Biodiversity and ecosystem services in the Earth system
Final Report Abstract
The supply of ecosystem services such as food production, species richness or climate stabilization is necessary for human survival and welfare. However, many ecosystem services have been strongly utilized throughout recent decades because humans exploit natural resources and thereby threaten the provision of ecosystem services. In addition to human land use, climate change and elevated atmospheric CO2 concentrations influence ecosystems. An assessment of how vegetation, climate change and human land use interact requires the capacity to simulate vegetation dynamics, functional diversity, carbon and water fluxes and their responses to land use. Ecologists have large expertise in modeling ecosystem dynamics. Dynamic global vegetation models (DGVMs) are a well-established class of models used to simulate past, present and future vegetation dynamics. DGVMs simulate ecological processes, carbon and water cycles, and biome distribution patterns based on environmental conditions. Yet, in many DGVMs vegetation is represented by static plant functional types that aggregate similar plant species. The huge variation within and between species that we observe in nature is often ignored. The aim of the proposed project was to develop a novel DGVM that simulates vegetation dynamics, functional diversity and ecosystem services as well as the impacts of climate change and land use. We therefore improved the representation of vegetation in the trait-based vegetation model aDGVM2. The model allows each individual plant to adopt trait values from a pre-defined trait space. Selection, trait inheritance, mutation and cross-over are used to imitate plant community assembly. That is, individuals with trait values that allow the plant to grow and reproduce in a given environment can pass their traits to the next generation while other individuals are out-competed. We developed novel sub-models for ecophysiology, plant hydraulics, competition and demography, extended the spatial domain of the model from the original focus on Africa to the pantropics, and coupled it with economic models for management policy assessments. We applied the model in different case studies and regions. (1) We studied diversity in Amazonian forests and Cerrados and we found that plant diversity can buffer effects of droughts and climate change on ecosystems. Drought impacts were lower in more diverse plant communities than in monocultures. The aDGVM2 simulated realistic biogeographic patterns of life history strategies such as deciduous or evergreen vegetation. (2) We focused on vegetation patterns in tropical Asia. These areas host several global biodiversity hotspots but detailed DGVM studies are lacking. We proposed a research agenda for DGVM studies in these regions and then conducted simulations for multiple climate change scenarios and CO2 scenarios to quantify changes in biome patterns, phenology and diversity. We found that many regions are likely to experience increases in biomass and transitions from open ecosystems to forests due to CO2 fertilization. (3) For selected sites in the study region, we simulated the impacts of drought and showed that aDGVM2 reproduces realistic ranges of drought-induced tree mortality. Drought impacts and recovery rates are strongly related to trait diversity in the pre-drought community, traits of individual plants and drought length. (4) We simulated vegetation in Africa under equilibrium climate conditions and under transient conditions. We showed that equilibrium states deviate from transient states and that future vegetation states have no analogue equilibrium vegetation state. These results highlight that management or conservation practices need to take into account that vegetation is prone to further changes even if the rate of climate change should be slowed down or land use practice should be changed. (5) We evaluated the economic value two important ecosystem services, livestock production and fuelwood, in a South African savanna rangeland. We therefore coupled aDGVM with an economic model and optimization routines and found that optimal and sustainable land policies deviate substantially from currently applied land use intensities. The aDGVM2 deals with functional diversity and competition fundamentally differently from other DGVMs. Our results yield novel insights as to how vegetation may respond to climate change or land use at the trait, plant, community and biome level. The aDGVM2 modeling approach can foster collaborations between functional plant biology, vegetation modeling, ecosystem service science, economy, and conservation managers.
Publications
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(2017) Climate-biomes, pedo-biomes or pyro-biomes: which world view explains the tropical forest – savanna boundary in South America? Journal of Biogeography, 44, 2319–2330
Langan L, Higgins SI, Scheiter S
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(2019) Biome diversity in South Asia - how can we improve vegetation models to understand global change impact at regional level? Science of the Total Environment, 671, 1001–1016
Kumar D, Scheiter S
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(2020) African biomes are most sensitive to changes in CO2 under recent and near-future CO2 conditions. Biogeosciences, 17, 1147–1167
Scheiter S, Moncrieff GR, Pfeiffer M, Higgins SI
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(2020) Climate change promotes transitions to tall evergreen vegetation in tropical Asia. Global Change Biology, 26, 5106–5124
Scheiter S, Kumar D, Corlett RT, Gaillard C, Langan L, Lapuz RS, Martens C, Pfeiffer M, Tomlinson KW
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(2020) Climate change will cause non-analogue vegetation states in Africa and commit vegetation to long-term change. Biogeosciences, 17, 5829–5847
Pfeiffer M, Kumar D, Martens C, Scheiter S
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(2020) Misinterpretation of Asian savannas as degraded forest can mislead management and conservation policy under climate change. Biological Conservation, 241, 108293
Kumar D, Pfeiffer M, Gaillard C, Langan L, Martens C, Scheiter S
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(2020) Wie beeinflusst Klimawandel die Vegetation in den Tropen Asiens? In: Tockner K (Hrsg.). Jahresbericht der Senckenberg Gesellschaft für Naturforschung, 18–21
Scheiter S, Kumar D
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(2021) Climate change and elevated CO2 favor forest over savanna under different future scenarios in South Asia. Biogeoscience, 18, 2957–2979
Kumar D, Pfeiffer M, Gaillard C, Langan L, Scheiter S
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(2021) Savannen der Erde und ihre Gefährdung. In: Lozan JL, Breckle S-W, Graßl H, Kasang D (Hrsg.). Warnsignal Klima: Boden & Landnutzung. 87–92
Scheiter S, Pfeiffer M
