scholarly journals Climate change and elevated CO<sub>2</sub> favor forest over savanna under different future scenarios in South Asia

Author(s):  
Dushyant Kumar ◽  
Mirjam Pfeiffer ◽  
Camille Gaillard ◽  
Liam Langan ◽  
Simon Scheiter

Abstract. South Asian vegetation provides essential ecosystem services to the region and its 1.7 billion inhabitants that are closely linked to its land-use forms and carbon storage potential. Yet, biodiversity is threatened by climate and land-use change. Understanding and assessing how ecosystems respond to simultaneous increases in atmospheric CO2 and future climate change is of vital importance to avoid undesired ecosystem change. A failure to react to increasing CO2 and climate change will likely have severe consequences for biodiversity and humankind. Here, we used the aDGVM2 to simulate vegetation dynamics in South Asia under RCP4.5 and RCP8.5, and we explored how the presence or absence of CO2 fertilization influences vegetation responses to climate change. Simulated vegetation under both RCPs without CO2 fertilization effects showed a decrease in tree dominance and biomass, whereas simulations with CO2 fertilization showed an increase in biomass, canopy cover, and tree height and a decrease in biome-specific evapotranspiration by the end of the 21st century. The model predicted changes in above ground biomass and canopy cover that trigger biome transition towards tree-dominated systems. We found that savanna regions are at high risk of woody encroachment and transitioning into forest. We also found transitions of deciduous forest to evergreen forest in the mountain regions. C3 photosynthesis dependent vegetation was not saturated at current CO2 concentrations and the model simulated a strong CO2 fertilization effect with the rising CO2. Hence, vegetation in the region will likely remain a carbon sink. Projections showed that the bioclimatic envelopes of biomes need adjustments to account for shifts caused by climate change and eCO2. The results of our study help to understand the regional climate-vegetation interactions and can support the development of regional strategies to preserve ecosystem services and biodiversity under elevated CO2 and climate change.

2021 ◽  
Vol 18 (9) ◽  
pp. 2957-2979
Author(s):  
Dushyant Kumar ◽  
Mirjam Pfeiffer ◽  
Camille Gaillard ◽  
Liam Langan ◽  
Simon Scheiter

Abstract. South Asian vegetation provides essential ecosystem services to the 1.7 billion inhabitants living in the region. However, biodiversity and ecosystem services are threatened by climate and land-use change. Understanding and assessing how ecosystems respond to simultaneous increases in atmospheric CO2 and future climate change is of vital importance to avoid undesired ecosystem change. Failed reaction to increasing CO2 and climate change will likely have severe consequences for biodiversity and humankind. Here, we used the adaptive dynamic global vegetation model version 2 (aDGVM2) to simulate vegetation dynamics in South Asia under RCP4.5 and RCP8.5, and we explored how the presence or absence of CO2 fertilization influences vegetation responses to climate change. Simulated vegetation under both representative concentration pathways (RCPs) without CO2 fertilization effects showed a decrease in tree dominance and biomass, whereas simulations with CO2 fertilization showed an increase in biomass, canopy cover, and tree height and a decrease in biome-specific evapotranspiration by the end of the 21st century. The predicted changes in aboveground biomass and canopy cover triggered transition towards tree-dominated biomes. We found that savanna regions are at high risk of woody encroachment and transitioning into forest. We also found transitions of deciduous forest to evergreen forest in the mountain regions. Vegetation types using C3 photosynthetic pathway were not saturated at current CO2 concentrations, and the model simulated a strong CO2 fertilization effect with the rising CO2. Hence, vegetation in the region has the potential to remain a carbon sink. Projections showed that the bioclimatic envelopes of biomes need adjustments to account for shifts caused by climate change and elevated CO2. The results of our study help to understand the regional climate–vegetation interactions and can support the development of regional strategies to preserve ecosystem services and biodiversity under elevated CO2 and climate change.


2020 ◽  
Author(s):  
Dushyant Kumar ◽  
Mirjam Pfeiffer ◽  
Camille Gaillard ◽  
Liam Langan ◽  
Carola Martens ◽  
...  

&lt;p&gt;South Asia is one of the world&amp;#8217;s most vulnerable regions to climate change and provides a home to approximately 1.7 billion people. South Asian vegetation is essential for ecosystem services, biodiversity and carbon storage in the region. Vegetation distribution and biome niches are likely to be severely altered by future climate change and rising atmospheric CO&lt;sub&gt;2&lt;/sub&gt; concentration. Assessing how ecosystems will respond to these changes is of vital importance. We used the aDGVM2 to simulate vegetation patterns of South Asia under RCP4.5 and RCP8.5. We found good agreement between observed and simulated biomass, height and potential vegetation maps.&amp;#160;&lt;/p&gt;&lt;p&gt;Model results show that large areas are susceptible to biome shift by the end of the 21st century. Woody encroachment is predicted in open savanna regions which are at high risk of transitioning into forest. We simulated vegetation under both scenarios with fixed CO&lt;sub&gt;2&lt;/sub&gt; concentration and found decreased tree dominance and biomass. Simulations under elevated CO&lt;sub&gt;2&lt;/sub&gt; concentrations predicted an increase in biomass, canopy cover, tree height and decrease in evapotranspiration. Changes in above ground biomass and canopy cover trigger biome shifts toward trees dominated the system. C3 vegetation is not saturated at current CO&lt;sub&gt;2&lt;/sub&gt; concentrations as the model simulated strong CO&lt;sub&gt;2&lt;/sub&gt; fertilization effect which will increase further with the rising CO&lt;sub&gt;2&lt;/sub&gt;. Although there is considerable uncertainty in the biome projections, the geographic patterns of biomes are generally consistent across the RCP4.5 and RCP8.5 scenarios. The results provide potential future trajectories of the response of South Asian vegetation to the climate change. The results will help to understand the regional climate-vegetation interaction and to develop regional strategies for biodiversity conservation to cope with climate change.&amp;#160;&lt;/p&gt;


2017 ◽  
Vol 14 (6) ◽  
pp. 1383-1401 ◽  
Author(s):  
Jessica Liptak ◽  
Gretchen Keppel-Aleks ◽  
Keith Lindsay

Abstract. The amplitude of the mean annual cycle of atmospheric CO2 is a diagnostic of seasonal surface–atmosphere carbon exchange. Atmospheric observations show that this quantity has increased over most of the Northern Hemisphere (NH) extratropics during the last 3 decades, likely from a combination of enhanced atmospheric CO2, climate change, and anthropogenic land use change. Accurate climate prediction requires accounting for long-term interactions between the environment and carbon cycling; thus, analysis of the evolution of the mean annual cycle in a fully prognostic Earth system model may provide insight into the multi-decadal influence of environmental change on the carbon cycle. We analyzed the evolution of the mean annual cycle in atmospheric CO2 simulated by the Community Earth System Model (CESM) from 1950 to 2300 under three scenarios designed to separate the effects of climate change, atmospheric CO2 fertilization, and land use change. The NH CO2 seasonal amplitude increase in the CESM mainly reflected enhanced primary productivity during the growing season due to climate change and the combined effects of CO2 fertilization and nitrogen deposition over the mid- and high latitudes. However, the simulations revealed shifts in key climate drivers of the atmospheric CO2 seasonality that were not apparent before 2100. CO2 fertilization and nitrogen deposition in boreal and temperate ecosystems were the largest contributors to mean annual cycle amplification over the midlatitudes for the duration of the simulation (1950–2300). Climate change from boreal ecosystems was the main driver of Arctic CO2 annual cycle amplification between 1950 and 2100, but CO2 fertilization had a stronger effect on the Arctic CO2 annual cycle amplitude during 2100–2300. Prior to 2100, the NH CO2 annual cycle amplitude increased in conjunction with an increase in the NH land carbon sink. However, these trends decoupled after 2100, underscoring that an increasing atmospheric CO2 annual cycle amplitude does not necessarily imply a strengthened terrestrial carbon sink.


Author(s):  
Liang-Jie Wang ◽  
Shuai Ma ◽  
Yong-Peng Qiao ◽  
Jin-Chi Zhang

Development of suitable ecological protection and restoration policies for sustainable management needs to assess the potential impacts of future land use and climate change on ecosystem services. The two ecological shelters and three belts (TSTB) are significant for improving ecosystem services and ensuring China’s and global ecological security. In this study, we simulated land use in 2050 and estimated the spatial distribution pattern of net primary productivity (NPP), water yield, and soil conservation from 2010 to 2050 under future climate change. The results showed that water yield, NPP, and soil conservation exhibited a spatial pattern of decreasing from southeast to northwest, while in terms of the temporal pattern, water yield and NPP increased, but soil conservation decreased. Water yield was mainly influenced by precipitation, NPP was affected by temperature and implementation of ecological restoration, and soil conservation was controlled by precipitation and slope. There was a strong spatial heterogeneity between trade-offs and synergies. In terms of the temporal, with the combination of climate change and ecological restoration, there was a synergistic relationship between water yield and NPP. However, the relationships between water yield and soil conservation, and between NPP and soil conservation were characterized by trade-offs. In the process of ecological construction, it is necessary to consider the differences between overall and local trade-offs and synergies, as well as formulate sustainable ecological management policies according to local conditions. Understanding the response of ecosystem services to future climate change and land use policies can help address the challenges posed by climate change and achieve sustainable management of natural resources.


Forests ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 176 ◽  
Author(s):  
Kevin Thellmann ◽  
Reza Golbon ◽  
Marc Cotter ◽  
Georg Cadisch ◽  
Folkard Asch

Land use and climate change exert pressure on ecosystems and threaten the sustainable supply of ecosystem services (ESS). In Southeast-Asia, the shift from swidden farming to permanent cash crop systems has led to a wide range of impacts on ESS. Our study area, the Nabanhe Reserve in Yunnan province (PR China), saw the loss of extensive forest areas and the expansion of rubber (Hevea brasiliensis Müll. Arg.) plantations. In this study, we model water yield and sediment export for a rubber-dominated watershed under multiple scenarios of land use and climate change in order to assess how both drivers influence the supply of these ESS. For this we use three stakeholder-validated land use scenarios, varying in their degree of rubber expansion and land management rules. As projected climate change varies remarkably between different climate models, we combined the land use scenarios with datasets of temperature and precipitation changes, derived from nine General Circulation Models (GCMs) of the Fifth Assessment Report of the IPCC (Intergovernmental Panel on Climate Change) in order to model water yield and sediment export with InVEST (Integrated Valuation of Ecosystem Services and Trade-offs). Simulation results show that the effect of land use and land management decisions on water yield in Nabanhe Reserve are relatively minor (4% difference in water yield between land use scenarios), when compared to the effects that future climate change will exert on water yield (up to 15% increase or 13% decrease in water yield compared to the baseline climate). Changes in sediment export were more sensitive to land use change (15% increase or 64% decrease) in comparison to the effects of climate change (up to 10% increase). We conclude that in the future, particularly dry years may have a more pronounced effect on the water balance as the higher potential evapotranspiration increases the probability for periods of water scarcity, especially in the dry season. The method we applied can easily be transferred to regions facing comparable land use situations, as InVEST and the IPCC data are freely available.


Author(s):  
Colin D. Campbell ◽  
Allan Lilly ◽  
Willie Towers ◽  
Stephen J. Chapman ◽  
Alan Werritty ◽  
...  

ABSTRACTLand use and the management of our natural resources such as soils and water offer great opportunities to sequester carbon and mitigate the effects of climate change. Actions on forestry, soil carbon and damaged peatlands each have the potential to reduce Scottish emissions in 2020 by hundreds of thousands of tonnes. Most actions to reduce emissions from land use have beneficial effects on other ecosystem services, so if we can cut emissions we can in many circumstances improve the environment. The cost of reducing emissions through land use change can be low in relation to other means of cutting emissions. The Scottish Land Use Strategy and the Ecosystem Approach it calls for, employing the concept of ecosystem services, offers a way of balancing environmental, social and economic demands on the land. Scotland's land, soils, forests and waters are all likely to be significantly altered by future climate change. Each of these components of the land-based environment offers opportunities for mitigation and adaptation to climate change. The emerging new imperatives for securing food, water and energy at a global level are equally important for Scotland, and interact with the need for environmental security and for dealing with climate change.


2021 ◽  
Vol 21 (3) ◽  
Author(s):  
Susanne Rolinski ◽  
Alexander V. Prishchepov ◽  
Georg Guggenberger ◽  
Norbert Bischoff ◽  
Irina Kurganova ◽  
...  

AbstractChanges in land use and climate are the main drivers of change in soil organic matter contents. We investigated the impact of the largest policy-induced land conversion to arable land, the Virgin Lands Campaign (VLC), from 1954 to 1963, of the massive cropland abandonment after 1990 and of climate change on soil organic carbon (SOC) stocks in steppes of Russia and Kazakhstan. We simulated carbon budgets from the pre-VLC period (1900) until 2100 using a dynamic vegetation model to assess the impacts of observed land-use change as well as future climate and land-use change scenarios. The simulations suggest for the entire VLC region (266 million hectares) that the historic cropland expansion resulted in emissions of 1.6⋅ 1015 g (= 1.6 Pg) carbon between 1950 and 1965 compared to 0.6 Pg in a scenario without the expansion. From 1990 to 2100, climate change alone is projected to cause emissions of about 1.8 (± 1.1) Pg carbon. Hypothetical recultivation of the cropland that has been abandoned after the fall of the Soviet Union until 2050 may cause emissions of 3.5 (± 0.9) Pg carbon until 2100, whereas the abandonment of all cropland until 2050 would lead to sequestration of 1.8 (± 1.2) Pg carbon. For the climate scenarios based on SRES (Special Report on Emission Scenarios) emission pathways, SOC declined only moderately for constant land use but substantially with further cropland expansion. The variation of SOC in response to the climate scenarios was smaller than that in response to the land-use scenarios. This suggests that the effects of land-use change on SOC dynamics may become as relevant as those of future climate change in the Eurasian steppes.


2018 ◽  
Vol 11 (11) ◽  
pp. 4537-4562 ◽  
Author(s):  
HyeJin Kim ◽  
Isabel M. D. Rosa ◽  
Rob Alkemade ◽  
Paul Leadley ◽  
George Hurtt ◽  
...  

Abstract. To support the assessments of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), the IPBES Expert Group on Scenarios and Models is carrying out an intercomparison of biodiversity and ecosystem services models using harmonized scenarios (BES-SIM). The goals of BES-SIM are (1) to project the global impacts of land-use and climate change on biodiversity and ecosystem services (i.e., nature's contributions to people) over the coming decades, compared to the 20th century, using a set of common metrics at multiple scales, and (2) to identify model uncertainties and research gaps through the comparisons of projected biodiversity and ecosystem services across models. BES-SIM uses three scenarios combining specific Shared Socio-economic Pathways (SSPs) and Representative Concentration Pathways (RCPs) – SSP1xRCP2.6, SSP3xRCP6.0, SSP5xRCP8.6 – to explore a wide range of land-use change and climate change futures. This paper describes the rationale for scenario selection, the process of harmonizing input data for land use, based on the second phase of the Land Use Harmonization Project (LUH2), and climate, the biodiversity and ecosystem services models used, the core simulations carried out, the harmonization of the model output metrics, and the treatment of uncertainty. The results of this collaborative modeling project will support the ongoing global assessment of IPBES, strengthen ties between IPBES and the Intergovernmental Panel on Climate Change (IPCC) scenarios and modeling processes, advise the Convention on Biological Diversity (CBD) on its development of a post-2020 strategic plans and conservation goals, and inform the development of a new generation of nature-centred scenarios.


2021 ◽  
Vol 18 (18) ◽  
pp. 5053-5083
Author(s):  
Jessica L. McCarty ◽  
Juha Aalto ◽  
Ville-Veikko Paunu ◽  
Steve R. Arnold ◽  
Sabine Eckhardt ◽  
...  

Abstract. In recent years, the pan-Arctic region has experienced increasingly extreme fire seasons. Fires in the northern high latitudes are driven by current and future climate change, lightning, fuel conditions, and human activity. In this context, conceptualizing and parameterizing current and future Arctic fire regimes will be important for fire and land management as well as understanding current and predicting future fire emissions. The objectives of this review were driven by policy questions identified by the Arctic Monitoring and Assessment Programme (AMAP) Working Group and posed to its Expert Group on Short-Lived Climate Forcers. This review synthesizes current understanding of the changing Arctic and boreal fire regimes, particularly as fire activity and its response to future climate change in the pan-Arctic have consequences for Arctic Council states aiming to mitigate and adapt to climate change in the north. The conclusions from our synthesis are the following. (1) Current and future Arctic fires, and the adjacent boreal region, are driven by natural (i.e. lightning) and human-caused ignition sources, including fires caused by timber and energy extraction, prescribed burning for landscape management, and tourism activities. Little is published in the scientific literature about cultural burning by Indigenous populations across the pan-Arctic, and questions remain on the source of ignitions above 70∘ N in Arctic Russia. (2) Climate change is expected to make Arctic fires more likely by increasing the likelihood of extreme fire weather, increased lightning activity, and drier vegetative and ground fuel conditions. (3) To some extent, shifting agricultural land use and forest transitions from forest–steppe to steppe, tundra to taiga, and coniferous to deciduous in a warmer climate may increase and decrease open biomass burning, depending on land use in addition to climate-driven biome shifts. However, at the country and landscape scales, these relationships are not well established. (4) Current black carbon and PM2.5 emissions from wildfires above 50 and 65∘ N are larger than emissions from the anthropogenic sectors of residential combustion, transportation, and flaring. Wildfire emissions have increased from 2010 to 2020, particularly above 60∘ N, with 56 % of black carbon emissions above 65∘ N in 2020 attributed to open biomass burning – indicating how extreme the 2020 wildfire season was and how severe future Arctic wildfire seasons can potentially be. (5) What works in the boreal zones to prevent and fight wildfires may not work in the Arctic. Fire management will need to adapt to a changing climate, economic development, the Indigenous and local communities, and fragile northern ecosystems, including permafrost and peatlands. (6) Factors contributing to the uncertainty of predicting and quantifying future Arctic fire regimes include underestimation of Arctic fires by satellite systems, lack of agreement between Earth observations and official statistics, and still needed refinements of location, conditions, and previous fire return intervals on peat and permafrost landscapes. This review highlights that much research is needed in order to understand the local and regional impacts of the changing Arctic fire regime on emissions and the global climate, ecosystems, and pan-Arctic communities.


2016 ◽  
Author(s):  
Fang Zhao ◽  
Ning Zeng ◽  
Ito Akihiko ◽  
Ghassam Asrar ◽  
Pierre Friedlingstein ◽  
...  

Abstract. We examined the net terrestrial carbon flux to the atmosphere (FTA) simulated by nine models from the TRENDY dynamic global vegetation model project during 1961–2012 for its seasonal cycle and amplitude trend. While some models exhibit similar phase and amplitude compared to atmospheric inversions, with spring drawdown and autumn rebound, others tend to rebound early in summer. The model ensemble mean underestimates the magnitude of the seasonal cycle by 40 % compared to atmospheric inversions. Global FTA amplitude increase (19 ± 8 %) and its decadal variability from the model ensemble are generally consistent with constraints from surface atmosphere observations. However, models disagree on attribution of this long-term amplitude increase, with factorial experiments attributing 83 ± 56 %, −3 ± 74 % and 20 ± 30 % to rising CO2, climate change and land use/cover change, respectively. Seven out of the nine models suggest that CO2 fertilization is a stronger control — with the notable exception of VEGAS, which attributes approximately equally to the three factors. Generally, all models display an enhanced seasonality over the boreal region in response to high-latitude warming, but a negative climate contribution from part of the Northern Hemisphere temperate region, and the net result is a divergence over climate change effect. Six of the nine models show land use/cover change amplifies the seasonal cycle of global FTA: some are due to forest regrowth while others are caused by crop expansion or agricultural intensification, as revealed by their divergent spatial patterns. We also discovered a moderate cross-model correlation between FTA amplitude increase and increase in land carbon sink (R2 = 0.61). Our results suggest that models can show similar results in some benchmarks with different underlying mechanisms, therefore the spatial traits of CO2 fertilization, climate change, and land use/cover changes are crucial in determining the right mechanisms in seasonal carbon cycle change as well as mean sink change.


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