Cold Rocky Landforms: rock aggregates that prove essential for the protection of mountain biodiversity
Due to climate change, cold aquatic environments in high mountains, such as glacier springs, are rapidly shrinking. However, certain landforms called cold rocky landforms (CRLs), can help protect these environments and their biodiversity.
CRLs comprise a wide variety of landforms that differ in origin and appearance. Their common characteristic is a surface composed of coarse rock fragments that favors unique air ventilation and the maintenance of cold conditions in their interior, even in unfavorable climatic settings. Furthermore, many CRLs act as aquifers, thus feeding springs and lakes. Surprisingly, the knowledge of the hydrology and ecology of these waters is still very limited.
The new study, in which Eco Research collaborated with an international team of researchers, examined the temperature of springs fed by CRLs in a variety of mountain environments in Europe, North America, and South America. The aim of the study was to understand whether these springs are thermally similar or different from those more commonly found in mountains. The results show that:
- Springs originating from CRLs are often as cold as those from glaciers (<2°C) and are much colder (up to 9°C) than nearby springs not influenced by CRLs.
- Cold springs (<2°C) are rarer in warm and dry mountains such as those with a Mediterranean climate, where, however, the difference between CRLs and reference springs is greater.
- The CRLs most likely sourcing cold springs are those composed of coarse rock fragments and with less soil and vegetation cover. These CRLs more likely host ice within them.
Springs originating from CRLs could be important for the conservation of mountain biodiversity because they may provide a climate refuge for many cold-adapted organisms, thus protecting them from the effects of global warming. Further studies will be needed to understand the biodiversity of these environments and identify CRLs that require priority protection from human activities.
A B S T R A C T
Climate change is reducing the extent of cold aquatic habitats and their unique biodiversity in mountain areas. However, a variety of cold rocky landforms (CRLs) are thermally buffered and feed cold springs (<2 °C) that may represent climate refugia for cold-adapted organisms. These landforms, hitherto overlooked by freshwater research, include rock glaciers, debris-covered glaciers, talus slopes, protalus ramparts, and young moraines. Here, we investigated the warm-season water temperature of 228 springs from clean (ice) glaciers, CRLs, and reference slopes (not sourced by any of these features) in 13 mountain ranges of Europe, South America, and North America. Only springs from glaciers (90%) and CRLs (45%) had average stream temperatures below the thermal optimum for coldwater organisms of 2 °C. Springs fed by CRLs were 3 °C–5 °C (up to 9 °C) colder than those from nearby reference slopes. In general, cold springs were rarer in Mediterranean/semi-arid climates than in temperate and sub-polar climates. Landforms comprising barren and coarse rocky surfaces or ice/rock mix, having a simple or absent soil/vegetation structure, and higher likelihood of permafrost more often supported cold springs. When water temperatures were compared to air temperature, most CRL springs were thermally buffered against warm periods, cumulative heat, and daily temperature fluctuations. With cold conditions maintained in a variety of climates and mountain landscapes, CRL springs in mountains likely have high conservation value. We call for integrated ecological and hydrological research for these ecosystems, aimed at understanding their potential as climate refugia.