Integrated assessment to aid mitigation of negative impacts by THREE global change Drivers on alpine biodiversity and ecosystem function

Fjellområder gir viktige leveområder for mange plante- og dyrearter, og de bidrar også med viktige økosystemfunksjoner og -tjenester som karbonlagring, områder for utmarksbeite og regulering av flom og jordskred. Samtidig er fjelløkosystemene spesielt utsatt for globale forandringer.

Varmere klima, nitrogenforurensning og beite er viktige menneskelige påvirkninger på naturen og økosystemtjenestene. Både varmere klima og nitrogen øker næringstilgang og dermed produktiviteten i økosystemene, noe som ofte fører til lavere biologisk mangfold. I tillegg kan disse påvirkningene også endre karbonlagringen i jorda på grunn av høyere nedbryting av organisk materiale. Beite øker også næringstilgang og produktivitet i økosystemet, men samtidig fjerner beitedyra biomasse. Beiteintensiteten er avgjørende for om effekten av beite øker eller minker det biologiske mangfoldet. Effekten fra hver enkelt av disse tre påvirkningsfaktorene på biologisk mangfold er godt undersøkt, men i et naturlig system vil alle effektene virke sammen. Og nettopp disse samvirkningene kan ha komplekse konsekvenser for karbonlagring og biologisk mangfold.

I THREE-D undersøker vi disse komplekse samvirkningene ved hjelp av et felteksperiment. Vi utsetter fjellvegetasjon for varmere klima, nitrogendeposisjon og forskjellig beitetrykk, og undersøker hvordan dette påvirker biologisk mangfold og karbonlagring. Videre vil vi undersøke i hvilken grad forskjellig beitetrykk kan redusere negative effekter på økosystemet.

Resultatene av eksperimentet vil også brukes i modellsimuleringer for å kunne si noe om konsekvensene av global forandring for biologisk mangfold og karbonlagring på større skala, og under forskjellige fremtidige klimascenarier. THREE-D vil dermed bidra til økt kunnskap om og tilbakekoblinger mellom terrestriske økosystemer og klimasystemet.

Three of the most critical global change drivers are warming, nitrogen deposition, and grazing. All of these can have complex effects on biodiversity and ecosystem function, and, especially for biodiversity, effects can often be negative. For plant communities, these impacts operate through many of the same ecological pathways, involving changes in plant productivity and biomass as well as carbon cycling processes. In this proposal we argue that by combining these pathways into a single predictive framework we can both assess their complex interactions and, importantly, generate approaches to mitigate their combined effects on biodiversity and ecosystem function. In particular, we take advantage of two key aspects of grazing: (i) its impacts depend in a nonlinear and even non-monotonic way on plant productivity, and (ii) it is being amenable to manipulation at a local scale. This enables us to explore the circumstances under which grazing is itself a major ecological stressor vs. acting as an effective tool for reducing the ecological strains caused by climate warming and/or nitrogen deposition. To assess effects of three global change drivers and their impacts on ecosystem using a single framework, represents a significant advancement beyond the state-of-the-art. THREE-D is also innovative in that it goes beyond studying impacts of global change by exploring the potential of grazing as a management tool.

We study alpine ecosystems, which are particularly vulnerable to global change because climate is warming more than the global average and because alpine species have ‘nowhere to go’ under climate change. The questions addressed in this proposal are relevant to the UN 2030 Agenda for sustainable development (un.org/sustainabledevelopment/) goal 15 ‘Life on land’, which specifically aims “... to ensure the conservation of mountain ecosystems, including their biodiversity, in order to enhance their capacity to provide benefits that are essential for sustainable development.” Further, this project is closely aligned with the Research Council’s strategy “Styrke forskning som bidrar til bærekraftige løsninger i samfunn og næringsliv” and their KLIMAFORSK programme “to generate knowledge about natural and anthropogenic climate change, the impacts of climate change on nature and society, …”.

The THREE-D team builds on a successful collaboration between a Norwegian and a Chinese research institution and will develop and expand their national and international network with new partners from Norway, China, Switzerland, and the USA. THREE-D will support an early-career researcher in building an independent scientific profile, while the feasibility of the project will be enhanced by guidance from a Senior PI on leadership and coordination throughout the project. The THREE-D team has access to special infrastructure and relevant data and has the expertise for synthesis and comparative research as well as being uniquely positioned to deliver any important research outcomes and mitigation strategies.

We will establish two parallel experiments (Norway and China) in alpine ecosystems (WP1; PI), where we expose an alpine plant community to warmer climate (transplant to lower elevation), increased nitrogen deposition (N addition), and different grazing levels in a fully factorial design to assess and disentangle their combined effect on biodiversity (WP2; PI) and ecosystem function (WP3; Lee). These experiments are designed to further allow us to assess the potential of managing grazing so as to mitigate the effects of warming and/or nitrogen on alpine biodiversity (WP2; PI) and ecosystem function (WP3; Lee). To describe these ecological pathways between the three drivers and biodiversity and ecosystem function in a framework, we need accurate estimates of plant productivity, biomass, decomposition, and soil carbon, which will be undertaken in WP2 and WP3. Finally, we will develop a management decision-support tool, in collaboration with farmers and local conservation managers, to estimate the impact of the current level of grazing and to explore the potential of adaptation of the grazing regime to meet new pressures and/or optimise ecosystem service delivery in an alpine ecosystem (WP4, PI, Ryum). The tool will be developed by collecting data from a meta-analysis on existing global grazing manipulation experiments. We will test the tool using the data generated in this project.