Land Use Effects on Climate: Current State, Recent Progress, and Emerging Topics

Purpose of Review As demand for food and fiber, but also for negative emissions, brings most of the Earth’s land surface under management, we aim to consolidate the scientific progress of recent years on the climatic effects of global land use change, including land management, and related land cover changes (LULCC). Recent Findings We review the methodological advances in both modeling and observations to capture biogeochemical and biogeophysical LULCC effects and summarize the knowledge on underlying mechanisms and on the strength of their effects. Recent studies have raised or resolved several important questions related to LULCC: How can we derive CO2 fluxes related to LULCC from satellites? Why are uncertainties in LULCC-related GHG fluxes so large? How can we explain that estimates of afforestation/reforestation potentials diverge by an order of magnitude? Can we reconcile the seemingly contradicting results of models and observations concerning the cooling effect of high-latitude deforestation? Summary Major progress has been achieved in understanding the complementarity of modeling, observations, and inventories for estimating the impacts of various LULCC practices on carbon, energy, and water fluxes. Emerging fields are the operationalization of the recently achieved integration of approaches, such as a full greenhouse gas balance of LULCC, mapping of emissions from global models to country-reported emissions data, or model evaluation against local biogeophysical observations. Fundamental challenges remain, however, e.g., in separating anthropogenic from natural land use dynamics and accurately quantifying the first. Recent progress has laid the foundation for future research to integrate the local to global scales at which the various effects act, to create co-benefits between global mitigation, including land-based carbon dioxide removal, and changes in local climate for effective adaptation strategies.

The impact of the COVID-19 enforced lockdown and fiscal package on the South African economy and environment: a preliminary analysis

This paper offers a quantitative assessment of the impacts of the COVID-19 pandemic-induced lockdown and government fiscal plan, containing ‘green’ elements on the economy and the environment of South Africa. The analysis uses a dynamic computable general equilibrium model operationalised using a social accounting matrix coupled with a greenhouse gas balance and emissions data. We find that while the economy is harshly impacted by the pandemic in the short term, the government fiscal package ameliorates and cushions the negative effects on poor households. Importantly, an adaptation of the fiscal package towards a ‘greener’ policy achieves the same economic outcome and reduces unemployment. Carbon dioxide emissions decrease in the short run due to economic slowdown. This improvement persists until 2030. These results can be used as decision support for policy makers on how to orient the post COVID-19 policies to be pro-poor and pro-environment, and thus, ‘build back better and fairer’.

Greenhouse Gas Balance of Sphagnum Farming on Highly Decomposed Peat at Former Peat Extraction Sites

For two years, we quantified the exchange of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) at two different large-scale Sphagnum farming sites. At both, peat extraction left a shallow layer of highly decomposed peat and low hydraulic conductivities. One site was characterized by preceding multi-annual inundation and irrigated by ditches, while the other one was inoculated directly after peat extraction and irrigated by ditches and drip irrigation. Further, GHG emissions from an irrigation polder and the effect of harvesting Sphagnum donor material at a near-natural reference site were determined. GHG mitigation potentials lag behind the results of less decomposed sites, although our results were also affected by the extraordinary hot and dry summer 2018. CO2 exchanges ranged between -0.6 and 2.2 t CO2-C ha−1 y−1 and were mainly influenced by low water table depths. CH4 emissions were low with the exception of plots with higher Eriophorum covers, while fluctuating water tables and poorly developing plant covers led to considerable N2O emissions at the ditch irrigation site. The removal of the upper vegetation at the near-natural site resulted in increased CH4 emissions and, on average, lowered CO2 emissions. Overall, best plant growth and lowest GHG emissions were measured at the previously inundated site. At the other site, drip irrigation provided more favourable conditions than ditch irrigation. The size of the area needed for water management (ditches, polders) strongly affected the areal GHG balances. We conclude that Sphagnum farming on highly decomposed peat is possible but requires elaborate water management.

Greenhouse gas balance of open peatlands is globally governed by soil water content and archaeal abundance

<p>There is a general consensus that peatlands are the source of about 10% of the global CO<sub>2</sub>, CH<sub>4</sub> and N<sub>2</sub>O greenhouse gas (GHG) emissions. Yet, our knowledge about underlying processes and environmental factors that regulate the GHG are limited. Here, we found that the GHG balance of CO<sub>2</sub>, CH<sub>4</sub> and N<sub>2</sub>O in 48 open peatland sites on five continents can be predicted by a model that incorporates soil water content (SWC) and archaeal abundance. We used our global database (2011–2019) on peat characteristics and field-measured soil respiration (ER), CH<sub>4</sub> and N<sub>2</sub>O emissions. Furthermore, we used the gross primary productivity (GPP) dataset by Running, Mu & Zhao (2015) on the basis of satellite data from the Moderate Resolution Imaging Spectrometer (MODIS) sensors alongside the ER to derive net ecosystem exchange (NEE) of carbon. The GHG balance follows SWC along a bell-shaped curve and increases with archaeal abundance and decomposition rate of peat-forming plant species. Thus, the net GHG emission peaks at intermediate SWC. These factors combined explains 61.9% (adjusted R<sup>2</sup> = 0.587) of GHG balance and most of this variance is made up by the NEE of carbon (adjusted R<sup>2</sup> = 0.97).</p>

Energy landscapes resulting from climate protection goals – a GIS-based approach to carbon neutrality

<p>To date, the spatio-temporal patterns of renewable energies brought about by a deployment that corresponds to internationally agreed climate protection goals, have been neither exactly analysed nor visualised. It is also unknown what land uses would be incorporated into these new energy landscapes due to a lack of spatial restrictions, and what social conflicts these land use changes may give rise to. Moreover, the extent to which existing land use, which is the product of a capitalist order, affects the achievement of a carbon-neutral society, has not been grasped at all. There is no knowledge about the feasibility of altering spatial restrictions for renewable energies in order to identify alternative spatial patterns of sustainable energy transition. Our objective is therefore to model and visualise a regional energy landscape whose greenhouse gas balance in the electricity sector corresponds to the target of the UN Climate Conference. The study provides a detailed analysis of the landscape transformations in rural spaces that would be caused if those forces which strive to link the energy transition to the values of the Paris Agreement were to win through. It is revealed that a precise alignment of the expansion of renewable energies with international climate protection targets would strongly mechanise rural areas and significantly transform their land use patterns.</p>