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

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.