CLAIMES

Climate response of alpine lakes: resistance variability and management consequences for ecosystem services

CLAIMES

Due to their pristine nature remote alpine lakes are considered most valuable. Up to date the ecosystem services (ES) of alpine lakes are poorly characterized. The central aim of this 3 years project is to find out how ongoing climate change affects the function of alpine lakes and in consequence the provision of ES requiring new management advices taking climate change into account. This topic is of relevance with regard to the general understanding that in consequence to global warming those alpine lakes might experience more intense use within the near + distant future. The study design takes advantage from long-term limnological monitoring of alpine lakes located in the Northern Alps as well as in the Southern Alps.
In a first step the variability of the response of these alpine lakes to global warming within the last two decades will be explored on a quantitative scale. Lake surface temperature (LST) reconstructions covering the previous decades will be validated by in situ temperature records from two decades earlier and also recorded during this project. Plankton and fish community will be analysed using modern metabarcoding techniques based on deep-amplicon sequencing. The observation period further will include data on limnological indicator organisms from sediment cores such as diatoms, chrysophytes and chironomids which have been analysed two decades ago and will now be reanalyzed for the same alpine lakes showing high variability in summer epilimnion temperature.
In a second step the ES will be quantitatively assessed for lake-types defined in relation to the UN sustainability developmental goals, such as accessibility, intensity of use or sensitivity to climate change. Provisioning and regulating ES (water provision/regulation) will be quantified using census data, data from limnological measurements as well as complex modelling approaches, whereas cultural ES (i.e. aesthetic value) will be based on crowd-sourced information such as geotagged photographs suitable to assess human preferences or by specific surveys based on questionnaires.  Socio-economic data (e.g. livestock feeding, fishing, tourism) will be collected. Validated LST models will allow for assessment of alpine lakes’ resistance towards disturbances which will affect the ability to maintain ES under potential impacts of climate change such as the IPCC “business as usual” scenario and the UN climate conference COP21 goal. In a third step the ES provided by those lakes will be evaluated using multi criteria decision analysis (MCDA) comparing representative lakes of defined lake-types in both model regions. This will include (i) defining the most important ES through an experts' round table, (ii) a pair-wise questionnaire for ecosystem services weighing to be compiled by local stakeholders from various interest groups, (iii) Attribution of ES indicators and (iv) Performance of MCDA. The ES management under a scenario of climate change as described above will be addressed through comparative ES evaluation for the near and more distant future. Finally policy recommendations to facilitate future ES management in order to guarantee sustainable ES provision will be elaborated and presented.

It is generally accepted that climate change threatens the integrity of alpine lakes more strongly and faster than comparable ecosystems in lowland regions. This is not only due to a generally more pronounced temperature rise in the alpine region but also due to the high vulnerability of alpine ecosystems. In addition, anthropogenic influences such as agriculture or touristic and recreational use increasingly threaten the same ecosystems, which is of concern as soon as goods and services provided by lakes get competitive.

For alpine lakes, it has been shown that lakes respond to climate change rather individually, which, for example, is caused by local habitat-specific influences. From a large physico-chemical alpine lake data set from the Niedere Tauern (NT) region in the Austrian Alps (n = 20) but also from long-term monitored lakes in the North of Italy (n=10, LTER Italia, sites IT09 and IT25) a wide scatter in the decrease of summer epilimnion water temperature as a function of altitude has been observed (Kamenik, Schmidt et al. 2001; Thompson, Kamenik et al. 2005). It has been shown that altitude, topographic shading, and bathymetry, all influence lake surface water temperature and ice cover duration in response to air temperature (Novikmec, Svitok et al. 2013). For example, topographic shading led to the decoupling of an alpine lake Haegelseewli (2339 m a.s.l.) from climate forcing due to ice cover formation during the larger part of the year, thus minimising the direct temperature effects during the short open water season (Lotter, Appleby et al. 2002). Furthermore, it is well known that e.g. lake depth and residence time, control the climatic response and cause dissimilar lake responses (Blenckner 2005). This variable response to a common driver leads to either undercooled or relatively warm lakes located at the same altitude, for example a range in mean summer epilimnion water temperature from 7.5-11.3°C at an altitude from 1929 –1970 m a.s.l..

Local variability also has the potential to interact with climate change effects that influence biodiversity and ecosystem function. It has been described how climate related impacts can change phytoplankton biodiversity and ecosystem function within the relatively short-term (10 years), e.g. through changes in ice cover duration reducing phytoplankton biomass and productivity and drainage of DOC favouring mixotrophic algae (Parker, Vinebrooke et al. 2008). There is evidence that species number and species richness have functional consequences, for example, resource use efficiency has been shown to be correlated to species diversity in phytoplankton, using a large data set of samples from Scandinavia and the Baltic Sea (Ptacnik, Solimini et al. 2008). Vice versa a high biodiversity can influence the resistance of lakes against invasive species (e.g. Schallenberg et al. 2013). There is some evidence that a high biodiversity can also lead to higher ecosystem resistance against anthropogenic influences, such as eutrophication (Cardinale 2011), (Thompson and Shurin 2012). Consequently, lakes with reduced plankton diversity might even experience an exaggeration of consequences (algal bloom formation) from ES provision side effects.

Aquatic ecosystems have long been known for showing non-linear ecosystem behaviour in relatively short periods, (Carpenter and Brock 2011). For example, undercooled lakes which are nutrient-rich due to human activities in the catchment area (L. Moaralmsee) will likely have algal blooms as soon as the ice-free vegetation period increases in consequence to climate change (Wecksröm et al. 2016). Such regime shifts would have significant consequences on the ecosystem level, e.g. high algal biomass production during summer and oxygen consumption during the ice cover period resulting in a cascade of changes in the whole ecosystem. Modelling experiments have revealed that such regime shifts can be foreseen already through long-term monitoring by statistical anomalies, for example, through the increased variance in residues from dependent variables in linear regression models (Seekell, Carpenter et al. 2011).

In summary, since the variables affecting each lake’s resistance to changing conditions are different, it is difficult to draw general conclusions on how alpine lakes are affected by global temperature warming. Consequently, when determining the response of alpine lakes, it is necessary to apply strategies which take their individual character into account. Exchange processes through the air-water interface allow for depicting lake surface temperatures (LSTs) via models containing atmospheric covariates (e.g. Matulla et al. 2018). In a second step distinct types of lakes could be classified according to climate change response, intensity of use, remoteness and potentially other factors such as hydrological forces allowing to forecast lakes response to climate change and human affairs in general.

The forecast of alpine lakes response is considered important as due to their pristine nature, alpine lakes are considered of highest value. However, up to date, ecosystem services (ES) of alpine lakes are poorly characterised. The ES concept has become popular since the United Nations' Millennium Ecosystem Assessment 2005 (MEA 2005). ES are defined as the benefits to humanity deriving from the functioning of ecosystems (MEA 2005). These benefits can be divided into market and non-market ecosystem goods or services and classified in multiple ways (Costanza 2001), e.g. provisioning services, regulating services, habitat or supporting services and cultural services (The Economics of Ecosystems and Biodiversity, further referred to as (TEEB 2010). Common frameworks such as TEEB facilitate scientific work when dealing with the complexity of landscapes (de Grootet al. 2010), but so far it is little known and applied by regional, administrative authorities. The ES perspective is conceptually because ES are co-produced by the ecosystems and human agency by means of labour, technology or financial resources (Palomo et al. 2016). Thus, it views ecosystems as socio-ecological entities and links ecosystems and their biodiversity with socio-economic systems (Boulton et al. 2016). Numerous ES have been related to lakes, for example water provision and regulation, water quality improvement, sediment retention and filtration, carbon and nutrient sequestration, wildlife habitat (e.g., waterfowl, breeding bird species) as well as aesthetic and recreational services (Sierszen et al. 2012, Loeffler et al. 2018). Nevertheless, studies addressing ES of alpine lakes in a systematic manner and in quantitative terms are still rare. In general, ES from lakes in Europe seem to be less considered when compared with other societies such as from North America or New Zealand. In particular, cultural (e.g. aesthetic, recreational, spiritual) ES have been rarely considered, although these services are important in combination with touristic use. This lack of knowledge is of relevance, as it is predicted that depending on global warming in the lowlands (e.g. the increasing frequency of heat waves during summer) the importance of ES of alpine lakes (e.g. its use for recreation) will increase.

Increasing summer tourism (Kromp-Kolb and Schwarzl 2007) in the Alps due to warmer and drier summers, may increase the intensity of use of lakes, especially of those located on higher altitudes, and may cause local problems (EEA 2009). In general, conflicts between different types of water usage can be expected to increase. For example, for alpine lakes which are easy accessible (e.g. Unterer Giglachsee, Table 1) such conflict may be related to enhanced Arctic char introduction due to prolonged summer activities and economic profits from fisheries (Zick, Gassner et al. 2007). It is well known that alpine lakes are very sensitive to allochthonous predator invasions potentially affecting the entire ecosystem through trophic cascade effects (Magnea, Sciascia et al. 2013). It is expected that lakes that already show relatively high traffic due to road accessibility will be at higher risk of suffering from intensive use (e.g. Lago di Braies, Lago di Anterselva). In this context, global warming will rather indirectly than directly increase the environmental pressure on the ecosystem integrity.

A higher intensity of use of alpine lakes is frequently coupled to eutrophication influence, e.g. probably through fish feeding, the nitrate concentrations have been increased in Lake Moaralmsee (1825 m a.s.l.), (Weckström et al. 2016). During recent years of observation (2009-2012), Lake Moaralmsee had an immigration of the diatom Asterionella formosa (Catalan, Pla-Rabes et al. 2013), and compared with other lakes a significantly reduced species diversity (both eukaryotic algae and bacteria), (Kurmayer and co-authors 2013). In summary conflicts may arise in the future from different interests through tourism favouring clear lakes, fisheries favouring higher production through fertilization and livestock feeding favouring water withdrawal during droughts.

When dealing with competing goods and services and when addressing conflicts arising from competing uses, the multi-criteria decision analysis has been shown to be an adequate tool, particularly due to its capacity to account for trade-offs (Langemeyer et al. 2016). In order to assess ES importance and consequently compare ES provision among alternatives, the multi-criteria decision analysis (MCDA) has been promoted (Langemeyer et al. 2016, Saarikoski et al. 2016) bridging from environmental sciences to economics. MCDA comprises a set of flexible methods which result in a transparent framework for integrated valuation of ES, allowing also the involvement of experts and stakeholders (Fontana et al. 2013, Langemeyer et al. 2016). Since, to the authors´ best knowledge, ES from alpine lakes so far have not been collected and evaluated in a systematic manner, this study provides novel and unique outcomes and goes even further modelling future ES provision. Doing so, we aim at identifying changes or losses in ES provision and elaborating policy advices in order to facilitate sustainable interventions.


The major aim of this inter- and transdisciplinary project is to compile limnological information on alpine lakes and to quantify and evaluate ES provision, which has not been studied in a systematic manner before. It is fundamental, to understand how climatic change affects the function of alpine lakes to characterize the variability of the response of alpine lakes on a quantitative scale as well as to explore the cumulative effect on ES under two predicted scenarios of climate change. This is necessary to characterize potential losses of ES presumably caused by ongoing alpine lake ecosystem deterioration. We want to answer the question which lake type is subjected to major changes in ES provision or even endangered to loose ES with ongoing climate change. The comparison of ES provided by alpine lakes differing in their response to climate warming will increase our capacity to predict future ES provision. We use MCDA to bridge the integrated ES approach to the policy and governmental level by raising awareness on potential arising conflicts due to changes in ES provision and plan to elaborate policy advices for an adaptive future ES governance.


Partner
Zentralanstalt für Meteorology und Geodynamik
University of Innsbruck, Faculty of Biology, Institute of Ecology
Universität für Bodenkultur Wien

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Manuel Ebner

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Biodiversity Monitoring South Tyrol

Biodiversity Monitoring South Tyrol

Duration: December 2018 - July 2021Funding:
Internal funding EURAC (Project)

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