ATR-FTIR Study of Alaska Yellow Cedar Extractives and Relationship with Their Natural Durability

New approaches for assessing wood durability are needed to help categorize decay resistance as timber utilization shifts towards plantations or native forest regrowth that may be less durable than original native forest resources. This study evaluated attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy combined with principal component analysis (PCA) for distinguishing between groups of Alaska yellow cedar (Cupressus nootkatensis) wood for susceptibility to two decay fungi (Gloeophyllum trabeum and Rhodonia placenta) and the eastern subterranean termite (Reticulitermes flavipes). Alaska yellow cedar durability varied with test organisms, but the majority of samples were highly resistant to fungal and termite attack. Weight losses and extractives yield using sequential extractions (toluene:ethanol > ethanol > hot water) showed moderate to weak relationships. PCA analysis revealed limited ability to distinguish amongst levels of wood durability to all tested organisms. The absence of non-resistant samples may have influenced the ability of the chemometric methods to accurately categorize durability.

Where Has All the Carbon Gone?

Carbon is among the most abundant substances in the universe; although severely depleted in Earth, it is the primary structural element in biochemistry. Complex interactions between carbon and climate have stabilized the Earth system over geologic time. Since the modern instrumental CO2 record began in the 1950s, about half of fossil fuel emissions have been sequestered in the oceans and land ecosystems. Ocean uptake of fossil CO2 is governed by chemistry and circulation. Net land uptake is surprising because it implies a persistent worldwide excess of growth over decay. Land carbon sinks include ( a) CO2 fertilization, ( b) nitrogen fertilization, ( c) forest regrowth following agricultural abandonment, and ( d ) boreal warming. Carbon sinks in both land and oceans are threatened by warming and are likely to weaken or even reverse as emissions fall with the potential for amplification of climate change due to the release of previously stored carbon. Fossil CO2 will persist for centuries and perhaps many millennia after emissions cease. ▪ About half the carbon from fossil fuel combustion is removed from the atmosphere by sink processes in the land and oceans, slowing the increase of CO2 and global warming. These sinks may weaken or even reverse as climate warms and emissions fall. ▪ The net land sink for CO2 requires that plants have been growing faster than they decay for many decades, causing carbon to build up in the biosphere over and above the carbon lost to deforestation, fire, and other disturbances. ▪ CO2 uptake by the oceans is slow because only the surface water is in chemical contact with the air. Cold water at depth is physically isolated by its density. Deep water mixes with the surface in about 1,000 years. The deep water does not know we are here yet! ▪ After fossil fuel emissions cease, much of the extra CO2 will remain in the atmosphere for many centuries or even millennia. The lifetime of excess CO2 depends on total historical emissions; 10% to 40% could last until the year 40,000 AD. Expected final online publication date for the Annual Review of Earth and Planetary Sciences, Volume 50 is May 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Mexican agricultural frontier communities differ in forest dynamics with consequences for conservation and restoration

Forest regrowth is key to achieve restoration commitments, but we need to better understand under what circumstances it takes place and how long secondary forests persist. We studied a recently colonized agricultural frontier in southern Mexico. We quantified the spatiotemporal dynamics of forest loss and regrowth and tested how temporal variation in climate, and spatial variation in land availability, land quality and accessibility affect forest disturbance, regrowth and secondary forest persistence. Marqués de Comillas consistently exhibits more forest loss than regrowth, resulting in a net decrease of 30% forest cover (1991-2016). Secondary forest cover remained relatively constant while secondary forest persistence increased, suggesting that farmers are moving away from shifting cultivation. Temporal variation in disturbance and regrowth were explained by the annual variation in the Oceanic El Niño index combined with dry season rainfall and key policy and market interventions.Across communities the availability of high-quality soil overrules the effects of land availability and accessibility, but that at the pixel-level all three factors contributed to explaining forest conservation and restoration. Communities with more high-quality soils were able to spare land for forest conservation, and had less secondary forest that persisted for longer. Old forest and secondary forests were better represented on low-quality lands and on communal land. Both old and secondary forest were less common close to the main road, where secondary forests were also less persistent. Forest conservation and restoration can be explained by a complex interplay of biophysical and social drivers across time, space and scale. We warrant that stimulating private land ownership may cause remaining forest patches to be lost and that conservation initiatives should benefit the whole community. Forest regrowth and secondary forest persistence competes with agricultural production and ensuring farmers can access restoration benefits is key to success.

Comments: How Real Are Carbon Offsets?

Purchasing carbon offsets is a widespread means of attempting to meet carbon-reduction and net-zero emissions goals across many industries. Also widespread is the increasing scrutiny of the practice. How “real” are the offsets? How are they quantified and verified, and by whom? Purchasing carbon offsets, or carbon credits, is an option when a company’s efforts to eliminate its carbon emissions through mitigation methods fall short. The offsets are purchased through investments in projects that remove carbon from the atmosphere such as nature-based solutions (e.g., REDD, or reducing emissions from deforestation and forest degradation), negative-emission technologies (including carbon capture and storage [CCS] and bioenergy with CCS), and renewable energy. Here’s where the criticism arises: How is the amount of carbon captured by these projects measured? For example, how much carbon can a tree or forest handle? Are all trees equal in their carbon intake? The uncertainty and variability in carbon-accumulation rates is acknowledged in research studies that are attempting to provide quantification. A study published in Nature compiled more than 13,000 georeferenced measurements to determine the rates for the first 30 years of natural forest regrowth. A map showed more than 100-fold variation in rates across the globe and indicated that default rates from the Intergovernmental Panel on Climate Change may underestimate the rates by 32% on average and do not capture eightfold variation within ecozones. On the other hand, the study concluded that the maximum mitigation potential from natural forest regrowth is 11% lower than previously reported because of the use of overly high rates for locations of potential new forest. While the study was not intended to provide verification to be used in the carbon-offset market, it points to the difficulty in getting the numbers right. Third-party verifiers are casting light on the validity of offsets. Various organizations such as the Climate Registry and the American Carbon Registry (ACR) aim to set standards and best practices. In both the regulated and voluntary carbon markets, ACR says it “oversees the registration and verification of carbon-offset projects following approved carbon accounting methodologies or protocols and issues offsets on a transparent registry system.” In July, CarbonPlan, a nonprofit that analyzes climate solutions based on the best available science and data, rated BCarbon, a standard created by Rice University’s Baker Institute for Public Policy, as one of the best publicly available protocols for soil carbon offsets in the US. BCarbon, a nature-based mitigation system, aims to remove CO2 from the atmosphere and store it in soil as organic carbon. Based on independent verification and certification requirements, the credits under the system are issued for the removal of CO2 by photosynthesis and storage as carbon in soil. Landowners are eligible for storage payments. The Baker Institute said the approach could unlock the potential for removal, storage, and certification of upwards of 1 billion tons of CO2 and lead to the protection and restoration of hundreds of millions of acres of grassland. Scrutiny of carbon offsets is beneficial in this expanding carbon market. Verification and certification will serve to increase the trust of both buyers and sellers—and the public—in what will likely be a bridge toward longer-term solutions to reduce global carbon emissions. And getting the numbers right is essential.

Fire-derived phosphorus fertilization of African tropical forests

Central African tropical forests face increasing anthropogenic pressures, particularly in the form of deforestation and land-use conversion to agriculture. The long-term effects of this transformation of pristine forests to fallow-based agroecosystems and secondary forests on biogeochemical cycles that drive forest functioning are poorly understood. Here, we show that biomass burning on the African continent results in high phosphorus (P) deposition on an equatorial forest via fire-derived atmospheric emissions. Furthermore, we show that deposition loads increase with forest regrowth age, likely due to increasing canopy complexity, ranging from 0.4 kg P ha−1 yr−1 on agricultural fields to 3.1 kg P ha−1 yr−1 on old secondary forests. In forest systems, canopy wash-off of dry P deposition increases with rainfall amount, highlighting how tropical forest canopies act as dynamic reservoirs for enhanced addition of this essential plant nutrient. Overall, the observed P deposition load at the study site is substantial and demonstrates the importance of canopy trapping as a pathway for nutrient input into forest ecosystems.

Non-uniform tropical forest responses to the ‘Columbian Exchange’ in the Neotropics and Asia-Pacific

It has been suggested that Iberian arrival in the Americas in 1492 and subsequent dramatic depopulation led to forest regrowth that had global impacts on atmospheric CO2 concentrations and surface temperatures. Despite tropical forests representing the most important terrestrial carbon stock globally, systematic examination of historical afforestation in these habitats in the Neotropics is lacking. Additionally, there has been no assessment of similar depopulation–afforestation dynamics in other parts of the global tropics that were incorporated into the Spanish Empire. Here, we compile and semi-quantitatively analyse pollen records from the regions claimed by the Spanish in the Atlantic and Pacific to provide pan-tropical insights into European colonial impacts on forest dynamics. Our results suggest that periods of afforestation over the past millennium varied across space and time and depended on social, economic and biogeographic contexts. We argue that this reveals the unequal and divergent origins of the Anthropocene as a socio-political and biophysical process, highlighting the need for higher-resolution, targeted analyses to fully elucidate pre-colonial and colonial era human–tropical landscape interactions.

Widespread reforestation before European influence on Amazonia

An estimated 90 to 95% of Indigenous people in Amazonia died after European contact. This population collapse is postulated to have caused decreases in atmospheric carbon dioxide concentrations at around 1610 CE, as a result of a wave of land abandonment in the wake of disease, slavery, and warfare, whereby the attendant reversion to forest substantially increased terrestrial carbon sequestration. On the basis of 39 Amazonian fossil pollen records, we show that there was no synchronous reforestation event associated with such an atmospheric carbon dioxide response after European arrival in Amazonia. Instead, we find that, at most sites, land abandonment and forest regrowth began about 300 to 600 years before European arrival. Pre-European pandemics, social strife, or environmental change may have contributed to these early site abandonments and ecological shifts.

Global economic and diet transitions drove Latin American and Caribbean forest change during the first decade of the century.

Latin America and the Caribbean (LAC) contain more tropical high-biodiversity forest than the remaining areas of the planet combined, yet experienced more than a third of global deforestation during the first decade of the 21st century. While drivers of forest change occur at multiple scales, we examined forest change at the municipal and national scales integrated with global processes such as capital, commodity, and labor flows. We modeled multi-scale socioeconomic, demographic, and environmental drivers of local forest cover change. Consistent with LAC’s global leadership in soy and beef exports, primarily to China, Russia, the US, and the EU, national-level beef and soy production were the primary land use drivers of decreased forest cover. National level GDPs, migrant worker remittances, and foreign investment, along with municipal-level temperature and area, were also significantly related to reduced forest cover. This challenges forest transition frameworks, which theorize that rising GDP and intensified agricultural production should be increasingly associated with forest regrowth. Instead, LAC forest change was linked to local, national, and global demographic, dietary and economic transitions, resulting in massive net forest cover loss. This suggests an urgent need to reconcile forest conservation with mounting global demand for animal protein.