Keywords

1 Introduction

The steppe is a dry, cold terrestrial ecosystem, where herbaceous, graminoid, and shrub species dominate. In the south of South America they extend through the Argentine Patagonia, from the coasts of the Atlantic Ocean to Chile, where they are restricted to the rain shadow zone to the east of the Andes Range in Aysén and Magallanes, except in Tierra del Fuego where they occupy the driest central-northern sector of the island [27]. These steppes develop in a semi-arid continental climatic regime, in which despite summer rainfall, evaporation usually exceeds precipitation [1]. The cold steppe ecosystems, dominated by grasses of the genera Stipa, Festuca, and Poa, would have reached their greatest development during the Late Pleistocene, due to the cold, dry climate that prevailed during that era [36]. Paleoecological records suggest that the steppe was the predominant ecosystem in vast areas of the planet during the Last Glacial Maximum (ca. 18,000 years BP) [36]. Steppe ecosystems have continental-type climates, as most of these environments are associated with large territories and mountainous areas with little oceanic influence [85]. Steppes have high seasonal climatic variability,summers are generally dry and warm, but winters are long and cold [85]. Being arid ecosystems, they have in common water as a limiting factor for the development of vegetation, with rainfall that generally does not exceed 400 mm yr−1 [85].

Stressors to an organism can affect its distribution; humidity and temperature are the main limiting stressors for vegetation in the steppes [2]. Water availability and temperature interact to determine boundaries for different plant communities globally,steppes occupy a specific place in a scheme of global biomes according to the interaction of these two physical factors (Fig. 1).

Fig. 1
An illustrative plot of temperature versus water availability plots 11 landscapes ranging from warm to cold temperature and dry to wet water availability. Tropical desert is the warmest and driest, cold desert, the coldest and driest, and rainforest, the wettest and warmest.

Source modified from Bidwell [2]

General relationship between the types of plant communities or biomes and the conditions of temperature and water availability, indicating the position of the steppes.

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The incidence of livestock in managed steppe is diverse and ranges from extensive pastoral production systems to intensified systems [21]. Both the Northern Hemisphere steppes and the Patagonian steppe sustain extensive livestock use where large volumes of livestock are concentrated, especially sheep and goats [21, 50, 58]. Livestock management in the steppes of southern Chile is sedentary, although with winter and summer rotations [58]. There are differences and similarities between the steppes of Chilean Patagonia and those of other parts of the world, related to climatic variables, soil type, and dominant vegetation (Table 1).

Table 1 Similarities and differences in climate and flora characteristics between the Chilean Patagonian steppe and the Eurasian, Spanish, and North American steppes
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2 Scope and Objectives

The objective of this chapter is to analyze the geographic distribution of the steppe in southern South America, along with the physical (soil and climate), and biological (vegetation and fauna) characteristics of these ecosystems represented in Chilean Patagonia. The chapter describes how the environmental functions and benefits of this ecosystem have been exploited to date for human beings, especially for livestock development, and discusses the main threats to its integrity and future, primarily due to the consequences of climate change, frequency of fires, intense livestock use, expansion of tourism, and invasive species. Comparisons of climatic and vegetation conditions are presented in the main precipitation and temperature gradients that distinguish the northern and southern, western and eastern zones of the geographic range of the Chilean Patagonian steppe.

3 Physical and Biological Characteristics of Steppe Ecosystems, Considering Threats and Ecosystem Services

3.1 Spatial Distribution of the Patagonian Steppe in Chile

The Patagonian steppe is a biome—though also classified as an ecoregion [54]—that is widely distributed in south-central Argentina, and found only in some restricted geographic areas of extreme southern Chile, where it is always in the rain shadow east of the Andes Range [58, 27, 67].

The Chilean steppe ecosystem is located in the regions of Aysén del General Carlos Ibáñez del Campo (Aysén Region) and Magallanes y de la Antártica Chilena (Magallanes Region), on the eastern slope of the Andes Mountains. In the Magallanes Region it is also found in the northern sector of the large island of Tierra del Fuego [58, 67]. The Chilean Patagonian steppe extends from 44° 43' S–68° 42’ W to 54° 06’ S–73° 80’ W, in the eastern fringe of the binational steppe macrozone, which is the wettest area of its distribution.

Different authors have estimated different surface areas for the Chilean Patagonian steppe (e.g. [51, 57], because different variables such as climate, soils, vegetation, or combinations of these can be taken into account [56]. The main characteristic of the steppe is its dominant graminoid, tough herbaceous plant community without the presence of trees, although it may include shrubs [58]. The dominant biomass of the herbaceous vegetation is provided by the perennial grasses that form dense clumps called tussock grasses (in Spanish coirones). The characteristic species in Aysén is Festuca pallescens, while in Magallanes, F. gracillima dominates [58], both species are present transversely in the different soil and climatic conditions mentioned above. Tussock grasses are usually present in all steppe environments, sometimes with low dominance values, including areas where hygrophilous species dominate and coirones may be absent, due to topographic characteristics that favor more humid conditions (Fig. 2).

Fig. 2
A map of the Chilean Patagonia with 3 regions marked. Magallanes and Aysen are on the southern and northern parts. The Patagonian steppe is to the eastern end of the former.

Area and location of the steppes in Chilean Patagonia. Source Own elaboration, based on Pisano [56], Moore [51], Pliscoff & Fuentes-Castillo [59]. The approximation was generated from photo interpretation using high-resolution imagery sources available from Google satellite, Bing and Yandex satellite, and auxiliary data from the ASTER GDEM Digital Elevation Model

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The area occupied by steppe is marginal in the Aysén Region (108,490 km2; [31], with an approximate area of 2,562 km2 (2.36%, Table 2). The steppe in Aysén is concentrated on the border with Argentina, with some valleys that intrude to the west where they form an ecotone between the open steppe and the forest and mountain areas of the Andes [58]. The steppe valleys that enter from Argentina into Chile are found in Alto Río Cisnes, Coyhaique Alto, Balmaceda, the areas adjacent to the General Carrera and Cochrane lakes and the Chacabuco River valley [67]. The commune of Coyhaique has the highest representation of steppe in this region (Table 2).

Table 2 Patagonian steppe distribution according to political-administrative divisions
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The Magallanes Region (1,382,033 km2) is subdivided into two sectors, one continental, including archipelagos and channels (132,033 km2) and the other Antarctic (1,250,000 km2) [18]. The region presents a much wider steppe distribution than Aysén, covering an estimated area of 24,434 km2 (18.5% of the region’s continental area, Table 2), which is physiognomically similar to the Argentine steppe, which it is a continuum of [67].

The steppe is also distributed on the eastern slope of the Andes, in Puerto Natales, and on both sides of the easternmost portion of the Strait of Magellan, close to the Atlantic Ocean, reaching a large area in the northern part of the island of Tierra del Fuego [58, 67]. 91.55% of the steppe area of Chilean Patagonia is located in the provinces of Tierra del Fuego and Magallanes (47.70% and 43.85%, respectively), while only 8.45% is in the province of Última Esperanza (Table 2). This province is a steppe zone with spatial and topographic patterns more similar to the steppe of the Aysén Region. The elevation gradient is similar to that of the Aysén Region.

The altitudinal gradient decreases from north to south; the Aysén steppe has average altitudes of over 400 m above sea level (m), while the southernmost portions, located in the Magallanes Region, have average altitudes of less than 200 m. (Fig. 3). Changes in vegetation occur as a result of this elevation gradient, which generates an altitudinal variant of the Chilean Patagonian steppe that includes high, semi-arid, and non-forested territories with more or less dense herbaceous vegetation [46, 57].

Fig. 3
A box plot with error bars of the distribution of the Patagonian steppe by elevation and 8 zones. Zones 1 to 8 have declining elevation from 970 to negative 100 meters above sea level. Values are approximated.

Source Own elaboration; elevations were calculated from 7.5 M of data from the ASTER GDEM digital elevation model

Distribution of the Patagonian steppe according to zones. Zones 1 to 5 correspond to the Aysén Region and zones 6 to 8 correspond to the Magallanes Region. The box plot illustrates the elevational variation of steppe zones in Chilean Patagonia. The lines inside the boxes indicate the medians, while the boxes represent the 1st and 3rd quartiles. The lines above and below the boxes are the extreme values.

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3.2 Climate of the Patagonian Steppe

The Patagonian steppe of Chile, unlike other cold steppes, maintains more stable climatic conditions between summer and winter seasons [85]. The colder steppe climate in Chilean Patagonia also has a more pronounced thermal amplitude and relatively low rainfall, with higher annual amounts at its western boundary, decreasing to the east and north, reaching 200 mm yr−1 [11], the potential evapotranspiration fluctuates between 470 and 680 mm yr−1, depending on the area of the region and the year [61]. Winters are shorter and summers are rather cold compared to the steppes of Central Asia or North America [85].

The Andes Range forms a barrier that stops the air masses coming from the Pacific Ocean in its Patagonian and Fuegian sections, and is responsible for local climatic modifications [24]. In the Aysén Region the Andes Range is in the east,the steppe is found in areas of lower altitude in the east that appear as intrusions from Argentina. There are four main areas, separated by elevated platforms: Alto Río Cisnes, Ñirehuao, Coyhaique Alto, and Balmaceda. All of these are depositional planes bordered by gentle hills (Regional Secretariat of Planning and Coordination, [73]. The Andes Range is on the western edge of the Magallanes Region, almost facing the Pacific Ocean, approximately north–south in its northern part, twisting its course to a northwest-southeast direction in its southern part [11] the steppe is located at the eastern end. There is a strong predominance of winds from the western quadrant (westerlies) [50], which upon reaching the American continent at its southern end are modified locally by the geomorphology, altitude and distance from the sea, giving rise to an enormous variety of climates in the Magallanes Region [24].

The climatic conditions have a longitudinal gradient in the steppe of the Aysén Region; the climate is more arid than in the western strip, receiving strong influence from the dominant bioclimates in the east. It also has some continental tendency, with greater annual thermal amplitude, along with a progressive decrease in precipitation and relative humidity [22, 46]. In the Magallanes Region the climatology is determined by various atmospheric factors of general circulation, such as the position of the Pacific anticyclone and the Humboldt Current [11]. These atmospheric factors are associated with a strong zonal component of winds from the west and the proximity of the Antarctic continent, with frequent displacement of the polar front towards mid-latitudes [11]. Therefore, several factors interact to define a main climate type for the Magellanic steppe.

There is a very marked Foëhn effect, which occurs when moisture-laden air masses precipitate on the western slope of the Andes (windward), while precipitation drops sharply on the eastern edge (leeward) [11]. This happens because of the strong adiabatic gradient that causes the temperature of the air mass to be lower on the western edge and higher on the eastern edge [11]. This is the main effect responsible for the uneven distribution of precipitation in Patagonia, both in Aysén [31] and Magallanes [11].

Precipitation occurs throughout the year in the steppe zone of Aysén, with an approximate annual average between 444 mm yr−1 [58] and 588 mm yr−1 [31] and a range of 11–70 mm between the driest and wettest months, respectively, so there would not be marked seasonality [58], Fig. 4). However, precipitation is somewhat lower in the Magallanes Region, approximately 328 mm yr−1, with a range of 16–39 mm [58], Fig. 4). Although scarce, precipitation is more evenly distributed over the seasons [56]. In both regions, much of the precipitation occurs as snow in the winter months (June–August, [58]), although in the Magallanes Region the annual snow cover is variable [83].

Fig. 4
2 maps of the precipitation isohyets and isotherms for the Aysen, Magallanes, and Patagonian Steppe. 1. It increases westward from 300 to 5000. 2. Mean annual temperature decreases westward from 7 to 3 degrees Celsius.

Source modified from Fick and Hijmans [25]

Precipitation isohyets (mm-yr−1) and isotherms (annual mean °C) for the Aysén and Magallanes regions.

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Average annual temperatures in the steppe zone in Aysén are less than 6.5 °C [31, 58], with ranges between 2.2 °C (average annual minimum) and 11.6 °C (average annual maximum) [31], while in the steppe zone of Magallanes the average is 4.7 °C with a range of 0–9.2 °C [58]. Average temperatures in inland areas of Magallanes in the winter months do not exceed 0 °C and extremes can reach −25° to −30 °C [11]. In summer the extreme night temperatures reach −11 °C, and can reach 30 °C during the day [11].

The following climatic groups have been defined for the steppe zone in the Aysén and Magallanes Regions according to the Köppen-Geiger classification, which considers ranges of precipitation and temperature [44]: (i) boreal Andean climate (Cfc) (Aysén [31, 44]), (ii) trans-Andean climate with steppe degeneration (Dfk) (Aysén—[57], Magallanes—[57]), (iii) cold steppe climate (BSk), the dominant climate in the Aysén steppe and in the extensive area of eastern Magallanes and Tierra del Fuego [31, 44, 57]. The climate stations most representative of the cold steppe climate in the Aysén and Magallanes Regions are indicated in Table 3. In both regions, precipitation is within the range of 200 to 400 mm yr−1 (Magallanes) and between 327 and 588 mm yr−1(Aysén).

Table 3 Mean precipitation (mm yr−1) of different localities of the Aysén and Magallanes regions (Mag) in the Patagonian steppe zone, indicating the number of years with records
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A photo of a Guanaco and a sheep grazing in a dry steppe.

Guanaco and sheep grazing in steppe dominated by coironales. Mount Aymond sector, Magallanes and Chilean Antarctica Region. Photograph by Paulo Corti

3.3 Soils in the Patagonian Steppe

Most of the soils of the Fuegian-Patagonian area have developed on moraine systems of the second and third glaciation or on mixed moraine sediments of the same epochs [56]. Both types of soils contain abundant ash from Pleistocene-Quaternary volcanism mixed with fluvial and/or colluvial sand and silt [56]. A flat or slightly undulating landscape predominates, dominated by sedimentary plateaus from the Tertiary period without a well-defined drainage towards the sea,rainfall is channelled into temporary lagoons or large internal lowlands [5].

Soils in the steppe of the Aysén Region have formed in topographic positions that vary from alluvial terraces to undulating hills with volcanic ash-generating materials on glacial and fluvioglacial deposits [31]. The aridity of the eastern plains of the Magallanes Region conditions the type of vegetation and soil development [56], from semi-arid, more weathered, less leached and less acidic, to those located further west, with a shallow surface horizon [56]. These soils have an upper layer of fine sand with organic matter [5]. Textures change to clay loam in depth,they are stony throughout the profile, with a pH ranging from slightly acidic to moderately alkaline [5]. The coironales in this area have an average soil bulk density of 0.71 g cm−3, ranging from 0.58 to 0.87 g cm−3 [62], and low nitrogen content [68].

There are mollisol and inceptisol soils in the small valleys inserted in semi-arid and xerophytic scrubland areas that occupy the steppe in the eastern part of the Aysén Region [31], according to the soil classification of the United States Department of Agriculture (USDA). Mollisols and aridisols predominate in the Magallanes steppe 5. Mollisols, also called chernozems and kastanozems (or brown soils) according to the soil classification of the Food and Agriculture Organization of the United Nations (FAO), are formed under grassland vegetation in climates with moderate to marked water deficit [47] and have a horizon with concentrations of secondary carbonates,calcium is the dominant cation in the surface horizons [47]. These soils appear with increasing precipitation (ca. 300 mm) in well-drained areas [56]. Aridisols do not have water available when the temperature is suitable for the growth of plant species [47], while inceptisols are incipient with slight morphological development in the subsoil, including structure formation or brownish color [31].

Table 4 Macronutrients and general characteristics of soil grou**s in the steppe zone of the Aysén Region, compared to chestnut soils, grasslands, meadows, meadows and murtillares in the steppe zone of the Magallanes Region
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There are mosaics of other types of soils with azonal characteristics in the steppes [29], generated by humid depressions, and hydromorphic soils of the mallín type, which present considerable accumulations of incompletely humidified organic matter that forms saturated humus in soils with little differentiation between horizons [58], where acidity tends to decrease with depth [79]. According to FAO soil taxonomy, these humid depressions or vegas are classified as histosols and fluvisols,there is considerable variability in their organic matter content and pH, tending to salinize in arid conditions [79]. They have a soil bulk density of 0.28 g cm−3, with a range of 0.20–0.39 g cm−3 [62].

The vegas are the soils with the highest fertility within the Patagonian steppe [68]. These humid depressions have been classified into five types for the Magallanes Region, where it is indicated that the soils of non-saline vegas have low phosphorus (P) availability and low retention capacity,but they have high content of calcium bases (Ca), magnesium (Mg), potassium (K), sulfur (S), and micronutrients (Table 4).

Steppe (chestnut) soils have P values as low as 5 mg kg−1, 6.0 mg kg−1 for the d deedle-Dee (in Spanish murtilla) or heath community and reaching 16 mg kg−1 in the more alkaline grasslands (Table 4); they possess an average phosphorus buffering capacity of 13.6 kg P ppm−1 Olsen [31]. They have high K and Mg content, reaching values of 512 mg kg−1 and 4.2 meq 100 g−1 dry soil respectively, but with the lowest values for both nutrients in the murtilla or heathland community (Table 4). S availability is 1.6 and 4.0 mg kg−1 for the steppe soils of the Aysén Region and the drier sectors of Magallanes, respectively (Table 4). The soils under the vegetation community of vegas have S values higher than 12 mg kg−1, a threshold figure [66], since an agronomic response to grassland fertilization above this value is not expected. S availability is 6.8 mg kg−1 for the murtilla or heathland community, which is considered low.

Although steppe soils respond to fertilization with N, P, and S, increasing the productivity of the grassland, annual production would remain low due to the arid conditions in which the naturalized grassland is found. Therefore the application of fertilizers to increase pasture productivity is not profitable [68]. The exception would be the vega communities, which stand out for their higher levels of nutrients and moisture compared to soils under other plant communities such as coironales and murtillares [79].

The pH tends to be slightly acidic to alkaline in most of the steppe soils, with values ranging from 5.7 to 7.7 (Table 4). The pH values of the soils under the main steppe plant communities range from 4.8 - 6.2 for the murtilla and coironal communities, respectively (Table 4). The murtilla (Empetrum rubrum) community has this pH because this species has the ability to lower soil pH [15], Borelli and Oliva, 5. The average values of aluminum (Al) saturation are lower than 6.2% (Table 4), which according to Rodríguez [66] is considered low, the exception is the murtilla community, which has 55% saturation.

The highest extractable Al value found was 171 mg kg−1 (Table 4), which has no effect on phosphorus retention, since a value lower than 400 mg kg−1 is considered very low [66]. Once again, the exception is the murtilla community, which has 748 mg kg−1.

3.4 Predominant Vegetation of the Patagonian Steppe

The representative vegetation of the Patagonian steppe is a community of graminoids and hard herbs, without the presence of trees [58]. Gajardo [27] and Luebert and Pliscoff [46] suggested that the steppes in Aysén and Magallanes belong to two distinct sub-regions, differentiated mainly by the greater presence of the shrub component in Aysén and by the dominance of different species of coirones. The steppe in the Aysén Region is primarily associated with coiron grasslands, similar to those found in the provinces of Magallanes and Tierra del Fuego, but covering a significantly smaller area [31], and with the difference that they are mainly dominated by Festuca pallescens [57] and Stipa (Stipa spp.) [31]. Coironales in the steppe of the Magallanes Region occupy approximately 24% of the total area destined for livestock use [74], including several plant communities with variable physiognomy, from the typical hard grass steppe of F. gracillima (Fig. 5) to shrub steppe and shrublands, and also includes vegas or hygromorphic cespitose communities [56]. The climatic differences between the steppe of the Aysén Region and that of Magallanes would be the main cause of the floristic differences [58].

Fig. 5
A photo presents the long shot of a dry grassland. It has a fence running across it.

Coiron grasslands (Festuca spp.) in the steppe of Tierra del Fuego

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The steppe of the Aysén Region is characterized by the white or sweet coirón (Festuca pallescens), which forms robust plants with a strong and deep root system; it is accompanied by other perennial grasses of the genera Festuca, Agrostis, Stipa, Poa, Bromus, and Deschampsia that grow in aggregate form as tussock [32]. Other xerophytic shrubs common in the Aysén steppe are the green bush (Nardophyllum obtusifolium), different species of yareta (Azorella spp.), and senecio (Senecio sp.), fachine (Chiliotrichum diffusum), neneo (Mulinum spinosum), white hawthorn (Discaria chacaye), and christmas bush (Baccharis magellanica) [76]. The proportion of endemic species in the dominant families is very high, with up to 60% endemism in Leguminosae and 33% in Compositae [20]. Other outstanding elements are the wide diversity of lichen and herb species with showy flowers, such as the Chilean oxalis (Oxalis adenophylla), the Darwin’s slipper (Calceolaria uniflora), and a variety of orchids such as the porcelain orchid (Chloraea magellanica) and the peatland orchid (C. chica) [76].

The drier Magellanic steppe has an extensive coiron grassland, which contributes 30–70% of the total cover [5]. The spaces between coirones and shrubs are occupied by a large group of small native grasses, mainly perennials with rhizomes and stolons, dicotyledons, and naturalized species that are a key contribution to the diversity and pastoral value of this community, which is preferred by sheep to the detriment of coiron [13, 74]. There are also native herbaceous plants, mainly annuals [27]. This combination produces a plant formation that develops with variable vigor depending on the characteristics of the site [74], especially water availability [2, 58, 74] (Fig. 6).

Fig. 6
A photo of a steppe. It has a hill with 3 types of plant species in 3 regions, labeled, a, b, and c. a. The left-half of the steppe with Murtilla and Balsalm-bog. b. The right half with fachine bush. c. At the foot of the hill where reeds dominate.

Community of plant species distributed according to exposure and water availability in the steppe of Tierra del Fuego: a area with greater exposure to the wind where murtilla or diddle-dee (Empetrum rubrum) and balsam-bog (Bolax gummifera) predominate; b area that is protected from the wind and with greater accumulation of water in the soil, where the fachine bush (Chiliotrichium diffusum) predominates; c area at the base of the hill, where there is a greater accumulation of water compared to the other communities, is dominated by reeds (Marsippospermum grandiflorum)

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Fig. 7
3 vegetation profiles plot elevation versus distance and precipitation for 3 regions and 9 plant species. In Ultima Esperanza and Magallanes, Murtilla and Nirre grow at top elevation. In Tierra del Fuego, Nirre grows at top elevation. Precipitation drops eastward and rises southward, in order.

Source: own elaboration, based on the ASTER GDEM model and [25]. [Coirón: Festuca gracillima; Calafate: Berberis microphylla; Murtilla: Empetrum rubrum; Mata barrosa: Mulinum spinosus; Pasto ovillo: Dactylis glomerata; Rocas: rocks; Ñirre: Nothofagus antarctica; Lenga: Nothofagus pumilio; Coihue: Nothofagus betuloides]

Vegetation profile of three transects in the provinces of: a Última Esperanza, b Magallanes, c Tierra del Fuego. The elevation, precipitation (mm yr−1), and main components of vegetation within the transect are indicated. The transects are shown with a black line in region maps.

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Three main plant communities can be distinguished in the steppe of the Magallanes Region, according to the edaphic conditions [51, 58], topography [51], drainage, wind exposure [58] and microclimate of the sites [51]. Frequently there is a combination of these communities (Fig. 7, [51, 57]: (a) Natural grasslands: represented mainly by three types: (i) coirón grasslands (Festuca gracillima and F. magellanica) accompanied by other grasses and herbaceous species [51] which have local hygrophytic, mesophytic and xerophytic expressions [58], (ii) mesic grasslands, which are the most humid within this plant community [51] and are composed of meadows and hygrophytic grasslands [58], (iii) salt meadows, with azonal vegetation that develops in inland depressions or marine coasts [29] where evaporation exceeds water flow, accumulating salts [51]. The coironales are found mainly in the great plains of the northern sector of the provinces of Magallanes [58] and Tierra del Fuego [51], while the meadows are generated by specific conditions in depressed sectors of the site [51, 58], which are concentrators of surface runoff [58]. (b) Shrubs: represented mainly by fachine [51, 58] and other species of more restricted distribution such as the green bush, black bush (Mulguraea tridens), paramela (Adesmia boronioides) [58], mata barrosa (Mulinum spinosum) [78, 80] and barberry (Berberis microphylla) [51, 56]. Fachine appears in the most humid sectors of the Patagonian steppe [58], with a dispersion in the region above 350 mm yr−1, where the coirón gradually gives way to this shrub community [51] (c) Subshrubs and/or heaths: mainly composed of murtilla or diddle-dee (Empetrum rubrum) [51, 58], accompanied by other cree** shrub species such as christmas bush Baccharis magellanica [51, 78], dwarf barberry (Berberis empetrifolia) [56, 78] and species that form cushions, tufted azorella (Azorella caespitosa), nardófilo (Nardophyllum bryoides) [51, 78], balsam-bog (Bolax gummifera) [78, 80] and yaretilla (Azorella trifurcata) [56, 78]. Murtilla is generally found on flat, very exposed terraces, with stony, nutrient-poor [5], thin [51], coarse-textured, acidic soils [15].

3.5 Fauna in the Patagonian Steppe

The fauna that currently inhabit the Patagonian steppe come mainly from species that persisted during the cold periods of the Pleistocene (ca. 2.6 million years BP) and that managed to survive the harsh climate conditions [35]. Paleontological evidence indicates that animal species that survived in periglacial areas expanded rapidly once favorable warmer environments were established in more recent times [35]. Thus the fauna of the Patagonian steppe in Chile derives from colonization in an east–west direction as the ice retreated.

In contrast to the steppes of the Northern Hemisphere, where there is a great diversity of animal species, the Patagonian steppe has a rather reduced faunal diversity, but with important endemisms [67]. Mammals inhabiting the Patagonian steppe are represented by seven orders, 17 families and at least 14 genera [42]. Few large mammals are found, with the exception of the guanaco (Lama guanicoe), a camelid widely distributed in the steppe in both Aysén and Magallanes.

Most are herbivorous mammals, rodents of the subfamily Sigmodontinae such as the Edwards's long-clawed mouse (Notiomys edwardsii), and the family Ctenomyidae, such as the Magellanic tuco tuco (Ctenomys magellanicus) [42], and in Coyhaique Ctenomys coyhaiquensis [76], or of medium size, such as Chinchillidae (e.g. Wolffsohn's viscacha, Lagidium wolffsohni, [42]. These last two families have species with fossorial habits,others form colonies [42], all are groups endemic to South America. Two of the small- and medium-sized species belong to the family Dasypodidae or armadillos: the dwarf armadillo (Zaedyus pichiy) and the larger hairy armadillo (Chaetophractus villosus) [42].

There are two canids among the carnivores of the Chilean Patagonian steppe: the culpeo (Lycalopex culpaeus) and grey (L. griseus) foxes; the former is larger [42]. There are also three species of felids: the Geoffroy’s cat (Leopardus geoffroyi), the pampas cat (L. colocolo), and the puma (Puma concolor),the last is the largest carnivore in the steppe [42]. There are also smaller carnivores of the family Mustelidae, the Patagonian skunk (Conepatus humboldtii), the lesser grison (Galictis cuja) and the Patagonian ferret (Lyncodon patagonicus) [42].

Introduced mammal species are also found, which have a negative impact on the steppe ecosystem due to predation and grazing on native species [40, 50]. One carnivorous mustelid, the American mink (Neovison vison), is found in both Aysén and Magallanes [40]. Two rodents, the muskrat (Ondatra zibethicus) and the American beaver (Castor canadensis), are present only in Magallanes [40]. Two lagomorphs, the rabbit (Oryctolagus cuniculus) and the European hare (Lepus europaeus) are present in both regions, and two ungulates, the red deer (Cervus elaphus) and the wild boar (Sus scrofa), still only present in Aysén, although there is a red deer farm on the island of Tierra del Fuego [40]. There are also feral domestic species such as cattle and horses, as well as cats and dogs, which roam near urban areas, degrading the ecosystem and affecting native bird and mammal species [40, 42].

Birds are represented in the Chilean Patagonian steppe by several orders. Among the most visible are those that group together flightless birds, the Rheiformes, represented by the Darwin’s rhea (Rhea pennata) and others with limited flight, and the Tinamiformes with the elegant crested tinamou (Eudromia elegans), adapted to open and arid environments [84]. The large flying carrion-eating Andean condor (Vultur gryphus) is a member of the order Cathartiforme, birds of prey include the orders Accipitriforme, with the black-chested eagle (Geranoaetus melanoleucus) and the variable hawk (G. polyosoma), and the Falconiformes, with the crested caracara (Caracara plancus) and the aplomado falcon (Falco femoralis) [84]. Water birds of the order Anseriformes include the black-necked swan (Cygnus melan-coryphus), the coscoroba swan (Coscoroba coscoroba), the upland goose (Chloephaga picta), the red shoveler (Spatula platalea) and the spectacled ducks (Speculanas specularis), and the wigeon (Lophonetta specularioi des),the order Phoenicopteriforme is represented by the Chilean flamingo (Phoenicopterus chilensis). These use permanent bodies of water or small temporary lagoons in the steppe, which are highly productive in plant matter [84]. Several smaller birds belonging to the order Passeriformes and seabirds of the order Charadriiformes use the steppe as a nesting and feeding ground [84].

The herpetofauna is mainly represented by lizards of the genus Liolaemus, with the Magellan's tree iguana (L. magellanicus; [8]), a and few amphibians [17]. The latter are the Patagonian toad (Nannophryne variegata), the portezuelofrog (Atelognathus salai) and the large four-eyed toad (Pleurodema bufonina), which tolerate the limited humidity conditions of the steppe [17].

3.6 Ecosystem Services of the Chilean Patagonian Steppe

Ecosystem services are biophysical processes that generate resources, functions, or goods that are useful for human well-being [30, 39]. Ecosystem services acquire different values depending on the type of stakeholder and the rate of ecosystem provision [69]. Some human groups focus their activity on livestock production, others on water quality and access for people and animals [69], nutrient cycling, cultural services and climate regulation, or pollination functions [30]. There has also been increasing interest in protected areas that ensure the viability of biodiversity and its ecological processes and benefits. However, the demand for ecosystem services depends on the level of education, income, values, culture and geographic location of the human groups that use them [69].

Steppe ecosystem services support over one billion people globally [30]. If we consider the benefits provided by steppe ecosystems for diverse human groups [69], including native peoples, the value of the Patagonian steppe in Chile is clearly underestimated and focused in relation to one of the main economic activities, extensive sheep and cattle ranching [49]. This steppe cattle ranching began in Magallanes over 130 years ago [49] and about 100 years ago in Aysén [70], and continues to this day. An important ecosystem service of the steppe is the capacity of soil organic matter to sequester significant volumes of carbon [43]. The movement of carbon from the atmosphere to the soil and vegetation, where it is stored, is called carbon sequestration, and is an important ecosystem contribution to global climate change mitigation through fixation via photosynthesis [10, 50]. The type of grazing management of steppe grasslands directly influences carbon accumulation. Intensive grazing (Fig. 8) and grazing exclusion are the management types that reduce the amount of carbon sequestered and lead to lower species richness in plant biomass, compared to moderate grazing [69]. These results could vary in the steppe, depending on soil type, vegetation and climate [10].

Fig. 8
A photo of a large grassland with a vertical fence separating it into 2 areas. Area on the right, labeled, a, has short and scarce grass growth while that on the right is labeled, b, has dense growth.

Example of forage and biomass production depending on the type of grazing. a area with intensive grazing; b area with moderate grazing

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The type of management to which the steppe is subjected, especially when it involves production, can affect the supply of other ecosystem services such as the quality and quantity of available water, the conservation of biodiversity of plant and animal species, and carbon sequestration [69]. Therefore, it is important to promote policies that provide incentives and benefits that support conservation and recognize the value of the multiple ecosystem services provided by steppes, and thus ensure management that facilitates their resilience and sustainability [30]. Resilience-based management generates the greatest ecosystem sustainability (Fig. 9), as it recognizes the inevitability of change and seeks to channel it to maximize multiple ecosystem services [9]. This type of management implies that the natural resource used is developed in such a way as to allow its recovery to the initial state prior to intervention. An example of this type of management is grazing with stocking rate adjusted to the production of the site, which allows the steppe vegetation to recover within its annual cycle.

Fig. 9
A line graph of ecosystem sustainability versus time from human settlement. Pre-industrial use of the resource rises concave up as time progresses with 4 points, including exploitation, management that does not produce a change in state, ecosystem management, and resilience-based management.

Source modified from Briske [9]

Progression of resource management in natural ecosystems since the first human settlements.

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3.7 Conservation and Threats

There are several threats to the conservation of the Patagonian steppe; the most relevant ones related to anthropogenic impacts are mining [38] and the oil industry [29], which generate significant negative effects [29, 38]. The area of hydrocarbon exploitation in the Magallanes Region coincides with the steppe ecosystem [37]. Overgrazing of grasslands by livestock leads to aridization [26] and allows the invasion of exotic species of plants and animals [7, 40]. Tourism [37, 38], despite being an activity with sustainable development purposes, has generated changes that increase pressures on the territory, with a tendency towards intensive exploitation that could be detrimental to steppe systems [37]. Added to these threats are the fires that are frequent in this ecosystem [55, 81, 82] and the change in climate conditions due to global change, which will produce warmer winters, with precipitation mostly in the form of rain instead of snow [50, 85].

Because it is considered an ecosystem of agricultural importance [58], the representation of the steppe in the National System of Protected Areas (in Spanish SNASPE) is low in the regions of Aysén and Magallanes [59, 60]. It is worth mentioning that these two regions have 69% of the total area of SNASPE in Chile [16]. There are few state protected areas that have total or partial coverage of steppe surface within their boundaries. The Patagonia National Park is located in the Aysén Region (421 km2), Torres del Paine National Park (401.9 km2) and Pali Aike National Park (44.2 km2) are in the Magallanes Region. Only Pali Aike National Park has exclusive protection of steppe environments, since in the other areas only small portions of isolated steppes are protected within a matrix mainly composed of deciduous forests in mountainous areas. The total area of Patagonian steppe in southern Chile is approximately 26,996.9 km2,the percentage of steppe under some form of state protection is only 3.2% of the total [60]. A similar situation occurs in the Argentine steppe, where only 0.6% of its area is protected [29].

Fires are one of the most aggressive and sudden disturbances that can affect native ecosystems, strongly depleting and modifying their cover, structure and composition [55], as well as reducing carbon and nutrient storage. The more severe the calcination of biomass and organic soil, the more severe the impact on the ecosystem's resilience, i.e. its ability to return to the state prior to the disturbance. Fires in the Patagonian steppe have had different degrees of severity, causing a decrease in the cover of all functional groups of vegetation and an increase in exotic species in sectors where the fire reached greater severity [28]. However, fire regimes have changed in response to climate variability, vegetation type and changes in land use,therefore, they are expected to continue to change during the twenty-first century, increasing fire frequency as a consequence of climate change [50] and increasing anthropogenic impact [52].

In the ecotone, i.e. the transition zone of the Patagonian steppe with the deciduous forests of lenga (Nothofagus pumilio) and ñirre (N. antarctica) present in Aysen Region in just a few decades the development of livestock pastures has produced a mosaic-type anthropized landscape, in which large tracts of semi-natural grasslands are found with scattered remnant fragments of native forests that still persist [32, 70]. It is here that intentional fires have been an important disturbance, which together with extensive livestock activity, explain the biodiversity and ecological functioning of these ecosystems [71].

An example of the effect of fires can be seen in Torres del Paine National Park, where they have affected nearly 47,000 hectares over the last 30 years. These events have damaged pre-Andean scrubland, steppe, and forest ecosystems [81], This park has been affected by 57 fires of varying sizes since 1980, which have impacted its ecosystems [55]. The Olguín fire (in 2011) was the most extensive and devastating, burning about 7% of the park's surface, of which 59.7% was Patagonian steppe, 28.6% scrub or shrub steppe, 9.7% native forest, and 1.9% other vegetation [55].

Another alteration of the original landscape of the Patagonian steppe is agricultural and livestock production, which has altered the floristic composition and original plant productivity of its communities [58]. In the Magellanic steppes sheep grazing and high stocking rates without monitoring have transformed many grass communities into degraded grasslands [15]. Pasture management by intensive grazing or the exclusion of grazing generate the greatest decrease in species richness [69]. Maintaining soil cover is a vitally important issue in steppe grasslands in order to avoid soil erosion, grassland degradation, loss of primary and secondary productivity, and biodiversity [13].

The invasion of exotic plant species is another frequent threat in Chilean Patagonia [7]. One of the plant species of exotic origin that has had the greatest impact on the steppe ecosystem of the Magallanes Region is mouse-ear hawkweed (Hieracium pilosella, [63]). The mouse-ear hawkweed can colonize bare soil in degraded grasslands,once its established, the species spreads more by stolons than seed production, which is an effective strategy to occupy space before resident plant species [63]. Between 2004–2018 this species invaded 52% of the area of a property [65] at a rate of 63 ± 15 ha yr−1.

4 Recommendations

The following are recommendations for biodiversity conservation, ecosystem processes, and sustainable management of Chilean Patagonian grasslands:

  • Given the heterogeneity of the steppe system and the various intensities of management and impacts, development of a monitoring plan using satellite images and remote sensing techniques is advisable in order to determine quantitatively the spatio-temporal trends in the different types of steppe that occur in the environments of Chilean Patagonia (Fig. 2). For example, coironales dominated by perennial grasses (Festuca spp.), areas with shrub cover and more humid areas such as meadows. In addition, a monitoring plan of water availability, temperature changes, and soil fertility, the main site conditions that regulate the dominance of one plant community over another, is recommended in order to prevent or mitigate degradation processes in steppe areas subject to intensive livestock grazing or affected by fires.

  • Degraded pastures can be improved through the application of amendments that add deficient nutrients, such as nitrogen, phosphorus, and sulphur. In addition, in the specific case of Azonal soils such as the meadows (in spanish vegas) if the conditions of greater water availability and cover are maintained, these would be areas of greater resilience to climate change. Thus it is recommended that their management be differentiated from the rest of the steppe plant communities, so that their characteristics are maintained over time.

  • It is necessary to implement a comprehensive management plan that considers all possible threats to Patagonian steppe biodiversity and that takes into account the possible adverse effects of localized mineral and hydrocarbon extraction that degrade and erode these environments. Other threats to the steppe ecosystem that must be prevented or mitigated include the introduction of exotic animal and plant species that cause damage, which have been poorly assessed (mainly mouse-ear hawkweed, beaver, mink, and lagomorph species), the serious impact of fires, especially in areas of climatic transition with native forest, unregulated tourism, and agricultural activity that does not consider sustainable planning in terms of animal load and impacts. The conservation of the Chilean Patagonian steppe depends both on the protection of the ecosystem in state parks or reserves, which cover only a small portion of the steppe [60], and on the implementation of management plans and management of disturbances such as fires and exotic species in the extensive unprotected area.

  • The possibility of increasing the value of conserved steppe through the market using carbon credits captured in the Patagonian soil and vegetation should be studied. In Chilean Patagonia this is an undervalued ecosystem service, which is applied in other similar grasslands around the world, and is a consensus tool that could contribute to the conservation of the steppes and their biodiversity. To this end, it is necessary to prioritize forms of management that maximize carbon sequestration in the soil and vegetation (see Fig. 8).

  • There is a need to improve scientific knowledge on the management and impact of the abundant exotic species of animals and plants introduced in the Chilean Patagonian steppe. This objective requires integrated management with Argentine authorities in the border areas, since most of these invasive species are found in both countries and have migrated spontaneously from one country to the other. It is necessary to develop concrete plans to reduce the environmental and productive damage caused by these species. It is urgent to prevent the introduction of new alien species for any purpose, since due to limited knowledge, the Patagonian steppe for both countries has been used as an experimental ground because of its scarce population and the undervaluation of its ecosystem services. Accordingly, greater valuation and knowledge of the steppe ecosystem and its resources is essential to establish control or mitigation measures prior to the introduction of a species for economic purposes, especially in areas subject to use by the local community. Management based on ecosystem resilience should consider the ecological-social component in an integral manner, with the participation of the main regional stakeholders in the design and evaluation of management actions, which could reduce the degradation of steppes and enable their sustainable use.