclusions were reached by the National Oceanic and Atmospheric Administration’s Earth System Research Laboratory in Boulder, Colorado last year.

Timber Harvest Effect on Soil

The overall effect is a small loss in total soil carbon; both total carbon content and concentration decrease in the "forest floor," but not in the surface or deep mineral soils. 

Black dots are total carbon; white dots are carbon concentration.

The decrease in total forest floor carbon is greater in hardwood forests, although there is some evidence that it takes longer to rebound in conifer forests because of their lower litter production.

Citation:
Nave LE, Vance ED, Swanston CW, Curtis PS. Harvest impacts on soil carbon storage in temperate forests. Forest Ecology and Management. 2010;259(5):857–866.

Variable Land Carbon Sink

b, CO2 emissions from fossil fuel combustion and cement production, and from LUC. c, Land CO2 sink (negative values correspond to land uptake). d, Ocean CO2 sink (negative values correspond to ocean uptake).

Le Quéré C, Raupach MR, Canadell JG, Marland G, others. Trends in the sources and sinks of carbon dioxide. Nature Geoscience. 2009;2(12):831–836.


"An increasing total airborne fraction implies that total sinks are increasing more slowly than total emissions, so that sinks are not keeping pace with emissions.

The CO2 growth rate also varies strongly at interannual (1 to 10 y) time scales, through mainly biophysical mechanisms. Fluctuations in CO2 growth rate correlate with the El-Nino-Southern-Oscillation (ENSO) climate mode (Keeling and Revelle, 1985; Keeling et al., 1995; Jones and Cox, 2005), because the terrestrial carbon balance in tropical regions is tilted from uptake to release of CO2 during dry, warm El-Ni ˜ no events (Zeng et al., 2005; Knorr et al., 2005).

Volcanic events are also significant: the CO2 growth rate decreased for several years after the eruption of Mt. Pinatubo in June 1991 (Jones et al., 2001), probably because of increased net carbon uptake by terrestrial ecosystems due to higher diffuse solar radiation (Gu et al., 2003) and cooler temperatures (Jones and Cox, 2001) caused by volcanic aerosols."
1. Raupach MR, Canadell JG, Le Quéré C. Anthropogenic and biophysical contributions to increasing atmospheric CO2 growth rate and airborne fraction. Biogeosciences. 2008;5(6):1601–1613.

Carbon Tracker


Fig. 1. A demonstration of how carbon flux indices [GSNF, growing season net flux; DSNF, dormant season net flux; AMP, amplitude (|DSNF – GSNF|); NCF, net carbon flux (GSNF + DSNF)] are calculated. Any month for which the net carbon flux is negative is included in the GSNF (open vertical bars). Any month for which the net carbon flux is positive is included in the DSNF (filled vertical bars). Mean 2000–2008 fluxes shown for boreal North America (a) southern Africa (b) and tropical Asia (c).

GURNEY KR, ECKELS WJ. Regional trends in terrestrial carbon exchange and their seasonal signatures. Tellus B.

Fig. 2. Comparison of decadal mean net carbon flux for individual land regions. Black cross symbols (X) denote the mean of 13 TransCom 3 models, open circle symbols (O) denote mean of the three S07 TransCom 3 models, individual model estimates within the S07 average are denoted by a filled square, circle and triangle. Vertical error bars represent the total 1σ flux uncertainty (quadrature sum of model spread and the root mean square of individual model posterior uncertainty) associated with the mean of the 13 TransCom 3 models. (c) 2000–2008 mean net carbon flux.

Terrestrial Fertilization to Sequester CO2?

One of the main uncertainties in the global carbon cycle is measuring the amount of carbon bound up in ecosystems such as forests and grasslands. This Net Ecosystem Production (NEP) converts CO2 to plant material, detritus, and some animals. Most escapes back to the atmosphere as respired CO2, but some is sequestered in soil organic matter and trees.

Most ecosystems are Nitrogen limited because fertilization with nitrogen increases NEP. Interestingly, many ecosystems are already fertilized by Nitrogen deposition from drifting clouds of various nitrogen compounds emitted by urban areas, industry, and agriculture.

Nitrogen deposition increases productivity and decreases respiratory losses from decomposition (Hogberg). But how much? And how much is too much? Natural vegetation may be satiated/saturated with a low quantity of nitrogen, and any more would begin acidifying the soil, killing plants and washing away to pollute the watersheds.

Magnani et al attempt to answer some of these questions and measure the size of the "The human footprint in the carbon cycle of temperate and boreal forests" of Europe. They find that the amount of nitrogen deposited in European forests confers a huge increase in fertility; they find no sign of a decrease due to Nitrogen saturation.

However, their findings rested on a number of unpublished studies, and a flurry of correspondence questioned their main conclusions. De Shrivjer et al point out that just because NEP continues to increase with increasing Nitrogen deposition, this doesn't mean that the forest ecosystems aren't loosing nitrogen as runoff. Indeed, it makes sense that at very high applications of fertilizer an increasing fraction would be wasted. Many farmers have to contend with the problem that, beyond a certain point, a doubling of Nitrogen fertilizer may confer only an incremental increase in crop productivity, while vastly increasing the amount of Nitrogen that washes off.

de Vries present a more central problem in Magnani et al's results: according to Magnani's data correlation, for every unit of Nitrogen applied to European forests, 470 units of carbon are sequestered. Yet the only plant material with a C:N ratio that high is pure xylem wood, and it seems unlikely that all of the deposited nitrogen is being used to grow tree stems. Furthermore, de Vries et al find that Magnani et al failed to control for a range of other variables that could affect forest NEP. de Vries reanalyze that portion of Magnani's data that is publicly available and find a more plausible -- and vastly reduced -- C:N ratio of 20 to 40 (20-40 units carbon for every unit nitrogen).

It doesn't end there, though. Magnani et al respond that they agree with De Shrivjer, but refute de Vries. Magnani point out differences between wet and dry deposition, to argue that their stoichiometric ratio is really closer to 175-225. They claim that this ratio is not implausible, even though it is much higher than actual forest fertilization experiments (Nadelhoffer). They explain this difference by suggesting that up to 70% of the actual nitrogen deposited is absorbed by leaves, whereas the forest fertilization experiments applied nitrogen to the soil. (Nadelhoffer).

{[It is not clear to me what the consensus is on how much nitrogen can be absorbed by the canopy, or why wet versus dry deposition matters. }

News and Views: Hogberg P. Environmental science: Nitrogen impacts on forest carbon. Nature. 2007 June 14;447(7146):781-782.

Original Paper: Magnani F, Mencuccini M, Borghetti M, Berbigier P, Berninger F, Delzon S, Grelle A, Hari P, Jarvis PG, Kolari P, et al. The human footprint in the carbon cycle of temperate and boreal forests. Nature. 2007 June 14;447(7146):849-851.

Questions: De Schrijver A, Verheyen K, Mertens J, Staelens J, Wuyts K, Muys B. Nitrogen saturation and net ecosystem production. Nature. 2008 February 14;451(7180):E1.

More Questions: de Vries W, Solberg S, Dobbertin M, Sterba H, Laubhahn D, Reinds GJ, Nabuurs G-J, Gundersen P, Sutton MA. Ecologically implausible carbon response? Nature. 2008 February 14;451(7180):E1-E3.

Response:Magnani F, Mencuccini M, Borghetti M, Berninger F, Delzon S, Grelle A, Hari P, Jarvis PG, Kolari P, Kowalski AS, et al. Magnani et al. reply. Nature. 2008 February 14;451(7180):E3-E4.

More Information: Nadelhoffer, K. J. et al. Nitrogen deposition makes a minor contribution to carbon sequestration in temperate forests. Nature 398, 145–148 (1999)

Follow Up: SUTTON MA, SIMPSON D, LEVY PE, SMITH RI, REIS S, Van OIJEN M, De VRIES WIM. Uncertainties in the relationship between atmospheric nitrogen deposition and forest carbon sequestration. Global Change Biology. 2008 September 1;14(9):2057-2063.

Intensive farming may ease climate change

"Land saved from cultivation offsets carbon emissions" Nature 465, 853 (2010)

This Nature News item reviews a paper published by Burney et al in PNAS entitled "Greenhouse gas mitigation by agricultural intensification." The article shows that agriculture today is more land-efficient than in 1960. Yet it has been interpreted to say that modern intensive industrial agriculture is better than organic. The authors should write a statement clarifying their work but they may not. The reason? The study, as written, is trivial, and only with the added implication is it interesting. But the implication is not true.

In addition to commiting the unforgivable sin of reasoning based on historical counterfactuals, the article presents a myopic and simplistic either-or argument rather than a systematic analysis of factors contributing to agricultural land use. The fact that 50% of all food produced is wasted strikes me as one area where adding efficiency could reduce the overall footprint of agriculture. Certainly the choice of which land to pave over (usually the most fertile agricultural land) and which land to convert to agriculture (eg primeval Amazonian rainforest) has been especially perverse and unnecessary. Furthermore, our society's choice of food is also not a given "quality of life" as the article assumes; rather, it is a socially constructed and contigent demand on land use. If Americans consumed more primary production (plants) and less secondary production (animals) we could vastly decrease our agricultural footprint.

Other issues could be raised, but these points show some of the many analytical failings of this article. Despite, or perhaps because of its unsupported thesis, it has also been extensively commented upon; the authoritative review of responses in here.