Habitat change has been dramatic in some mountain environments and occurs in different forms (e.g., urban and agricultural expansion/land abandonment) (Figure 1). The drivers of change imposed by recreation and tourism are changing mountains dramatically (e.g., land-use change, habitat fragmentation, conflicts with wildlife, noise, air and soil pollution, greenhouse gas emissions, land degradation, i.e., erosion). This has been observed in the Alps (e.g.; Orsi et al., 2020), Pyrenees (e.g., Badoque et al., 2017), Himalayas (e.g., Yang et al., 2021), Tatra mountains (Fidelus-Orzechowska et al., 2021), to mention some. For instance, Skiing resorts development has a detrimental impact on soil properties, vegetation distribution, biodiversity (Hudek et al., 2020), geomorphological features (Wrońska-Wałach et al., 2019) and wildlife (Stott et al., 2019). Another popular activity that is changing mountain habitats is mountaineering (e.g., climbing, trekking, hiking, biking) (Apollo, 2021). Several works highlighted that the climbers, hikers and bikers are altering land relief and soil (e.g., soil erosion), vegetation and grazers behaviour, animal feeding grounds, and increasing trail degradation, litter and excrement pollution (e.g., Apollo & Andreychouk, 2020; Evju et al., 2021). Although recreation and tourism activities are beneficial for local economies, retain people in rural areas and favour the development of outdoor activities important for human wellbeing (Hanna et al., 2019), there are important tradeoffs associated with the loss of regulating ES, such as global and local climate regulation (Delgado et al., 2007), air quality regulation, water purification, flow and nutrient regulation (e.g., Ristic et al., 2012), natural hazards regulation (Arnaud-Fassetta et al., 2005) and pollination (e.g., grassland flora diversity, Bacchiocchi et al., 2019). The expansion of ski resorts has a strong impact on the conversion of grasslands and agricultural areas to the urban fabric, decreasing the capacity of these ecosystems to supply biomass for energy and food (García-Ruiz & Lasanta, 1993; Theobald et al., 1996), respectively. Also, negative impacts were identified on the local cultural activities (Pickering et al., 2003).

In several mountains of the world, such as in the Peruvian Andes (Tovar et al., 2013), Ethiopian highlands (Kidane et al., 2012) or Thailand (Choenkwan et al., 2014), the pressure for food security and increasing market demand, are increasing the agriculture area expansion. The agriculture intensification in mountain areas can be profitable in the short term regarding food production and can support recreation and tourism activities. Nevertheless, agriculture intensification may have negative impacts on the ecosystems capacity to regulate the climate and the air quality (e.g., Cai et al., 2019), water purification, flow, erosion and nutrients (e.g., Rukundo et al., 2018), natural hazards (e.g., Erena & Worku, 2018) and pollination (e.g., Ritten et al., 2018). Although there has been observed a trend in the increase of mountain areas agriculture, others have been affected by land abandonment, a complex socio-ecological phenomenon observed in several mountain areas of Europe (Lasanta et al., 2017) and Asia (Han & Song 2019). Land abandonment imposes an important disturbance in mountain ecosystems, which can have positive or negative impacts. Associated with land abandonment is the rewilding process that favours several regulating ES such as global and local climate regulation, through the increase of carbon sequestration (e.g., Bell et al., 2020) and water purification, erosion and nutrient regulation (e.g., Lizaga et al., 2018) and biomass for energy and timber (e.g., Pitman & Peace, 2021). As a consequence of vegetation encroachment, there is an increase in plant water consumption, evapotranspiration, consumption and storage. This reduces water flow and the quantity of water that reaches rivers (Khorchani et al., 2021) and aquifers (Ouyang et al., 2021). Afforestation reduces the probability of flash floods and landslides (e.g., Dittrich et al., 2018; Hu et al., 2021). On the other hand, land abandonment and vegetation encroachment increase the fuel available and risk wildfire occurrence (Palaiologou et al., 2017). Regarding the impacts of land abandonment/afforestation on natural hazards regulation, there is an important tradeoff between flood/landslides mitigation and wildfire risk. To mitigate this, it is essential to establish fuel management policies (e.g., prescribed fires) to reduce fire risk without compromising flood regulation (Pereira et al., 2021). Land abandonment decreases the capacity of mountain areas to provide food. In this process, traditions, cultural activities and landscapes are lost (e.g., Hanaček & Rodríguez-Labajos, 2018). For instance, one of the most evident impacts is the agricultural terraces destruction due to lack of maintenance (Stavi et al., 2018). The destruction of these structures can trigger soil, water losses, floods and landslides (e.g., Moreno-de-las-Heras et al., 2019).

Dam construction for hydropower production dramatically impacts freshwater habitats fragmentation, river ecological function and thermal regimes, nutrient and sediment flux and biodiversity loss (Vuong Pham et al., 2019; Barbarossa et al., 2020). Although these infrastructures increase the amount of energy produced from renewable resources, they have profound impacts on fish spawning migratory routes and affect the communities that depend on this resource for food supply (Dugan et al., 2010). Also, wind farms imposed a high disruption in the environment, and several works highlight that they disturb the natural habitats strongly and negatively affect the different trophic levels (e.g., Thaker et al., 2018; Fernández-Bellon et al., 2019). These infrastructures have negative impacts on recreation and tourism (Ólafsdóttir & Sæþórsdóttir, 2019), landscape aesthetics, noise (Kalinauskas et al., 2021) and cultural heritage (Nazir et al., 2020). Finally, as the previous renewable energy resources, solar energy may impose a negative impact on habitats loss and reduce the habitats for pollinators (e.g., McCoshum & Geber, 2020) and landscape aesthetics (e.g., visual quality) (Dhar et al., 2020).

Climate change (e.g., glacier melting, extreme events, and drought periods) negatively affects mountain ecosystems and their capacity to supply services (Figure 1). Although all ES are predicted to be affected, the most relevant impacts are expected in global and local climate regulation, natural hazards regulation, crops, wild food and fish provisioning, freshwater provisioning, renewable energy, recreation and tourism, landscape aesthetics and cultural heritage and cultural diversity (Palomo, 2017; Hua et al., 2021).

Mountain ecosystems are highly vulnerable to small changes in the climate (e.g., Iglesias et al., 2018) and, therefore, to ecosystem change (e.g., tree-line upward) (Cazzolla Gatti et al., 2019). This will likely affect carbon sequestration (global and local climate regulation) (Hua et al., 2021). As a consequence of glacier and permafrost melting and increase in extreme events, natural hazards (e.g., flash floods, landslides, rockfall) are expected to be more frequent and severe (e.g., Terzi et al., 2019; Viani et al., 2020). The increase of wildfires frequency can amplify the high vulnerability to natural hazards, severity and recurrence in a climate change context (e.g., Taboada et al., 2017; Cassell et al., 2019). High temperatures and the prevalence of long and frequent drought periods are expected to increase the vulnerability to wildfires. Severe and recurrent wildfires are the ones that impose more ecosystems damage and affect drastically the ecosystems capacity to recover. Therefore, the expected increase of severe wildfires may trigger other natural hazards such as flash floods (e.g., Nolan et al., 2018; Coscarelli et al., 2021).

The alteration of temperature and precipitation patterns due to climate change will affect the water availability (e.g., glacier melting, reduced snow cover, drought periods) for food production in mountain communities (e.g., Poudel & Duex, 2017), but also in lowland areas that depend on water from glacier and snow melting to irrigate their fields (Huss et al., 2017). Also, climate change impact on ecosystems shift will affect the distribution of wild foods such as berries (Prevéy et al., 2020) and mushrooms (Yang et al., 2012). This impact on mushrooms productivity in some mountain ranges (e.g., Prades Mountains, Catalonia-Spain) will be negative (Karavani et al., 2018). Climate change will also affect adversely mountain grasslands (e.g., afforestation) (Schirpke et al., 2017). The sensitivity to climate change increases with the increasing altitude (Li et al., 2019a), which will have implications on their capacity to supply food for cattle.

Climate change is also expected to negatively impact hydropower energy, mainly due to the snow and ice cover decrease and the reduced glacier volumes that will negatively affect runoff and energy production. These harmful impacts are mainly identified in dry areas, such as central Asia or the tropical Andes, where runoff volume depends on glacier melting (Huss et al., 2017). Decreases in hydropower production were also observed in other regions such as California (Forrest et al., 2018), Brazil (Oliveira et al., 2017) or Portugal (Teotónio et al., 2017). On the other hand, in regions where precipitation is expected to be high (e.g., Three Gorges Reservoir - China), hydropower energy will increase (Qin et al., 2020).

Climate change has a negative and positive impact on mountain recreation and tourism. Winter sports will be negatively affected by the decreasing number of days with snow and ice cover (e.g., Fang et al., 2021). Several solutions have been established to tackle this problem, such as show snowmaking. However, this solution increases energy and water demand (Rixen et al., 2011) and has negative impacts on mountain ecosystems (Wrońska-Wałach et al., 2019). Glacier tourism is also being affected since most mountain glaciers are disappearing, bringing substantial losses to this industry (Wang & Zhou, 2019). Other phenomena related to climate change, such as the wildfire risk increase, discourage tourists from travelling to these areas (Pereira et al., 2021). However, mountain tourism can benefit during heatwave periods, where people can look for refuges in high altitude areas. Finally, climate change and the impacts on seasonality can affect the time when tourists visit mountain areas (Palomo, 2017).

The disappearance of mountain glaciers decreases landscape aesthetics since tourists highly appreciate this landscape, as observed in previous works (e.g., Welling et al., 2020; Salim et al., 2021). The increasing wildfire frequency will decrease temporarily landscape quality and the attractiveness of these areas to be visited (Pereira et al., 2021). Around the world, several mountain landscapes are sacred for different communities located in the Meili Snow Mountains of Yunnan (China), Nepalese Himalaya, Peruvian Andes, Alaska or Canada. The loss of these glaciers will have a detrimental impact on the communities living in these areas (Allison, 2015; Thornton et al., 2019).

Mountain environments are subjected to high overexploitation, threatening biodiversity and ES supply (Figure 1). For instance, hunting and poaching practices cause biodiversity loss in some mountainous areas (e.g., Adhikari et al., 2021). The mineral resources demand increases the landslides, debris flow, collapse, and ground deformation and subsidence, with severe implications for the populations living in lowland areas (Shao, 2019). Mineral exploitation imposes a high degradation in the areas where they are established by removing soil and vegetation, drastically hampering these ecosystems’ capacity to supply regulating, cultural and other provisioning services (e.g., food, freshwater). Overall, these activities impose a high ES value loss (Dawen et al., 2018).

Overgrazing is another threat to regulating (e.g., global and local climate regulation, water purification, flow, erosion and nutrient regulation, pollination) and provisioning (e.g., food for livestock) ES (Figure 1). This has been identified in several mountain areas of Ethiopia (Mekonen, 2020), China (Hao et al., 2018), Greece (Fetzel et al., 2018) and Central Asia (Nowak et al., 2020), to mention some. For instance, overgrazing reduces the grassland capacity to store carbon (e.g., Zhou et al., 2020), grassland biodiversity (e.g., Nowak et al., 2020), increases soil and nutrient loss (e.g., Zheng et al., 2017; Li et al., 2019b) and reduce pollinators abundance (Naeem et al., 2019). Mountain Forest overexploitation (e.g., timber production) is also a reality in several environments (e.g., Payne et al., 2020), imposing a degradation in the capacity of these ecosystems to regulate global and local climate, air quality (Rawat et al., 2021), water purification, flow, erosion and nutrient regulation (e.g., Negash et al., 2021), natural hazards and pollination. It also negatively impacts non-timber products (e.g., Soe & Yeo-Chang, 2019), landscape aesthetics, and cultural heritage (e.g., Zeb et al., 2019) since several of these areas are considered sacred.

Agriculture intensification in mountain environments also implies a natural resources overexploitation (e.g., water), and it is responsible for soil quality degradation (e.g., von Westarp et al., 2004), changes in pedogenesis process (Tang et al., 2019), erosion (West et al., 2015) and deforestation (Munwar & Udelhoven, 2020). Although agriculture intensification and resources overexploitation may have some short-term positive impact on food production, it has crucial tradeoffs related to global and local climate, air quality and regulation (Ali et al., 2017), water purification, flow, erosion and nutrient regulation (Locatelli et al., 2017), pollination (Christmann et al., 2021), freshwater supply (Rolando et al., 2017), recreation and tourism (Locatelli et al., 2017), landscape aesthetics and cultural heritage (Albizua et al., 2019). Mass tourism expansion increases overexploitation (e.g., Ganie et al., 2019; Mateusz, 2021). For instance, unregulated tourism harms the overexploitation of medicinal plants (Ganie et al., 2019), fuelwood (Laiolo et al., 2004) and water (Singh et al., 2020) in the Himalaya. In the Mediterranean mountains, mass tourism is causing an increase in groundwater exploitation (Pulido-Bosch et al., 2020).

Mining activities are responsible for high levels of soil and water resources pollution (in the site and off-site) in several mountains of the world, located in Asia (e.g., Wang et al., 2019), North America (e.g., Lemly, 2019), Europe (e.g., Kupková et al., 2018), Africa (e.g., Khelifi et al., 2021) and Australia (e.g., Ali et al., 2017) (Figure 1). The overexploitation of mineral resources is one of the most important causes of land degradation (Gabarrón et al., 2019). Mining harms all the biotic ES 1) regulating (global and local climate; air quality; natural hazards; pollination) and 2) provisioning (crops, livestock, wild food and fish, biomass for energy and timber and freshwater) since mining exploitation involves vegetation and soil removal (e.g., Lee et al., 2017; Rajan, 2019) and increase waterbodies pollution (e.g., Santana et al., 2020). Also, the mining industry affected negatively cultural heritage in several countries (e.g., Ghana and Western Australia) (Apoh et al., 2017). Paradox to the above mentioned, there is a growing interest in preserving old mines as part of cultural landscape and history in some regions (e.g., Pardo Abad et al., 2017).

Agriculture intensification increases soil and water pollution (e.g., agrochemicals, microplastics) (Ennaji et al., 2020; Feng et al., 2021), and this has been observed in several mountain areas (e.g., Wu et al., 2020; Li et al., 2021). Although some benefits are obtained from crop production, agriculture intensification and the impacts on soil are decreasing their capacity to regulate nutrients, and there are high losses through overland flow (e.g., Strohmenger et al., 2020). It is also well known that agrochemicals harm plants flowering and pollinators (e.g., Dupont et al., 2018), reduce freshwater quality (e.g., Loecke et al., 2017) and decrease the waterbodies capacity to supply fish due to diffuse pollution (e.g., Godinho et al., 2019).

The development of tourist infrastructures in mountain areas increases the pollution and greenhouse gases emission (Jamnongchob et al., 2017) due road development, traffic increase (Sundriyal et al., 2018), infrastructure construction, waste production (Semernya et al., 2017) and litter in wildland environments (Hu et al., 2018). Although for the region, this can represent an increase in recreation and tourism activities. It will have important tradeoffs on other ES such as air quality regulation, pollination and freshwater supply (Sundriyal et al., 2018; Kamel, 2020).

Invasive species in mountain environments are a consequence of multiple human impacts such as land-use change (e.g., plantations), nitrogen deposition and tourism development (e.g., infrastructure development) (Figure 1). Other aspects such as the herbivores abundance, pests and diseases, wildfires or landslides have implications on plants distribution. Climate change has direct (e.g., productivity, competitive balance, phenology) and indirect (e.g., changes in hydrological regime) impacts on plant distribution. Although the invasive species spread in mountain areas is not so easy as in other ecosystems due to climate conditions, when alien species pass this filter, it is complicated to manage and reverse their spread due to the complex topography. Invasive species in mountain environments is a global phenomenon and are mostly of agricultural origin (McDougall et al., 2010, 2011; Kueffer et al., 2013).

For instance, the proliferation of Eucalyptus spp. (a native specie from Australia) for timber production in several mountains of the world has dramatic impacts on the environment. This specie is planted in all the continents i.e., Africa (Piiroinen et al., 2018), America (Durán et al., 2017), Europe (Oliveira & Tome, 2017) and Asia (Chen et al., 2021). Eucalyptus ssp. plantations are well known to have a high-water consumption than the native forests (White et al., 2021), reduce biodiversity (Deus et al., 2018), increase soil degradation (Banfield et al., 2018) and the vulnerability to wildfire risk (Nunes, 2012). Rubber, palm oil plantations are other invasive species that cause high land degradation in mountain areas (e.g., Leite et al., 2018; Vijith et al., 2018).

Tourism development is an important cause of plant invasion. For example, hiking trails and roadsides are considered major paths of alien plants spread in mountain areas (Liedtke et al., 2020). Also, the introduction of species of fish (Tiberti et al., 2019) and herbivores (Martín-Esquivel et al., 2020) in high lands dramatically impact native fauna. There are several examples where the introduction of non-native herbivores leads to a very high environmental degradation (e.g., sheep in Iceland, Barrio et al., 2018).

Finally, climate change is expected to increase invasive species spread in mountain areas. However, this is a more serious problem in low land areas. Since mountain areas have a harsh climate, the alien species spread is difficult. However, climate change may favour the environmental conditions required for non-native species that affect high altitudes (Petitpierre et al., 2016). In addition, as mentioned previously, with climate change, it is expected that wildfires will be more severe and frequent, increasing the risk for plant invasion, as observed in previous works (e.g., Reilly et al., 2020).

Several studies have been developed about the impact of invasive species on ES (e.g., Vilà & Hulme, 2017; Rai & Singh, 2020). There are several tradeoffs involved in the impacts of invasive species in mountain environments. Forest plantations can have some benefits in the production of biomass for energy and timber. However, they have a low capacity to regulate global and local climate than native forests (Yu et al., 2019). Therefore, the establishment of non-native species plantations cannot be considered an advantage. Plantations affect the capacity of the ecosystem dramatically to regulate water flow, erosion and nutrients - mainly in young plantations - (e.g., Liu et al., 2017), pollination (Potts et al., 2010), freshwater supply (León-Muñoz et al., 2017) and recreation and tourism (Benra et al., 2019). Climate change impact on invasive species is expected to affect native pollinators negatively (e.g., Schweiger et al., 2010; Silva et al., 2021).