Klimatets effekter på biologisk mångfald i Sverige: en kunskapssammanställning med sårbarhetsanalys och förslag på indikatorer

This report presents a current picture of the overall state of knowledge about how the effects of climate change affect the Swedish natural environment. The report also proposes indicators to be able to follow developments over time through environmental monitoring. Our planet has already become more than one degree warmer compared to pre-industrial times, and measurement series for the impact of climate change in Sweden point to clear changes in both temperature and precipitation patterns. The report shows that several of the effects of climate change; changed precipitation patterns, higher temperatures, reduced snow cover, longer growing seasons, groundwater levels, rising sea levels and more extreme weather will have an impact on all of Sweden’s habitat types and their species. For Scandinavian conditions, it is likely that climate change will cause a northward shift of the different growing zones and species abundance as the climate warms. Such a shift entails new and changed ranges, competitive conditions and interactions between species, where some species are expected to benefit while others are displaced. In the Swedish mountain range, the temperature increase is almost twice as fast as the global average, which puts great pressure on northern and Arctic species that are linked to this habitat type. There are many specialized species here with limited opportunities for northward migration, whose habitats are reduced. Several climate-related effects such as decreasing and changing snow conditions, zero crossings, increased overgrowth rate of bare mountain environments, altered biotic interactions, distribution of southern and invasive species and higher temperatures affect the species in the mountain environment. Some examples that are pointed out in the report are snowgrass, wolverine, reindeer, mountain bumblebee and small rodents. A warmer and more precipitous climate risks leading to a number of different effects of significance for lakes and watercourses. Higher water temperatures, altered flows, reduced ice cover, oxygen deficiency, brownification, drying out and changes in land use affect both individual species and the entire food web. Coldwater species such as char, whitefish and large mussels are particularly at risk of being negatively affected. However, some freshwater-related species, such as dragonflies, are expected to benefit from a warmer climate. A changing climate also entails changes in water temperatures, salinity, brownification, pH values, oxygenation, ice formation patterns, wind and wave patterns and currents, which are expected to have significant consequences for the ocean’s ecosystems. Analyses show that the impact of climate change is in the order of magnitude of all the cumulative environmental impacts that exist from other pressures at present. Some species that are affected according to the report are, bladderwrack, eelgrass and ringed seal. Species living in marine coastal environments are also affected, where, for example, the sand lizard and the field pipit are threatened by reduced habitats in the event of sea level rise or the spread of new invasive species such as the cotula. 8 NATURVÅRDSVERKET RAPPORT 7179 Klimatets effekter på biologisk mångfald i Sverige Wetlands are important ecosystems for both biodiversity and the climate challenges and are particularly sensitive to high temperatures and droughts. Different types of wetlands are affected differently by climate change, but a general pattern of increased tree growth on the marshes is visible in Sweden. Particularly sensitive are the so-called palsa mires, which are collapsing as a result of thawing permafrost. The Swedish forest is expected to benefit from a warmer climate with a longer growing season. For example, in many places, the tree line for mountain birch, spruce and pine has moved up to 200 m over the past century, which is in line with the measured temperature change. At the same time, climate-related disturbances in the forest such as frost damage, drought, forest fires, storm damage, tree diseases and insect attacks are increasing. This affects the conditions for both species composition and distribution. The species that live in the forest are affected by, among other things, changes and decreases in snow cover, the shift in the tree line and changes in the composition of wood species. The agricultural landscape and the species associated with these habitats are affected by, among other things, temperature increases and changed precipitation patterns that lead to longer growing seasons and drier conditions in parts of southern Sweden. Heat-favoured species are expected to benefit at the expense of northern species, and changes in the flowering season can affect the availability of nectar and pollen for many insects. Many of the bird species that winter in more southern latitudes also arrive earlier in the spring. Land use plays a major role in biodiversity and the well-being and resilience of ecosystems. Land use itself is expected to be affected by climate change, where, for example, changes in farming practices in response to change, in the short term, which may have a greater impact on biodiversity than the effects of climate change. A changing climate can thus be expected to lead to significant changes for Sweden’s biodiversity, both in terms of individual species and habitat types, as well as the constituent ecological functions of the ecosystems. Developing indicators to be able to identify and monitor the impact of climate change on species and natural environments will thus be a central part of the work of being able to prioritise and point out appropriate nature conservation efforts. This report presents a first draft with proposals for indicators for both terrestrial and aquatic ecosystems in order to be able to follow the changes in the natural environment. The indicators are mainly based on data from existing measurement series and citizen science. For terrestrial environments, the report suggests suitable indicators; phenology, species distribution, temperature index for plants, area of open peatland, occurrence of invasive species, and area of glacier and other habitats. For aquatic environments, about 30 proposals are submitted for both direct indicators with data from test fishing, national and regional environmental monitoring as well as indirect indicators such as changes in pH weather, salinity, watercolor or water chemistry changes. The greater number of aquatic indicators should be seen as a toolbox from which appropriate indicators can be selected.