Keywords

1 Introduction

The interface between the land and the oceans, i.e. the narrow band at the continental margins of the planet, is subject to strong anthropogenic pressures, including high concentration of inhabitants in certain regions, the high impact of coastal recreation and tourism, and extractive exploitation of coastal and marine resources [30]. Therefore, coastlines are key scenarios for understanding the impacts of global change [17]. One of these key scenarios is the edge of South American exposed to the Pacific Ocean between Reloncaví Sound and the Diego Ramírez Islands (41° 42′ S 73° 02′ W; 56° 29′ S, 68° 44′ W), i.e. Chilean (western) Patagonia. In contrast to the temperate and subpolar latitudes of the Northern Hemisphere, the Patagonian archipelagos, fjords and channels have remained free of large-scale human impact until recent times [77].

The continental margin of the archipelagic region of Chilean Patagonia was shaped by glacial advances and retreats during the Pleistocene [96]. This has produced a zone of steep coastal fjords and inland seas with deep bottoms generated by glacial erosion, together with tectonic effects that caused the subsidence of the continental territory of the longitudinal valley south of 41° S. Flows of matter and energy are concentrated in this inland sea, and in the channels and fjords, where they reach the highest marine productivity values in the region [61]. Due to the close land-marine link in Chilean Patagonia, and the profusion of river courses, coastal ecosystem dynamics are influenced by continental ecological processes, including large tidal changes and entrainment of sediments and organic matter from rivers to the sea [61], which is especially relevant in areas of coastal marshes and wetlands.

Twenty thousand years before present (BP), during the last glacial maximum, large ice fields covered the continent between central Chiloé and Cape Horn [72, 107]. The Nothofagus deciduous forests persisted in fragments in areas close to the ice, east and west of the mountain ranges. Evergreen forests found refuge further north, in coastal areas northwest of Chiloé and the continental coast of the Los Lagos Region. At the end of the last glacial period (10–12,000 years BP), post-glacial warming made the expansion of forests possible throughout the southern territory, forming the north Patagonian forests from the south of Chiloé to the Gulf of Penas, and the Subantarctic forests between the latter and Cape Horn [9]. Although the fjord and channel system are ecologically linked to the mainland [61], conservation and management approaches have treated them separately. Here we propose to integrate the mosaic of marine-freshwater-terrestrial ecosystems into conservation policies that consider vital processes of exchange of matter and energy that occur at the marine-terrestrial interface in Chilean Patagonia.

2 Scope and Objectives

This chapter summarizes current knowledge on the biophysical connections between terrestrial, freshwater, and marine ecosystems in western Patagonia. It also proposes ways to develop integrated conservation of biological and cultural diversity in marine-freshwater-terrestrial ecosystem mosaics, evaluating the contribution of current and potential protected areas (PAs).

The specific objectives are to: (i) describe the main ecological and biophysical characteristics of the marine-terrestrial interface in the channels, fjords, and archipelagos, including their reciprocal influence on productivity; (ii) characterize the direct and indirect anthropogenic impacts on marine-terrestrial connectivity, such as sediment and nutrient fluxes, freshwater discharges, and others; (iii) identify and describe the flows associated with the marine-terrestrial interface in this region, considering the modulating effects of climate change; (iv) describe the conservation status of species that depend on the marine-terrestrial interface and coastal habitats, identifying key species for conservation planning; (v) identify the largest PAs in the marine-terrestrial interface to focus the development of conservation plans.

3 Methods

To conduct this analysis, a body of gray literature available at Chilean academic and government institutions was examined, and published scientific references were reviewed using the ISI Web of Knowledge core collectionFootnote 1 database. Publications with a focus on the ecosystems of western Patagonia were selected. Google ScholarFootnote 2 and sources available in regional institutions were also reviewed.

3.1 Study Area and Biogeographic Location

Chilean Patagonia and its island, channel, fjord, and peninsula contours add up to more than 100,000 km of coastal environments, ranging from sheltered inland areas strongly influenced by rivers and glaciers to areas exposed to waves from the Pacific and Atlantic oceans (Tecklin et al., 2021). According to Pisano [65], four orographic regions are distinguished: Archipelagic, Cordilleran, Sub-Andean Eastern, and Coastal Plains. For the terrestrial realm, the biogeographic classifications proposed for Chilean Patagonia include the Neotropical phytogeographic region and the temperate forest biome of South America [8, 58]. Rozzi et al. [77] include the ecoregions of the Valdivian temperate forests north of 47° S and the Magellanic Subpolar forests (sensu [55]) between 47° and 56° S as the Magellanic Subantarctic Ecoregion (sensu [78, 76]).

For the marine realm we follow the classification of Spalding et al. [97]. Rovira and Herreros [75] add one more ecoregion, but essentially retain the major distinctions concordant with Spalding et al. [97]. Under this scheme the archipelagic region of southwestern South America is included in the Temperate South American Kingdom or Domain, which includes the Magallanes province in the far south.

In its western portion, this province encompasses two marine ecoregions in the latitudinal range ca. 41–58° S of Chilean Patagonia [97]: (i) ecoregion 188 (Chiloense); (ii) ecoregion 187 (Channels and Fjords of southern Chile). The Chiloense ecoregion (41° 30′ S–46° 30′ S; 277,646 km2) extends from the Coronados Gulf and the Chacao Channel in the north to the Taitao Peninsula. The Channels and Fjords of Southern Chile ecoregion (46° 30′–58° S; 849,252 km2) extends from the Taitao Peninsula to the Diego Ramirez Islands and Drake Passage. The Chiloé ecoregion has an intricate network of channels, fjords, and archipelagos with 10,705 km of coastline, forming the so-called Chiloé Inland Sea between the island of Chiloé and the mainland [99]. In this labyrinth of channels there is a tidal range of up to 8 m, abundant freshwater inflows from rivers and copious rainfall (2–3 thousand mm annually). In contrast, towards the high seas there is an exposed oceanic system associated with westerlies, with a strong marine current with one branch that flows northward, generating the Humboldt Current, and another that flows southward, generating the Cape Horn Current [15, 16].

The fjord systems of the Channels and Fjords ecoregion of southern Chile include glaciers that descend from the Andes to the Pacific Ocean. The complex coastal geography includes myriad estuaries, small rivers, high cliffs, and marshes [99]. The network of fjords, bays, bays, channels, archipelagos, estuaries, gulfs, basins, inlets, and straits has very diverse topographic and oceanographic characteristics [102]. Heterogeneity at the land-sea interface is amplified by the influence exerted by the ice fields of the Darwin Range in Tierra del Fuego (running east–west) and the Andes on the continent (running north–south), especially in the vicinity of the Southern Ice Field [72].

These orographic and climatic characteristics have a great influence on the distribution and abundance of marine biota, which have multiple interconnections with terrestrial ecosystems. In the far south, the marine and terrestrial ecoregions are under the influence of the southeastern Pacific, southern, and southwestern Atlantic oceans. The main inter-oceanic connections are the Strait of Magellan, the Beagle Channel, and, to a greater extent, the Drake Passage.

The classifications used as a basis for defining terrestrial and marine ecoregions have a high degree of coincidence in their latitudinal limits. The location of the land boundary between the Valdivian (41–46° 30′ S) and Magellan Subantarctic (46° 30′–56° S) ecoregions coincides with that of the boundary between the marine ecoregions of Chiloé and the Channels and Fjords of southern Chile. This boundary, located at 46° 30′ S, is generated by the presence of the Gulf of Penas and the northern and southern Patagonian Ice Fields, which establish a biogeographic barrier for terrestrial species due to the presence of ice masses and a harsh climate that impacts a 110 km strip of coastline. The forests present a more complex structure north of this barrier, and are multistratified, and richer in species; this gulf is the southern limit of the distribution of woody Bambusaceae, Podocarpaceae and Gesneriaceae, among other taxa typical of the temperate and northern Patagonian forest [106]. South of this barrier, the greatest diversity of plant species is concentrated in bryophytes [76], in a mosaic of forest, tundra complex and high Andean ecosystems [65, 82]. In the marine area, the Gulf of Penas coincides with the division of the oceanic drift current into the Humboldt (northward) and Cape Horn (southward) ocean currents. This point also marks the confluence of the South American, Nazca, and Antarctic plates [15], where important nutrient upwelling occur.

4 Results and Discussion

4.1 Unique Characteristics of the Archipelagic Region of Chilean Patagonia

Chilean Patagonia exhibits marked contrasts with its Northern Hemisphere latitudinal counterparts [46]. We identified singularities in four areas: (i) geographic; (ii) climatic; (iii) biogeographic; (iv) physicochemical.

4.1.1 Geographic Singularities

The 40°–60° S latitudinal band has two notable characteristics. First, the land/ocean ratio is 2% versus 98%, in contrast to the 40°–60° N band where the land/ocean ratio is 54% versus 46% [77]. This difference generates an opposition between the climatic systems of the temperate and subtropical regions of the hemispheres, with oceanic influence prevailing in the Southern Hemisphere. Second, the great latitudinal extension of forest ecosystems in South America, which surpasses other Southern Hemisphere forests. Between the Taitao Peninsula (47° S) and Horn Island (56° S) the Subantarctic forests extend almost 10° further south than the forests of Stewart Island (47° S), the southernmost forests in New Zealand (see map in Rozzi et al. [77]). Therefore, the Magellanic Subantarctic ecoregion lacks a geographic equivalent at that latitude worldwide.

4.1.2 Climatic Singularities

The climate of the temperate-subantarctic terrestrial ecosystems is modulated by the vast expanse of ocean that produces little seasonal temperature fluctuation, with moderate winters and mild to warm summers. The greater amount of land in the Subarctic latitudes of the Northern Hemisphere generates winters with average temperatures below 0 °C and very warm summers. To illustrate this interhemispheric contrast, the 2009–2012 annual thermal amplitude recorded by the microclimatic station of the Chilean Network of Long-Term Socio-Ecological Research Network (LTSER-Chile) in Omora Park, in the Magellanic Subantarctic ecoregion, was 8.9 °C (Fig. 1). In contrast, the annual thermal amplitude for the same period recorded at the Bonanza Creek LTER site in the Subarctic region of Alaska was 36.6 °C; that is, four times greater than that of Omora Park. The absolute minimum temperature at Omora Park was −7.5 °C in August 2011, while at Bonanza Creek it reached −32 °C in January 2012 [85]. This marked thermal contrast underscores the bioclimatic uniqueness of the western Patagonian region and its potential effects on the conditions of seas and coastal environments (Fig. 1). These climatic contrasts become more relevant in the face of global climate change [13, 51].

Fig. 1
Two Pareto charts are titled Omora Ethnobotanical Park and Bonanza Creek. The charts plot temperature and precipitation versus month. In A, the temperature and precipitation fluctuate. In B, the temperature and precipitation peaks from June to August.

Monthly mean precipitation (bars), monthly mean temperature (orange line), absolute maximum (dashed blue line) and absolute minimum (dashed purple line) temperatures recorded at the microclimate station at Omora Ethnobotanical Park (54° 56′ S, 67° 38′ W), Red Chilena de Investigación Socio-Ecológica a Largo Plazo (in English LTSER- Chile) (top) and at the microclimate station at Bonanza Creek, Alaska (64° 42′ N, 148° 08′ W), Long Term Ecological Research Network (LTER-USA) (bottom). Period January 2009-december, 2012; modified from Rozzi et al. [85]

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4.1.3 Biogeographic Singularities

Unlike the Southern Hemisphere, the Northern Hemisphere presents biogeographic continuity through large boreal continental masses. The land connection between North America and Eurasia until the end of the last glaciation via the Bering Land Bridge facilitated the transit of plants, animals, and human settlement in recent times. North America represented a biogeographic barrier in the marine realm, that was partial or total in different geological epochs, preventing the contact of biota between the Atlantic and Pacific Oceans. Its disjunctive character and the climatic conditions of the tropical ocean were consolidated with the closure of the Isthmus of Panama [48].

In contrast, oceanic biotas in the Southern Hemisphere have been connected since Antarctica separated from South America with the formation of the Drake Passage (30–40 million years BP), creating the Antarctic Circumpolar Current (ACC) that flows from the west, connecting the Pacific, Atlantic, Indian, and Southern, and Antarctic oceans [3, 47, 86]. Thus, marine biotas have maintained genetic fluxes between the edges of South America and Antarctica [69].

Biogeographic connections between the terrestrial biotas of temperate and Subantarctic regions of the Southern Hemisphere date back more than 40 million years, when the continental masses of Australia-New Zealand and South America were connected through Antarctica [90]. An iconic example of the Gondwanic connections between New Zealand, Tasmania, and southern South America is their forest ecosystems, dominated by tree species of the genus Nothofagus [106] and its freshwater ecosystems with galaxid fish assemblages [71, 111].

These biotas have evolved in isolation on each continent during the last 30 million years, giving rise to multiple disjunct lineages of plants and animals. Species endemism of the woody plants of the temperate forest biome of South America is 80–90%, comparable only to the oceanic islands [8], whereas bryophytes reach more than 50% species endemism in Cape Horn and the Diego Ramirez Islands [31].

4.2 Biophysical Singularities and Indirect Anthropogenic Impacts

Chilean Patagonia is one of the last regions of the planet that conserves extensive areas without major anthropogenic transformations [55]. In contrast, human activity in the rest of the planet has directly modified soil cover, altered hydrological circulation, and doubled the circulation of inorganic nitrogen in ecosystems [109]. The marine and terrestrial, temperate, and Subantarctic ecosystems located south of 40° S in Chile are exceptional in the world, because they are located in one of the least transformed areas of the planet and are relatively free of pollutants of industrial origin, in addition to the limited human population [7, 77]. Atmospheric aerosols and gases derived exclusively from processes such as evaporation and emission of gases from the ocean, which occur in ocean–atmosphere contact zones far from the coast, are transported to the coasts by westerly winds from the Pacific Ocean. As a consequence, rain and fog reach the continent in most of the western Patagonian region, so the islands and fjords are essentially free of industrial pollution [35, 112].

Inorganic salts (nitrates, ammonium, and sulfates) are present at trace levels or absent in the precipitation that sustains plants in coastal ecosystems in Chilean Patagonia [35]. In contrast, the terrestrial and aquatic environments of mid- and high latitudes in the Northern Hemisphere receive several kilograms per year of anthropogenic nitrogen in the form of nitrate and ammonium (dissolved inorganic nitrogen, DIN) via the atmosphere, along with other volatile products of industrial origin (fertilizers, smokestack emissions, combustion engine emissions, etc.). These substances of indirect anthropogenic influence dissolved in rain alter microbial systems, biogeochemical processes and the productivity of the sea and land. For comparative purposes, it has been proposed that the temperate and Subantarctic terrestrial and freshwater ecosystems of Chilean Patagonia, subject to low direct and indirect human impacts, could represent a pre-industrial global “baseline” [35], which would represent the state of ecosystems before the Anthropocene [79].

Knowledge of austral ecosystems will contribute to the understanding and measurement of anthropogenic impacts on atmospheric biogeochemical cycles and the structure of terrestrial and aquatic environments since the beginning of the industrial era [10, 35, 77].

4.3 Matter and Energy Fluxes at the Land-Sea Interface

Land-sea flow in Chilean Patagonia can be linked to physical or abiotic vectors, such as wind and water, and biological vectors (e.g. birds that feed at sea and nest on land, transporting essential nutrients to riparian environments). This section examines the primary land-sea fluxes and then the converse, distinguishing their main vectors.

4.3.1 Processes that Transport Nutrients from Terrestrial and Freshwater Ecosystems to Marine Ecosystems

Within the Chiloé and Fjords and Channels Ecoregions of southern Chile, rivers are one of the largest freshwater flows, including the Puelo (approximately 600 m3s−1 discharge, H. González, personal communication), the Baker and Pascua rivers and the large river systems of the ice fields. Further south, another important freshwater input comes from surface runoff and groundwater flow fed by annual rainfall, exceeding 6 m in some sectors. High precipitation decreases drastically towards the south and east of the Fjords and Channels ecoregion. The highest annual precipitation has been recorded in the northwest of this ecoregion, on the west coast of the Wellington and Guarello islands (48°–50° S), and the lowest has been recorded in the southeast, at the eastern mouth of the Strait of Magellan [6].

Hydrological dynamics influence the flux of elements to the ocean [41, 71]. There are important intra- and inter-annual variations in freshwater flow in the Aysén fjords from numerous rivers dependent on rainfall and snowfall regimes [41]. Consequently, marine primary productivity varies with the season and the dynamics of each fjord. The vertical stratification of fjords is characterized by deep waters with higher salinity and nutrients, and a surface layer of continental origin with low nutrient content and low salinity (nitrate and orthophosphate) [32]. A representative example is the coast of the Moraleda Channel (44° S), which receives a large amount of freshwater from glacial melt throughout the year and has a low-salinity surface layer, enriched in silt but deficient in nutrients. Primary productivity in this ecosystem is low, and phytoplankton communities are dominated by diatoms. In contrast, the ecosystems located north of the Moraleda Channel receive less fine sediment from glaciers and more terrestrial input from forests and wetlands [32]. These sediments reduce the penetration of PAR (Photosynthetic Active Radiation) light and limit local primary production. For example, in the Puyuhuapi Channel Subantarctic water dominates during spring and there is little glacial influence. The phytoplankton composition is a highly productive system of colonial diatoms with high nutrient and energy requirements [32].

Glacier melting accelerated by global warming is one of the processes that can alter the state of the marine-terrestrial system in the region [72, 104]. A combined effect of low temperature and low alkalinity water resulting from increased glacial melting has been observed in some fjords of Chilean Patagonia. This increases the local acidification of the water column, a corrosive condition for calcium carbonate (CaCO3) of aquatic microorganisms [104]. Local acidification of channels and fjords could also affect marine communities of plankton and benthos near glaciers [103]. Larvae of the gastropod Concholepas concholepas and juveniles of the mytilid Perumytilus purpuratus affected by acidification, have altered rates of food intake. Therefore, for some marine mollusks acidification alters CaCO3 absorption and the formation of their calcareous shell and produces alterations in their life cycle. Higher freshwater flux due to warming also increases turbidity in the water column, reducing primary productivity [32].

In fjords bordering forest ecosystems, freshwater is associated with the flushing of the water column of organic material from rivers and coastal forests [105]. It is estimated that water from the glacial regime contributes substantial amounts of dissolved silica and a low content of nitrate and phosphate to the surface layer of the water column. Regarding particulate organic matter, terrestrial ecosystems contribute (via rivers and glacier melting areas) around 68–86% of the carbon found in fjord ecosystems. The relevance of this allochthonous source of organic matter for fjord biota is indicated by the rate of terrestrial carbon uptake by copepods, which is equivalent to 20–50% of their body weight [105]. Therefore, the terrigenous carbon contributed to the coastal ecosystem in these fjords is particularly relevant in periods of scarce available food. Consequently, coastal productivity is linked to nutrient input derived from inland ecosystems, mainly fluvial entrainment of detritus from forest ecosystems [64, 71]. Marine upwelling in circuits associated with fjords and channels supplies nutrients to diverse assemblages of primary producers, algae, and phytoplankton [49]. The maximum fluvial discharges in the study area are recorded at 42°, 46° and 50° S (Table 1).

Table 1 Fluxes from the terrestrial to the marine ecosystem and properties related to marine productivity, with emphasis on Chilean Patagonia
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Up to 50% of particulate carbon in estuaries and fjords comes from terrestrial ecosystems [92]. The main nutrient exchanges at these land-sea interfaces include fluxes of organic carbon- and nitrogen-rich sediments transported to the sea by river channels [61], as well as a large input of silica from land to sea in rivers near glacier masses. Aerosol transport, associated mainly with fog influxes from the sea to the land [112], can reach tens of kilometers into the interior of the continent. Figure 2 and Table 1 show data on element fluxes and production processes in the fjord and channel zone of southern South America.

Fig. 2
A schematic of the biogeochemical flux in the ocean-continental margin. A ship sails on a square with resource stock and primary production. River discharge, groundwater, slope creep, and sea spray enter the square with subsurface export and erosion.

Modified from Liu et al. [49]

Major biogeochemical flux of dissolved and particulate material in the ocean-continental margin interface. The sparse human population in many areas in the Subantarctic zone reduces anthropogenic contaminant exports.

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Variation in the light extinction coefficient (Kpar) through the water column is a contributing factor to the variability in chlorophyll “a” and primary productivity in the Chiloé Inland Sea (41°–43° S; [23]) and in the southernmost fjords (47°–50° S; [67]). Kpar values appear to indicate that phytoplankton primary productivity is light limited below 15 m depth, due to the large amount of sediment discharged by runoff from land [67].

The rivers that originate in the Coast Range and flow into the west coast of the island of Chiloé, a relatively unpopulated area protected by a national park, carry chemically pure water, i.e. similar to rainwater [35], with a high concentration of marine aerosols and a scarcity of compounds such as nitrogen and ammonium retained by microorganisms and growing trees. The old-growth forests in this area, rich in organic matter accumulated in the soils over decades and centuries, export organic nutrients such as carbon and dissolved organic nitrogen hydrologically. This characteristic distinguishes many temperate forests in southern South America from those in the Northern Hemisphere, which export high concentrations of ammonium and nitrate [35, 64] of anthropogenic origin that are not retained in soils [1].

Dissolved organic nitrogen (DON) is transported massively from coastal forests to rivers and marine estuaries [35], accounting for most of the nitrogen export by rivers in areas with little human impact in Chilean Patagonia (Fig. 3a). DON is also associated with dissolved organic carbon input, feeding rivers, groundwater and coastal seas. Both compounds coming from the organic soil layer of the forests reaches the coasts naturally, stimulating productivity [112]. The hydrological flux of organic matter in different states of decomposition (humus) are dominated by molecules of diverse chemical nature, which complete their decomposition in estuaries [112] in sectors far from pollution. Terrestrial organic matter transported by rivers also includes structures mobilized downstream, such as logs and leaf litter. The fate of these organic compounds and their relationship to marine productivity, especially in areas of fjords and islands without human intervention, is poorly understood. The use of isotopes indicates that an important part of the carbon and nutrients used by aquatic organisms in lakes and coastal seas derive, to a large extent, from the terrestrial environment (Rosenfeld et al., in preparation).

Fig. 3
A is a bar graph titled nitrogen concentration. N H 4 plus, 10. D O N, 170. B is a horizontal bar graph. Nitrate, Chiloe, 0. New Hampshire, 49. Maine, 60. Ammonium, Chiloe, 5. New Hampshire, 60. Maine, 50. D O N, Chiloe, 50. Ammonium, 30. D O N, 15. Values are estimated.

(Modified from Hedin et al. [35]). b Average concentration of different forms of nitrogen in fog from Chiloé Island (n = 16), in mountainous areas of New Hampshire, USA (n = 12), and in marine fog samples from the coast of Maine, USA (n = 6). Note the differences in concentration of the three forms of dissolved nitrogen (ammonium, nitrate, and DON: modified from Weathers et al. [112])

a Concentrations of the main dissolved forms of nitrogen (nitrate, ammonium and dissolved organic nitrogen, NO3, NH4 and DON) in rivers descending to the sea from watersheds covered by native forest of Chiloé National Park

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A direct contribution to the ocean from the leaves and trunks of the evergreen riparian forests of Nothofagus betuloides which grow on the rocky walls of the fjords, has been reported in the archipelagic region of Magallanes (Rosenfeld et al., in preparation). During high tides, the overhanging branches of these trees are submerged and become substrate for the establishment of mosses, various species of macroalgae, and other marine organisms. In fact, a species of marine mollusk of the genus Bankia develops in specific habitats provided by the tree trunks that fall into the sea along the coasts [113]. Another example is the marine urchin, Pseudochinus magellanicus, which in coastal areas is covered with mollusk remains, leaf litter or other detritus that protect it from incident radiation [63]. A study of 281 individuals of P. magellanicus on Navarino Island found that urchins use shells of Nacella, Mytilus, Crepipatella, leaves of N. betuloides and N. pumilio, and pieces of wood (Ojeda and Rosenfeld, personal communication). Thus marine-terrestrial interactions are not only linked to chemical cycles, but also to land-based material that provides habitats for algal and invertebrate species.

4.3.2 Nutrient Inputs from Marine Ecosystems to Terrestrial and Freshwater Ecosystems

The Chilean Patagonian coast is exposed to westerly winds that transport clouds laden with moisture, but scarce inorganic nutrients (ammonium, nitrate, and sulfates) from the surface of the Pacific Ocean [35]. Analysis of fog water shows that clouds formed over the ocean have a high proportion of DON [112], however, inorganic nitrogen concentration (ammonium plus nitrate) in rainwater and clouds is extremely low compared to those in industrialized regions of North America and Europe (Fig. 3b). Organic nitrogen concentrations in Chiloé rainwater are up to 13 times higher than those in other remote regions of the world ([112], Fig. 3b) and the concentration of inorganic nitrogen in clouds is higher than in rain. Therefore, organic and inorganic nitrogen in clouds and haze, in addition to fixation by free microorganisms, are a significant source of nutrients for terrestrial ecosystems in southern South America, which are strongly nitrogen-limited [70], and possible sources of this element of marine origin are relevant for forest ecosystems.

According to Weathers et al. [112], the organic nitrogen present in the clouds and rainwater of the Chiloé and Subantarctic regions of Magallanes originates in organic matter from terrestrial or marine organisms, gaseous emissions from marine sources, terrestrial biomass, or from fires, even in remote regions. A stoichiometric analysis of the C:N and C:P ratios of rainwater does not suggest an origin from phytoplankton or marine bacteria, or from fires or pollen present in the atmosphere [112]. Due to the direction of the winds and considering the proportion of nitrogen that reaches terrestrial ecosystems via aerosols and fog, the organic and inorganic nitrogen from rainfall in the forests of Chiloé would have an oceanic source. This contribution is biologically significant in non-industrialized areas where the concentration of nitrate and ammonium in rainfall is extremely low (Fig. 3a, [35]). Accordingly, many terrestrial ecosystems in areas far from anthropogenic pollutants are supplied, in part, by oceanic sources.

Large mammals and seabirds are important biotic vectors between marine and terrestrial ecosystems. Along the coasts of channels and fjords there are historical and recent records of large whale strandings that can mobilize nutrients from the ocean floor to coastal areas [24, 37]. In the archipelagic zone, marine mammals and birds transport large amounts of nutrients from the sea to islands and other environments. For example, bird species that form breeding colonies can modify coastal flora and environments. Globally, large mammals such as whales can transport as much as 2.8 × e7 kg y−1 from the sea to land [24].

Biotic vectors include naturalized salmon species that now inhabit channels and fjords, which due to their enormous proliferation have altered the transport of nutrients from the ocean to mainland rivers [14, 24, 56]. For example, during the mature stage, chinook salmon migrate from the ocean to spawn and die in rivers. This species does not feed in rivers, but when they die, the fish release nutrients into the freshwater ecosystems,they can also transport marine parasites into the region’s rivers [18]. Salmon farming has both a direct biotic impact and an indirect one through the social impact of the explosive development of aquaculture since the 1990s, transforming the old tradition of artisanal fishing [100].

A panoramic view of hills with lush vegetation and snow-filled mountains at a distance.

Estero Amalia, Bernardo O'Higgins National Park, Magallanes and Chilean Antarctica Region. Photograph by Nicolás Piwonka

Another biotic vector associated with human activity is the collection of macroalgae: red seaweed (Gigartina skottsbergii), black seaweed (Sarcothalia crispate), and huiro (Macrocystis pyrifera), which have been used since pre-Columbian times as agricultural fertilizer and animal feed, mobilizing nutrients from the coasts to terrestrial ecosystems. Today, innovations are being made in ways that integrate traditional and scientific knowledge to develop bio-fertilizers and alga management and cultivation practices [50]. The red seaweed harvest is concentrated in the latitudinal range of the three archipelago regions of Chilean Patagonia [50] (Fig. 4). Between 2010 and 2016, 98.5% of the seaweed biomass extracted in the country was concentrated in the three southern regions: Los Lagos (53.5%), Aysén (10.1%) and Magallanes (34.9%). The remaining 1.5% was extracted in the Bío-Bío Region (Fig. 4). The Los Lagos region concentrated artisanal black sea bass fishing activity, with 80% of the biomass harvested. Both seaweeds grow slowly and suffer a progressive decrease in their populations and biomass, and in the morphological and reproductive attributes of their fronds. It is urgent to estimate accurately the sustainability of fishing practices and harvesting effort for seaweeds.

Fig. 4
On the left is a map of Chile marking the administrative regions for algae species from 1 to 15. On the right is a horizontal bar graph with the following values. Luga Negra, (5, 11), (160, 10), (10, 14), (40, 8). Luga Roja, (57, 12), (20, 11), (90, 10), (3, 8). Values are estimated.

(Source National Service for Fishery and Acuiculture; in Spanish Servicio Nacional de Pesca y Acuicultura, 2018)

Cumulative landings for each administrative region of Chile of the red alga species G. skottsbergii and S. crispata for the period 2010–2016

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4.4 Threats and Potential Keystone Species for Conservation in the Marine-Terrestrial Interface of Chilean Patagonia

Chilean Patagonia has been subject to rapid socio-environmental changes that bring new threats to biodiversity conservation. These changes could also open up opportunities for increasing the compatibility of local development and conservation.

4.4.1 Recent Threats to Ecosystem Integrity and Biodiversity at the Marine-Terrestrial Interface

The rapid increase in transportation connections and the expansion of tourism to the most remote sectors of the region represent two major threats to biodiversity, as well as opportunities to design sustainable forms of development [33]. The current road system seeks to connect development centers in the Patagonian archipelago region and includes building new roads through the region’s primary forests [77]. New accesses will be opened from the Baker River delta (47° S) to Puerto Natales (52° S) [52], and through Tierra del Fuego Island to the Cabo de Hornos Biosphere Reserve [11]. At the same time, the diminished presence of the Chilean Navy in some marine areas and the opening of Subantarctic channels to commercial shipping and other private development projects imply increasing environmental and social pressures [11]. For example, the exponential growth of the cruise ship tourism industry in areas formerly protected by the Navy involves landings on uninhabited islands and PAs that lack basic information, infrastructure, and park rangers. Unregulated tourism is a threat to the most isolated places in this remote region [43].

Other threats are associated with modes of development that may affect the environmental, economic, and social sustainability of the area. Seven hydroelectric dams have been proposed for construction on the remote Cuervo and Baker rivers [108] the latter being the largest river in the temperate forest biome of South America—with the construction of 5,000 towers for a transmission line over 2,400 km long and 120 m wide, fragmenting and degrading ancient forest ecosystems in one of the largest continuous forest corridors in the world [108].

Forest monocultures and invasive exotic species are another threat to region’s biodiversity [77]. Pinus contorta and Eucalyptus spp. plantations have recently expanded in the Los Lagos and Aysén Regions, replacing the heterogeneity of native ecosystems, and facilitating invasions into degraded native grasslands, steppes, and forests. This expansion produces loss of native species at multiple levels of organization within the ecosystem: soil microorganisms, invertebrates, plants, and vertebrates [29] Invasive plants such as Ulex europaeus, Eucalyptus spp., and Cytisus scoparius continue to expand [7]. The demand for increasing volumes of woodchips from subsidized plantations of eucalyptus (3 million ha in Chile) by the paper industry has encouraged the expansion of monocultures with high water consumption and negative impacts on hydrological cycles [7].

The rapid growth of the salmon farming industry in coastal-marine ecosystems, with an increasing number of net cages anchored directly to the seabed, has disturbed coastal ecosystems and fjord landscapes (40°–54° S). Salmon farming has multiple ecological and social impacts, including marine pollution by antibiotics, eutrophication of marine and lake waters, introduction of a voracious predator, viral infections, and displacement of traditional fishing communities from their ancestral territories [14, 56].

The impact of three exotic mammals has increased in terrestrial, freshwater, and coastal-marine ecosystems of southern South America: beaver (Castor canadensis), North American mink (Neovison vison), and muskrat (Ondatra zibethicus) [21]. In island ecosystems such as the Wollaston Archipelago, invasive carnivores are a major cause of vertebrate extinctions, particularly birds that lack native predators [87]. Since 2000, mink have increased in population numbers and presence in localities in Chilean Patagonia, reaching the southern tip of the region in the Cape Horn Biosphere Reserve in 2001 [19, 80]. Their impact on native fauna has been estimated through diet studies and population censuses of ground-nesting birds. In the Cape Horn Biosphere Reserve, mink diet includes similar proportions (number of food items) of native and exotic mammals, birds, and fish [20, 85,86,89]. Mink represents a critical threat to the biodiversity of terrestrial, freshwater, and coastal-marine ecosystems, including functionally key avifauna at the marine-terrestrial interface [21].

4.4.2 Threatened Species as Biotic Vectors Relevant to Nutrient and Energy Fluxes at the Marine-Terrestrial Interface

The islands of Chilean Patagonia provide habitat for native populations of mustelids (otters), pinniped colonies (e.g. sea lions and elephant seals) and breeding colonies of seabirds (e.g. cormorants, penguins, albatrosses). These vertebrate groups play a key ecological role in the transport of marine nutrients to terrestrial ecosystems [37, 66]. Ten species of birds and mammals that are essential for nutrient flow from sea to land (Table 2) present conservation problems derived from habitat disturbance (e.g. salmon farming), pollution, hunting (otter and pinniped fur trade), and rapid expansion of exotic species such as mink throughout the archipelagic region of Patagonia [38, 88, 89]. Among the species that contribute marine nutrients to terrestrial ecosystems are albatrosses, especially black-browed and gray-headed albatrosses, and four penguin species with abundant breeding colonies in Chilean Patagonia: Humboldt penguin, Magellanic penguin, macaroni penguin, and yellow-plumed penguin. All of these species transport large amounts of nutrients (e.g. N, P, K, Mg) from the sea to the land, modifying the vegetation of the islands [79].

Table 2 Ten species that contribute nutrients at the land-marine interface and that may be emblematic for conservation on the coastline of the Chilean Patagonian archipelago, all of which are currently considered endangered
Full size table

At least 58 bird species affect the marine-terrestrial interface in Chilean Patagonia [66]. On Navarino Island, 65% of these species are resident and only 20% are migratory. The abundance and biomass of birds is especially high at river mouths throughout the region, so this habitat should be considered with special attention in conservation programs.

4.5 Protected Areas with Marine-Terrestrial Interface Relevant to Conservation in Chilean Patagonia

There are currently 40 units of the National System of State Wild Protected Areas (in Spanish Sistema Nacional de Areas Silvestres Protegidas del Estado, SNASPE) located in Chilean Patagonia, representing about 87% of the PA in the country (Table 3). This large concentration of PAs in Patagonia stimulated the creation in 2018 of the “Chilean Patagonia National Parks Network”, in order to plan and manage the parks in the region in an integrated manner, with special emphasis on human communities and the marine-terrestrial interface.

Table 3 Surface area and number of units within the National Protected Areas System according to management category in the three administrative regions within Chilean Patagonia. Areas with coastline are distinguished (*). In the Los Lagos Region, only the areas protected from Reloncaví Sound to the south, including the island of Chiloé. Personal communication (2023) by Mr. Mariano de la Maza, Head State Wild Protected Areas, National Forestry Corporation (in Spanish Corporación Nacional Forestal, CONAF)
Full size table

Twenty of the 39 units include coastline, representing 93% of the total protected area (Table 3). Of the 19 national parks in Chilean Patagonia, 14 (9% of the total area) include coastline. The national parks Cabo de Hornos (58,917 ha), Alberto de Agostini (1,460,000 ha), Bernardo O'Higgins (3,525,901 ha), Kawesqar (2,842,329 ha), Melimoyu (105,500 ha), Corcovado (400,011 ha), Laguna San Rafael (1,742,000 ha), Magdalena Island (249,712 ha) and Guamblin Island (10.625 ha) stand out for their territorial continuity and form a belt of parks with archipelagic zones exposed to the Pacific Ocean that protect habitats for endemic and threatened marine-terrestrial fauna (Tecklin et al., 2021).

Chilean Patagonia includes four biosphere reserves; partially one of them (Bosques Templados Lluviosos de los Andes Australes), and fully the other three: Cabo de Hornos et al. [57]. The Cabo de Hornos Biosphere Reserve (4,884,513 ha) included from its origin the protection of both land (1,917,238 ha) and ocean area (2,967,036 ha), constituting the first demonstrative unit of integrated sea-land management. The lessons learned here could be applied to the other reserves in Patagonia [78, 84]. Together, the core areas of these reserves include national parks and reserves with extensive coastlines, islands, islets, and rocky outcrops. It is important to note that all six nature sanctuaries in Patagonia (315,292 ha) include coastlines. There are also 25 National Protected Assets (272,812 ha), 18 of which have a coastline, and represent 75% of the total area. The RAMSAR site Bahía Lomas, Magallanes Region, is a wetland located on the coastline of Tierra del Fuego Island.

The General Fisheries and Aquaculture Law of 1991 (No. 18,892) created the categories of Marine Park, Marine Reserve, and Benthic Resources Management and Exploitation Areas (AMERBs). Through the AMERBs, fishers’ organizations can establish management areas for a renewable period of two years. The creation of the Ministry of the Environment in 2010 (Law No. 20.417, modification to Law No. 19.300; in Spanish Ministerio del Medio Ambiente, MMA) created and provided administrative authority over the category of Multiple Use Marine and Coastal Protected Area (MU-MCPA). These figures, decreed by the MMA, are under the responsibility of the National Fishing and Aquaculture Service. Eight of the 26 marine protected areas in Chile are in Chilean Patagonia (Tecklin et al., 2021). There are two marine reserves on the island of Chiloé, Pullinque (7.73 km2) and Putemún (7.53 km2), which do not border terrestrial PAs. The two marine parks in the Magallanes Region, Francisco Coloane (15.06 km2) and Islas Diego Ramírez-Paso Drake (140,000 km2), border terrestrial PAs.

The four MU-MCPA are adjacent to PAs: (i) Comau Fjord, Los Lagos Region, adjoins the Private Conservation Initiative (ICP) Huinay Biological Station, managed by the Huinay Foundation; (ii) Pitipalena-Añihue (238.6 km2), Aysén region, adjoins the ICP Reserva Añihue (100 km2); (iii) Francisco Coloane (653.3 km2), Magallenes region, adjacent to Kawesquar National Park; (iv) Seno Almirantazgo (764 km2), Magallenes region, is adjacent to Alberto de Agostini National Park (Tecklin et al., 2021).

The Chiloense and Channels and Fjords ecoregions of southern Chile were prioritized for marine conservation in Latin America in the 1990s [99]. South of the Magellanes Province, the Diego Ramirez Islands-Drake Passage Marine Park was created in 2018, protecting 140,000 km2, most of this area lies within the Channels and Fjords ecoregion of southern Chile, with a section towards the Southern Ocean of the Drake Passage crossed by the Antarctic Circumpolar Current, beyond the southern end of this province [79]. The challenge is to implement and protect this vast marine park, neighboring the Cabo de Hornos Biosphere Reserve.

4.6 Final Reflections

Those ecosystems that integrate coastal-marine environments should have high priority for the conservation of Chilean Patagonian ecosystems. We have documented that in this region, the physical processes include nutrient transport associated with ocean–atmosphere interrelationships, from the ocean to terrestrial ecosystems and vice versa. Freshwater ecosystems, via watercourses, contribute nutrients from terrestrial ecosystems to the oceans. Biotic processes are mediated by large colonies of seabirds and mammal species, such as pinnipeds, which reproduce in island systems and constitute vectors of marine nutrients to terrestrial ecosystems [24].

Environmental institutions must consider the need to conserve the integrity of the coastline and regulate its multiple uses and activities in development plans. Supreme Decree No. 475 was issued in 1994, establishing the National Coastline Uses Policy, which proposes a zoning of the country's coastline in accordance with the realities of each region. Initially, this decree defined that the Undersecretary of the Navy, Chilean Ministry of National Defense, would be responsible to apply this policy to: (a) public beach land located within a strip of eighty meters wide, measured from the line of the highest tide of the coastline; (b) the beach; (c) the bays, gulfs, straits and inland channels; (d) the territorial sea of the Republic of Chile. In 1997, this responsibility was transferred to the Undersecretary of the Armed Forces and Regional Governments of Chile with the task of creating Regional Coastal Border Commissions to develop a cadaster and a zoning proposal [4].

Chilean Patagonia can become a pilot model at the national and international level for this approach to biodiversity conservation, which makes human activities, conservation and development at the land-sea interface compatible.

5 Recommendations

In order to reinforce management and protection measures for the marine-terrestrial interface in Chilean Patagonia, we propose the following recommendations:

  • The SNASPE (administrator until today) and the future Biodiversity and Protected Areas Service of the Ministry of the Environment should be part of the Regional Commission for Uses of the Coastline. Lack of participation in these commissions means that proposals for managing the coastline may be dissociated from the neighboring terrestrial PAs. For example, concessions could be granted in the 80-m strip of fiscal beach for benthic resource extraction activities in areas of great importance for the conservation of threatened bird colonies or marine mammals. It is also recommended that interinstitutional and transdisciplinary collaborations be established and that a landscape-scale approach be used to integrate the conservation of marine and terrestrial ecosystems throughout the archipelagic region of Chilean Patagonia.

  • That D.L. No. 1,939 on Fiscal Assets of the Ministry of National Assets (in Spanish Ministerio de Bienes Nacionales), in its policy of long-term concessions for private projects, regulate the management of the marine-terrestrial interface. Concessions on coastal lands should be in dialogue with local planning of each territory. Finally, the planning and administration of parks and terrestrial reserves, whether public or private, should consider coastal management and be involved in the decision-making of the Regional Commission for Uses of the Coastline.

  • Faced with the antagonism between developmentalist and conservationist positions (see Rozzi and Feinsinger [83]), the United Nations Educational, Scientific and Cultural Organization created the Man and Biosphere Program, MaB), which seeks to integrate human societies and conservation areas to meet social, cultural, recreational and ecological needs [34]. This vision has been implemented through the establishment of an international network of biosphere reserves that today includes a mosaic of unique sites representing the planet's major ecosystems, protected through research, monitoring, education, conservation and sustainable development programs [42, 78]. However, in practice the implementation of biosphere reserves in Chile continues to be a challenge due to the complex management demands, resources, and multiplicity of actors and objectives that must be met [42].

  • A pioneering example of this strategy is the Cabo de Hornos Biosphere Reserve, which may be fundamental for consolidating the Diego Ramirez Islands-Drake Passage Marine Park and could be a demonstration unit for integrating scientific studies, educational programs, special interest tourism, regulated artisanal and industrial fishing, and integrated marine-terrestrial management. Lessons learned in these areas could be implemented in other terrestrial and marine PAs in Chilean Patagonia. On this basis, given the current configuration of large terrestrial and marine parks and reserves in the territory and ocean area of Chilean Patagonia, with a strong presence of the marine-terrestrial interface and a deficiency of regulatory instruments for areas that require integrated management of oceanic and terrestrial ecosystems, we propose the creation of a biosphere reserve that includes all of Chilean Patagonia, from the Chiloé archipelago to the Diego Ramírez archipelago. This large biosphere reserve could establish the compatibility of economic and environmental sustainability and integrate national parks and marine parks as well as terrestrial and marine reserves as core areas, thus making possible territorial planning based on human communities and locally generated traditional and scientific knowledge.