This work is partially based on certain results acquired by the author’s contribution as expert within the project: “Consolidarea capacității instituționale pentru îmbunătățirea politicilor din domeniul schimbărilor climatice și adaptarea la efectele schimbărilor climatice” (“Strenghtening the institutional capacity for the improvement of the climate change policies and for the adaptation to the effects of climate change”) - SIPOCA Code/MySmis: 610/127579.
Special thanks go to the anonymous reviewers for the critical revision and the fair comments that improved the scientific quality of the manuscript.
1In Europe, the mountain regions are the most vulnerable to global warming (Thuiller et al., 2005) since these environments could be compared to “vertical islands” (Anderson, 2007) where the upward migration is the only way of species adaptation to climatic changes. In the Romanian Carpathians, a considerable fragmentation of the landscape at timberline and of the alpine belt (Czajka et al., 2015) increases fragility related to habitat insularity (Hurdu et al., 2012). Moreover, alpine zone habitats should be among the most affected by climate changes (Inouye, 2019), changes that disturb especially the thermal and hydroclimatic regimes, with effects on the vegetation cycle, its structure and distribution. One of the local effects of global warming is the gradual replacement of original species by those better adapted to the new climatic conditions. Among other effects, there are shorter snow-covered periods and earlier defrosting. A significant decrease of the annual number of days with snow cover was found for the 1961–2010 period at several weather stations from the Carpathian area in Romania (Bojariu et al., 2015). Over the same period of time, a significant increase of the annual number of days with precipitation over 20 mm was recorded in extensive areas of the Eastern and Western Carpathians.
2Plant communities from the alpine belt should be adapted to a very short growing season corresponding to the snow-free period of the year and require enough available water to enter the growth cycle (Beniston, 2003). As studied elsewhere on the European continent, the extension of the activity season and higher temperatures result in the upward migration of treeline (Gitay et al., 2002; Theurillat and Guisan, 2001) and in the gradual shrinking of the alpine belt, whose specific habitats are restrained to narrower areas and could even go extinct in the Romanian Carpathians, where the highest altitudes are relatively modest (2,544 m.a.s.l. for the boldest peak).
- 1 Representative Concentration Pathways, as adopted by the IPCC (Intergovernmental Panel on Climate C (...)
- 2 If this increase remains valid, the annual average of -2.2°C resulted for the air temperature at Vâ (...)
3Climate change scenarios for Europe take into account global warming levels (GWL) ranging from 1.5 °C to 4.0 °C compared to the 1850–1900 period. This paper relates to the projections of the RCP4.5 scenario1 relying on the hypothesis of a warming level limited to 3.0 °C (IPCC, 2023). This warming generates ecosystem disruptions in Europe, redistribution of habitat areas within current ecosystems and could change their composition, sometimes in an irreversible manner, with these effects increasing in severity above 2.0 °C GWL (Bednar-Friedl et al., 2022). Within the Southern Carpathians area, an increase of the mean annual temperature of 2.5 °C2 is expected by the year 2100 (Sârbu et al., 2020).
4The upward migration of high mountain plants is primarily the result of climate warming (Parolo and Rossi, 2008), while human intervention in the Alpine region also plays an important role. Timberline (or upper tree limit) is situated at the interface of coniferous forest and subalpine heath (Figure 1), with its current position being the result of both climatic and human influences in the densely settled Carpathians (Shandra et al., 2013). The climate influence on altitude variation of the timberline is not clearly defined due to the impact of past and recent human activity (Czajka et al., 2015) whether it’s about logging, grazing or the abandonment of agricultural activities, extensive since 1990 (Munteanu et al., 2014). On the other hand, using the entire altitudinal range by mountain agroforestry communities has profoundly modified the limits of vegetation levels and lowered the timberline sometimes by 300 to 400 m, as it has been studied in the Ukraine’s Carpathians during the 20th century (Kolischuk, 1958, cited by Shandra et al., 2013). More notable for recent times, the increase of timberline altitude, found at least for the Southern Carpathians in Romania (Mihai et al., 2007) becomes a general trend in mountain areas where the abandonment of agroforestry and pastoral activities takes place at the benefit of tourism activities.
5The vegetal productivity of the alpine belt habitats is very poor (about 0.8 tons/year/ha) compared to that of the subalpine habitats (2.0 to 6.0 tons/year/ha) (Doniță et al., 2005). The maximum productivity of montane forests (11.0 tons/year/ha), currently reached in the altitude range of 1,000 to 1,200 m.a.s.l., is expected to migrate by the end of the century toward altitudes of 1,600 to 1,800 m.a.s.l. (current coniferous zone), with the increase of the spruce trees upper limit by 600 m (Guvernul României, 2016). Contrary to this productivity increase, the biodiversity of plant formations should decrease.
6This paper aims to contribute to the in-depth knowledge of the climate change impact in the Carpathians of Romania, across two main objectives: assessing the sensitivity of six habitats (representative for the Alpine region) to climate change in the next decades and assessing the more or less favourable aspect of the climate evolution in the last decades for three of the six selected habitats. The analysis of the more or less favourable aspect of the climate evolution relies on data historically recorded by weather stations, while the habitat sensitivity analysis is based on climatic future projections performed at the level of administrative division of territory.
7In mountain climates, as in the Romanian Carpathians, under continental and mediterranean influences, plants may be impacted by an increase of evapotranspiration (Beniston, 2003), because of climate warming. From 1961 to 2010, the entire Carpathian region experienced a significant increase in heatwave frequency, average duration and intensity (Spinoni et al., 2015). The RCP4.5 climate change scenario projects a higher intensity of heatwaves over the next decades, both in terms of duration and frequency, especially in the Southern Carpathians area.
8Plant species from the alpine and subalpine belts (Table 1; Figure 1) will be, presumably, the most affected by the rising temperatures and by the heatwaves occurring during sensitive phenological phases, especially the dormant period (Wagner-Lücker et al., 2014). Species whose regeneration buds are protected by the snow layer (as it’s especially the case of chamaephytes, e.g., Draba dorneri, Oxycoccus microcarpus) would be among the most vulnerable to climate change, because of the substantial reduction of the snow cover below altitudes from 1,500 to 2,000 m.a.s.l., projected for Europe during the 21st century, even at a limited GWL (Bednar-Friedl et al., 2022).
- 3 Tozzia alpina ssp. carpatica is associated to the habitat 6230 Species-rich Nardus grasslands.
- 4 Species of lower altitudes would advance to higher altitudes, at the expense of the original specie (...)
9In the alpine belt, flora of Community interest (species mentioned in the “Habitats” Directive) includes some endemic plants for the Romanian Carpathians: Campanula serrata, Draba dorneri, Poa granitica ssp. disparilis, Tozzia alpina ssp. carpatica3, as well as some boreal relics: Ligularia sibirica and Saxifraga hirculus (Ciocârlan, 2009). The geographic distribution of those endemic species might shrink because of the potential competitive advantage of the migrant species from lower altitudes4 and due to the physiological limitation (Hurdu, 2012) they might encounter.
Table 1. Vegetation zones and thermal typology of plant species
Information source: Ciocârlan, 2009
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Figure 1. Altitudinal distribution of vegetation zones in the Romanian Carpathians
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10Half of the Natura 2000 habitats from the category of bogs, mires and fens (including the habitat 7110 Active raised bogs) are potentially impacted by climate changes in Europe (Figure 2 A). The amphibian species are, as well, the most vulnerable group to global warming (Figure 2 B), because of their low adaptive capacity to potentially water-deficient conditions of living.
Figure 2. Percentages of Natura 2000 habitat types by category of plant formation (A) and of Community interest species by specific groups (B), for which at least one EU member state identified climate change as one of the causes for the unfavourable trends in their natural area
Information source: EEA, 2012
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11The study area matches the Alpine biogeographical region in Romania. With a total area of 46,800 km2, this region covers 80.4% of the Carpathians (Strat and Mihăilescu, 2017), a mountain range of recent age (Alpine orogeny), displaying post-glacial landscapes and a variety of constitutive rock formations: crystalline, sedimentary (flysch, limestone) and volcanic rocks. Relatively modest altitudes (up to 2,500 m.a.s.l., except for the highest peaks) imply a narrow alpine belt (with a vertical extension of only 300 to 400 m) that could lead, in the context of global warming, to the shrinking and even the disappearance of treeless formations. In default of the upper nival belt, it is not possible for the current high mountain vegetation to migrate upward, unlike the vegetation in the Alps (Theurillat and Guisan, 2001).
12Romanian Carpathians are suitable for this study thanks to the limited distribution in altitude of species and habitats, some of them being found only in a narrow altitudinal range, as it’s the case of plant formations from the alpine belt. In Europe, around 20% of the native vascular plant species are found in the alpine zone (including the alpine and subalpine belts, between the upper treeline and the snow lower limit), an area that covers only 3% of the European land territory (Gottfried et al., 2012).
13In this study, the analysis of the climate change impact has essentially focused on habitats at the expense of species, the main reason being that the spatial delimitation of the habitats is more precise and their territorial marking is more persistent. Moreover, taking into account the whole plant community of each habitat allows the entire range of environmental factors (geology, soils, climate, water availability) to be integrated.
14This analysis was carried out for a series of priority Natura 2000 habitats because, according to “Habitats” Directive 92/43/EEC, these are “natural habitat types in danger of disappearance” (European Council, 1992). The sensitivity to climate change was assessed for six priority habitats in the Romanian Carpathians, two for each of the three broad categories of plant formations (based on Figure 2 A): bushes and grasslands (habitats 4070 Bushes with Pinus mugo and Rhododendron myrtifolium and 6230 Species-rich Nardus grasslands), bogs and fens (habitats 7110 Active raised bogs and 7220 Petrifying springs with tufa formation) and forested habitats (91D0 Bog woodland and 9180 Tilio-Acerion forests of slopes, screes and ravines), the last two habitats showing transitory characteristics (Table 2).
Table 2. Overview on the studied Natura 2000 habitats
- 5 The overall assessment of the habitat conservation status in the Alpine region (2013-2018) is based (...)
Cumulated area of the habitat totalizes the areas covered by this habitat within the Sites of Community Importance located fully or mostly inside the Alpine region (according to Standard Data Forms).
Conservation status5: Fv = favourable; U1 = unfavourable—inadequate.
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15The cumulated area of the six habitats within the 69 protected areas considered in this study (see Appendix) covers about 1% of the Alpine region of Romania. These habitats are distributed throughout the Romanian Carpathians across the entire range of mountain vegetation levels (Figure 3; Table 1). The diversity of the selected habitat types and their wide distribution, both horizontal and vertical, provide representativeness for the Alpine region.
16Three natural areas protecting the habitats 4070 Bushes with Pinus mugo and Rhododendron myrtifolium, 6230 Species-rich Nardus grasslands and 91D0 Bog woodland were selected for their spatial and altitudinal proximity to the weather stations involved in the study. Moreover, these natural areas are located within three mountain ranges representative of the Carpathians petrographic diversity: Ceahlău massif (in ROSCI0024 Ceahlău, culminating at 1,907 m.a.s.l. on flysch formations); Bucegi massif (made of flysch and limestone, in ROSCI0013 Bucegi, with the highest peak at 2,505 m.a.s.l.); Harghita-Mădăraş massif (located in ROSCI0090 Harghita-Mădăraş, reaching a maximum altitude of 1,801 m.a.s.l. on volcanic rocks). Miercurea-Ciuc weather station is located at the lower limit of the beech subzone, while the mountain stations Ceahlău-Toaca and Vârful Omu are found within the subalpine and alpine belts, respectively. The diachronic data provided by these weather stations reflect the climatic conditions in which these habitats evolved during recent decades, which allowed the assessment of the more or less favourable aspect of both past and current climate (Figure 8).
Figure 3. Geographical distribution of Sites of Community Importance (light green dots) declared for each selected habitat and the biogeographical regions in Romania (Alpine region in pink)
Compiled and adapted from Natura 2000 Network Viewer
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17Based on quantitative assessments and quality analysis of the climatic and human origin of risks and threats to mountain biodiversity, the methodology used in this study focuses on the integration of certain parameters specific to six priority Carpathian habitats from the Alpine region in a formula aiming to assess the sensitivity to climate change for those habitats. The methodology is rather exploratory, with current limitations and future extensions.
18A preliminary database was created in order to gather data and information about the Sites of Community Importance and their characteristics. Geospatial information acquired from Natura 2000 Network Viewer application6 was used for overlapping the distribution of these sites against the biogeographical regions in Romania (Figure 3), in order to better assess the representativeness of the selected habitats that are typical for the Alpine region7. Only those sites included by at least 50% in the Alpine biogeographical region as well as the protected areas declared for at least one priority habitat (according to Standard Data Form) were retained for the analysis.
19The selected Natura 2000 habitats were related to the national habitat types of the Romanian classification system (according to Doniță et al., 2005), in order to apprehend the entire spectrum of ecological ambiances and to define the optimal temperature and precipitation amplitudes that describe the favourable climatic conditions for each habitat of Community interest (Table 3). Subsequently, climatic amplitudes specific to the selected habitats were adjusted according to their altitude extension within the forementioned sites, based on the information from the Management Plans of protected areas (Ministerul Mediului, Apelor şi Pădurilor, 2016) and the geographical characteristics of the timberline in the Carpathians (Czajka et al., 2015). Multiannual variation and trends of mean air temperature and precipitation amounts were graphically represented in Excel against the amplitudes between the maximal and minimal values specific to each priority habitat (Figure 8).
Table 3. Altitude and climatic amplitudes of the selected habitats
dMI: de Martonne Index
Values adapted from Doniță et al., 2005
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20The variability and trend analysis of annual mean temperature and precipitation amounts recorded at three weather stations, representative for the Alpine biogeographical region (Figure 4), was performed in Excel using climate data available in the European Climate Assessment & Database (Klein Tank et al., 2002). These data allowed the assessment of the more or less favourable aspect of the climate in the case of three habitats among the six involved in this study.
Figure 4. Geographical location of selected weather stations within the Alpine region of Romania
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- 8 Results within the project “Consolidarea capacității instituționale pentru îmbunătățirea politicilo (...)
21The assessment of the climate change sensitivity was performed for the six priority habitats based on specific criteria, including the future change analysis (according to the RCP4.5 scenario) for a set of climatic indicators determined at the level of administrative division of territory8. These units were overlapped with the spatial distribution of the selected habitats for a higher fidelity of the climate change signal in the Alpine region.
22In order to assess the sensitivity level of the habitats to climate changes, six parameters were taken into account for their relevance to the characteristics and to the optimal ecological conditions of each habitat (according to tables 2 and 3):
Am: Average area of the habitat within the Sites of Community Importance; wider areas (on average) of the sites mean potentially a higher stability of the habitat against threats and perturbations from the outside.
Sc: Conservation status of the habitat in the Alpine region of Romania (Table 2).
ΔH: Amplitude of the habitat altitude (the narrower the vertical extension, the more vulnerable the habitat is to the invasion by competitive species, in the context of climate change).
Tmax: Maximum temperature of the habitat optimum; this parameter measures both the sensitivity of the mountain habitats to global warming or, if exceeded, their supportability.
Δt: Optimal amplitude between maximum and minimum temperature (the wider the thermal amplitude, the higher the adaptive capacity of the habitat).
ΔCC: Variation of the key climatic indicator for the habitat, in the perspective of climate changes (Figure 5).
Figure 5. Evolution of the relevant climatic indicators by the end of the 21st century (according to the RCP4.5 scenario). Basis for the ΔCC parameter assessment (see Figure 6)
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23The most crucial but also the most uncertain component in the sensitivity formula is the ΔCC parameter, the future climatic conditions having a strong influence on habitat evolution. Scoring this parameter takes into account the decreasing/increasing trend of the key climatic indicator (projected values of air temperature, precipitation amount or de Martonne Index) for the 2071–2100 period compared to the reference period of 1971–2000 (see Figure 5). The ΔCC parameter describes the more or less favourable aspect of the potential climate evolution for a habitat over the next decades.
Figure 6. Matrix for the assessment of the habitat sensitivity
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24In the Alpine region, climate changes might become favourable for some plant formations. For instance, if the precipitation increases (Figures 5 C and 5 D), there will be a null or even a negative score for the parameter ΔCC that will not count in the final score or it will even contribute to its decrease and eventually to a lower climate change sensitivity for that habitat.
25Stronger or weaker dependence of each habitat on a particular level of humidity was assessed as following: low dependence for the habitats 4070 Bushes with Pinus mugo and Rhododendron myrtifolium and 6230 Species-rich Nardus grasslands; moderate dependence for the habitats 91D0 Bog woodland and 9180 Tilio-Acerion forests of slopes, screes and ravines; high dependence in the case of the habitats 7110 Active raised bogs and 7220 Petrifying springs with tufa formation, for which the precipitation amount was taken into account as a key indicator. For the habitats 4070 and 6230, the mean air temperature was set as a key factor, while in the case of the habitats 91D0 and 9180, it was the Aridity Index de Martonne which was considered as essential.
26De Martonne Index (dMI) resulted from precipitation amount (Pp) and air temperature (T), for each time interval (Figures 5 E and 5 F), placing these habitats in the “extremely humid” and “very humid” areas (according to Croitoru et al., 2013) of the Romanian territory.
- 9 The weighting factors of the parameters in the formula were set following a ranking based on the pr (...)
27Based on the assessment matrix (Figure 6), the scores given for each parameter9 were put in the following formula of calculation:
28The final climate change sensitivity score (Ss) could fit in one of the following five levels of sensitivity: neutral (≤ 1.25), low (1.26… 2.00), moderate (2.01… 2.75), high (2.76… 3.50) and critical sensitivity (> 3.50).
29The selection of parameters used in the formula from above takes into account mainly the biotope features related to the climatic conditions specific to each habitat. Another study on the alpine habitat sensitivity (Sârbu et al., 2020) proposes an approach based on ecological indices for plant species of Bucegi Mountains in the Southern Carpathians.
30Assessing the sensitivity of habitats to the impact of climate change considered many aspects, primarily based on the general description provided for each of the six habitats (Table 2).
31Habitat 4070 Bushes with Pinus mugo and Rhododendron myrtifolium is the most extensive, with the greatest area occupied in the site ROSCI0085 Frumoasa, where the 4,000 hectares are shared between three massifs within the Southern Carpathians. In this protected area, juniper groves are fragmented by dense trail networks (Management Plan of the site ROSCI0085) which resulted from overgrazing. This current pressure represents an additional sensibility factor to climate change and could damage the long-term resilience capacity of the habitat.
32Species-rich Nardus grasslands, constitutive of the habitat 6230, cover the most important area (3,002 ha) in the site ROSCI0323 Munții Ciucului where the most extensive hayfields from Eastern Carpathians (Standard Data Form) keep being used as such, supporting a traditional and sustainable activity.
- 10 The two bog habitats share also some boreal relics: Andromeda polyfolia, Empetrum nigrum, Oxycoccus (...)
33The distribution of the habitats 7110 Active raised bogs and 91D0 Bog woodland, frequently associated within the same protected areas because of their local interferences10 (Table 2), is centred on the Eastern Carpathians (Figures 3 C and 3 E). This is where is found, among others, the site ROSCI0086 Găina-Lucina, specific for both genetical and evolutionary connections between the two habitats.
34Most of the petrifying springs with tufa formation are located in natural areas also protected for Tilio-Acerion forests of slopes, screes and ravines. Between the two habitats, codified respectively 7220 and 9180 (the latter being situated at lower altitudes), there is a relation supported by the presence of the limestone bedrock, specific for both of them (Table 2), as it’s the case of the site ROSCI0126 Munții Țarcu (see Appendix).
Figure 7. Box plots of the areas (≥ 1 ha) covered by the selected habitats within the Sites of Community Importance in the Alpine region
Values processed from Standard Data Form
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35More severe heatwaves and higher rainfall rates are expected in Romania by the end of the century, according to the RCP4.5 climate change scenario. Subalpine and alpine bushes and grasslands (including habitat types 4070 Bushes with Pinus mugo and Rhododendron myrtifolium and 6230 Species-rich Nardus grasslands) strongly depend on low temperatures and a significant snow cover (70 to 80%) during the cold season. Therefore, the characteristic plant species (hekistothermophytes, psychrothermophytes) are very sensitive to the climate warming that could generate thermal stress and especially a very strong competition of forest species whose upward migration will be fostered. Otherwise, woodland habitats are potentially more sensitive to drought (Sârbu et al., 2020).
36For the species of flora and fauna adapted to cold climate, extreme temperatures could become either a short-term threat (because of stronger heatwaves and thermal amplitudes recorded in shorter time intervals) or a long-term threat, in the broader context of global warming.
37Global warming contributes to the amplification of extreme climatic events (Table 4), whose intensity and frequency could become unprecedented. This could damage or even remove small habitats from certain areas and extinguish some of the already vulnerable species. These changes could also lead to a wide redistribution of ecosystems: today’s alpine belt would show in the future a mosaic of subalpine and alpine elements (Theurillat and Guisan, 2001).
Table 4. Climate-related natural events with potential impact on biodiversity in the Romanian Carpathians
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38Thermal conditions of the local climate have been rather favourable since the year 2000 for the habitat 4070 Bushes with Pinus mugo and Rhododendron myrtifolium (Figure 8 A), as proved by its favourable state of conservation and its extension in the site ROSCI0024 (Ceahlău National Park Management Plan, 2016). If the increase of the air temperature recorded at Ceahlău-Toaca weather station since 1964 is confirmed as a long-term trend by the climate models, the upper limit of the thermal optimum of the habitat 4070 will be exceeded over the next decades.
39At Vârful Omu, precipitation amounts varied widely compared to the average of the 1961–2019 period, reaching as low as 400 mm/year, well below the minimum required for the habitat 6230 Species-rich Nardus grasslands (Figure 8 D), while at Ceahlău-Toaca and Miercurea Ciuc rainfall fluctuated over the entire analysis period at levels underneath the lower limits of the habitats 4070 Bushes with Pinus mugo and Rhododendron myrtifolium and 91D0 Bog woodland (Figures 8 B and 8 F).
40Vârful Omu station is found at around 2,500 m.a.s.l., above the higher limit of the habitat 6230 (see Table 3). Therefore, in Figure 8 C, temperatures recorded at this station were lower than the theoretical minimum of the habitat 6230 over most of the analysis period from the 1960s until the end of the 2000s. After 2011, the variation curve entered into the specific amplitude range, following the upward trend also shown in Figure 5 B, with the starting point set at 6 °C (the higher limit of the same optimal amplitude). This is the average temperature (1971–2000) computed for the administrative divisions covered by the habitat 6230 Species-rich Nardus grasslands and it stands well above the mean value of -2.5 °C resulted for Vârful Omu station over the same period of time.
Figure 8. Variation of the air temperature (T°C) and precipitation amount (Pp) at weather stations against the adjusted specific amplitudes for the selected habitats
Climate data source: Klein Tank et al., 2002
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- 11 Located at almost 1900 m (see Figure 4), the mean altitude of the habitat 4070 Bushes with Pinus mu (...)
41Even if the climatic data recorded at Ceahlặu-Toaca station11 show a rainfall variation curve always lower than the theoretical minimum required for the habitat 4070 Bushes with Pinus mugo and Rhododendron myrtifolium (see Figure 8 B), the projected increase in precipitation amount during the next decades would provide more humidity for this habitat currently assessed as highly sensitive (Table 5)—although rainfall was not considered as a key factor for the viability of these alpine bushes with low water dependence. Nevertheless, in a warmer climate, higher soil humidity would be subjected to a more intense evaporation that would decrease the potential water surplus in mountain ecosystems. In the next decades, the projected increase of air temperature will sustain the transition to an increasingly less humid climate, reflected by the decrease of the de Martonne Index (dMI), with impact particularly on the forested habitats (Figures 5 E and 5 F).
Table 5. Assessment of the climate change sensitivity for the selected habitats
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42The highest climatic sensitivity resulted for the habitat 4070 Bushes with Pinus mugo and Rhododendron myrtifolium (Table 5), because of its narrow thermal and altitudinal amplitudes (parameters Δt and ΔH).
43The habitat 7110 Active raised bogs seems to be the least sensitive to climate change, despite its unfavourable—inadequate state of conservation (U1). The ΔCC parameter, translated in this case into a slight increase in rainfall projected for the next decades, plays a major role in dragging down the final score of this habitat to the lowest level among all the selected habitats.
44Another low-sensitive habitat is 6230 Species-rich Nardus grasslands: despite its narrow horizontal extension in terms of individual area within each protected site (Figure 7), it has the advantage of a broad vertical extension (ΔH = 1,540 m in Table 5), being eventually more resilient to climate change, especially since its previous and prospective favourability is supported by the recent rainfall and thermal regimes that are close to the specific climatic amplitudes of this habitat, at least in the Bucegi Mountains (see Figures 8 C and 8 D).
45In the case of the habitat 7220 Petrifying springs with tufa formation, moderately sensitive and highly dependent on water resources, the provision of a hydrological regime whose seasonal contrasts don’t deepen is a challenge for its conservation in a changing climate. Usually, the isolation of this habitat with dotlike distribution within the protected areas makes it less vulnerable to the impact of human intervention, thanks to its self-conservation capacity.
46The rise in the frequency and intensity of rainstorms would increase the washout processes and the risk of shallow landslides in the Alps and the Carpathians (Gariano and Guzzetti, 2016). The habitat 9180 Tilio-Acerion forests of slopes, screes and ravines is, by its nature, particularly vulnerable to landslides and has already a climatic sensitivity score of 2.33 (the second-highest score among the selected habitats).
47The proposed method for the habitat sensitivity assessment could be subjected to further improvement and to future extension for other habitat types. The level of sensitivity to climate changes could be assessed in terms of altitudinal gain for plant species and of area loss for habitats (ha/decade), following an analysis that takes into account other factors potentially influencing the medium-term stability of habitats, such as the risks of soil erosion, landslides, wildfires or other climatic events (inventoried in Table 4).
- 12 The selection of the weather stations was limited to those with available data.
48The distances between the sites containing the selected habitat areas, scattered in different mountain ranges, and the three weather stations covering only the eastern part of the Romanian Carpathian arch12, did not allow a spatial generalization of the climatic data for the entire study area. Therefore, the analysis of the more or less favourable aspect of the climate was limited to only three habitat types, each included in a site located near one of the three weather stations. An extended dataset, available also for stations from the Southern and Western Carpathians areas, could allow a more robust assessment of this more or less favourable aspect of the climate for the habitats in the last decades.
49Refining the weighting factors of the input parameters in the formula of sensitivity would require the opinion of experts coming from different fields in order to have a more consistent approach on the importance of each indicator. The habitat sensitivity also depends on the shape of the protected site (for example, an elongated and narrow shape is more vulnerable to external influences than a rounded one), but this feature could be retrieved only by a precise mapping of the habitat distribution on the field and by a diachronic analysis of remote sensing images.
50This research, which is based mainly on climatic and biogeographical data, would require to be extended by fieldwork sessions for the assessment of the current state of habitats and of their level of sensitivity for the result validation (see Table 5). Furthermore, simulations with different inputs and weighting factors in the applied sensitivity formula, while also taking into account the human pressures and threats, could eventually provide better assessments, in accordance to field observations.
51Climate change, to which the Romanian Carpathians show a certain specificity, will exert more stress on the already threatened species, making them even more sensitive to its different effects (climate warming, thermal contrasts, fluctuation of rainfall regime, etc.). As a result, many species populations of alpine flora with narrow ecological amplitude could become scarce or even disappear, due to the degradation of the bioclimatic conditions allowing their optimal development.
52Climatic changes will have a differentiated impact on the Carpathian habitats: the highest habitat (4070 Bushes with Pinus mugo and Rhododendron myrtifolium) and the two forested habitats (91D0 Bog woodland and 9180 Tilio-Acerion forests of slopes, screes and ravines) would be the most sensitive to climate change.
53Due to the relief that is generally more fragmented, Carpathians are relatively more easily accessible to human intervention than the Alps. Therefore, the current and future effects of the climate change impact on the Carpathians biodiversity could be exacerbated while being mitigated by several pre-emptive measures against environmental pollution, wildfires, overexploitation of natural resources, landscape fragmentation and spread of invasive species, in order to relieve the habitats and species from the non-climatic pressures exerted on them.