Coastal Belt Linked Classification (CBLC): A System for Characterizing the Interface between Land and Sea Based on Large Marine Ecosystems, Coastal Ecological Sequences, and Terrestrial Ecoregions

Myriad types of coastal classification abound in the literature as there is a long history of attempts to characterize coasts in various ways. All classifications are special purpose in that none provides a universal basis that meets the needs of specializations in different fields of endeavor. This state of affairs is not at all surprising in view of the fact that coasts provide an almost bewildering array of properties or characteristics that are amenable to classification. Special needs have thus fostered the development of special classifications that meet the demands of coastal researchers in fields as diverse as the physical, biological, engineering, social, and managerial sciences. One of the difficulties facing coastal classifiers is that the subject matter is generally rather diverse, depending on the point of view, and that it lacks an obvious degree of discretization. In addition to this classificatory awkwardness there is the problem of defining the geographic span or extent of the attributes that are to be grouped, classed, or ranked. Of the numerous schemes that have been proposed to define the extent of the general concept that has been referred to as the “coastal zone,” perhaps the most prominent are those that delineate the marine environment or maritime zones in terms of units such as coastal waters (3 nautical miles [nm], limit), territorial sea baseline (lowest astronomical tide), territorial sea (12-nm limit), contiguous zone (24-nm limit), exclusive economic zone (200-nm limit), and continental shelf (largely coextensive with the exclusive economic zone) (UNCLOS, 1982). Aside from managerial and sociological approaches to types of coastal classification, prominent endeavors have been featured in the physical and engineering sciences with various classifications geared to geomorphology, geology, tectonics, material composition, and processes (Peters, Husson, and Czaplewski, 2018). Ecological classifications, on the other hand, have been used to classify both marine and coastal environments (e.g., Bailey, 1998; Bartley, Buddemeier, and Bennett, 2001; Burke et al., 2001; Cooper and McLaughlin, 1988; Dinerstein et al., 2017; Finkl and Makowski, 2015; Hayden, Ray, and Dolan, 1984; Makowski, 2014; Makowski, Finkl, and Vollmer, 2015, 2016, 2017; Ramirez-Reyes et al., 2019; Sherman, Aquarone, and Adams, 2009; Short and Woodroffe, 2009). Reviews and summaries of different approaches to coastal classification are provided, for example, by Finkl (2004) and Fairbridge (2004). Most classificatory efforts describe the nature or character of the coast in a shore-parallel manner except in some previous cases where areal approaches were devised for ecological characterizations (e.g., Dolan et al., 1972).

A recent new approach offered in the form of the Biophysical Cross-shore Classification System (BCCS) provided a means for classifying a “coastal belt” in terms of a sea-to-shore-to-inland sequential transect that resulted in the identification of ecological catenary sequences at different levels of investigation. Geomorphological–ecological units were codified using alphanumeric codes that described cross-shore sequences instead of referring to alongshore characterizations. The BCCS was proposed not as an alternative to existing coastal classification schemes but as an additional specialized approach that might be of use to researchers interested in cross-shore geomorphological and ecological succession from the sea to inland uplands. The new system was also proposed as an adjunct to aspects of coastal zonation for those researchers who were not only interested in alongshore variation in environmental parameters but cross-shore sequences as well. To this end, this paper describes how the BCCS can be linked to large-area classifications of marine and terrestrial environments that would show in a concise manner how a range of existing classifications can be combined into a single descriptor of cross-shore catenas. Although it is not a simple matter to make concise large data sets while indicating their spatial interrelationships, it is suggested here that interpretation of coastal satellite imagery combined with collateral interactive data sets provides a key entry to the amalgamation of marine, coastal, and terrestrial environmental units. The means of achieving such linkages is described in the following section.

The BCCS investigation of coastal biophysical features and environments (e.g., habitats, landforms, geoforms, ecosystems; Bailey, 1998; Burke et al., 2001; Dolan et al., 1972; Hayden, Ray, and Dolan, 1984; Fairbridge, 2004; Finkl, 2004; Finkl, Makowski, Vollmer, 2014; Isla, 2009; Kelletat, 1989, 1995; Kelletat, Scheffers, and May, 2013; Klemas et al., 1993; Makowski, Finkl, Vollmer, 2015, 2016, 2017; McGill, 1958; Wang et al., 2015; Zhang et al., 2011) requires the inclusion offshore, inshore, and onshore data that comprise a coastal belt (see definition in Finkl and Makowski, 2020c). This kind of coastal information may be acquired from original research surveys or assimilated from existing sources. Aerial photographs are good for very detailed work, but satellite imagery as provided by Google Earth Pro is available in myriametric scales by zooming in or out of a selected scene. Use of Google Earth Pro satellite imagery is advantageous because of its global coverage of the world's coasts (see the example of Scheffers, Scheffers, and Kelletat, 2012), which provides a valuable data source that can be interpreted at desired scales (depending on the resolution of the imagery).

The advantage of referencing an extant environmental classification system (e.g., Bailey, 1998; Burke et al., 2001; Dolan et al., 1972; Hayden, Ray, and Dolan, 1984; Klemas et al., 1993; Sherman, Aquarone, and Adams, 2009; Zhang et al., 2011) is that it can be applied to terrestrial and marine portions of a satellite image comprising part of a coastal belt. Because of the multifaceted nature of the coast, land- and marine-based systems must be merged to provide coherent and complete descriptions of coastal belts. The basic procedure or method for compiling Coastal Belt Linked Classification (CBLC) codifications is to peruse interactive online platforms to access the appropriate numeric codes for marine ecosystems (i.e., Large Marine Ecosystems, LME) (e.g., Sherman, Aquarone, and Adams, 2009) and terrestrial Ecoregions (ER) (e.g., Ecoregions 2017 - Resolve) (Dinerstein et al., 2017). That information can then be added as prefixes and suffixes to the Coastal Ecological Sequence (CES; Finkl and Makowski, 2020a,b,c). Assembly of this information, as described by Finkl and Makowski (2020c), provides enough essential data to characterize a coastal belt in terms of linked cross-shore classification that takes the codified form of LME+CES+ER (i.e. Large Marine Ecosystem prefix code number plus the Coastal Ecological Sequence plus the Ecoregion suffix).

Implementation of the codification procedure involves the preparation of a standardized header that precedes satellite images for portions of coastal belts. Headers contain the following information in this order: Coastal Belt Location (Latitudinal Range); Large Marine Ecosystem (LME); Planview or Oblique View; Shoreline; Environments and Habitats; Dominant Catenary Sequence (DCS); Coastal Ecological Sequence (CES); Terrestrial Biogeographic Realm and Biome; Ecoregion (ER); Coastal Belt Linked Classification (CBLC); and lastly, a translation of the code sequence in the CBLC. Names of Large Marine Ecosystems and Ecoregions are written out in full and accompanied in parentheses by their respective numbered codes. For example in Figure 1, the LME is the Indonesian Sea with a number code of (38) and the ER is the Sulawesi Lowland Rainforests with a number code of (156).

The Coastal Belt Linked Classification (CBLC) essentially amalgamates the LME, CES, and ER into a single coherent codification sequence that characterizes the marine ecosystem, coastal interface, and terrestrial ecoregion. This alphanumeric code is subsequently followed by a plain English translation that expands the codified concision. The translation thus identifies archetypes and sub archetypes that make up the coastal belt, as shown in the CES. Following the header is the actual satellite image. The image should be annotated with a cross-shore transect that clearly shows the location and direction of classification, usually in the form of a directional arrow. The LME and ER are normally shown outside of the arrow‘s graphically included codifications in their respective environments (cf. Figure 1). Lastly, the annotated satellite image should be followed by an expanded caption that identifies the location of the satellite image with latitude and longitude, includes any geomorphological features, lists the particular climate, and describes the flora and fauna. Also included are some additional geographical landmark locators to place the image in a regional context and inform the reader of dominant spatial relationships.

Execution of these simple procedures provides an orderly presentation of data in a consistent format that facilitates perusal of multiple images of coastal belts. Procedural adaptation of data presentation, graphic displays, and succinct verbal and numerical summaries organizes much information in an easy-to-use format that should be regarded as a methodological template. The results of these procedures are illustrated and elucidated in the next section of the paper.

Results of the CBLC procedure are summarized here in six examples with one each from equatorial, tropical, subtropical, middle-latitude, subpolar, and polar latitudinal zonations as respectively represented by these general locations: South East Sulawesi, Indonesia; island of Socortra, Yemen, Gulf of Aden; Shark Bay, Western Australia, Australia; Graham Island, British Columbia, Canada; Lituya Bay, Alaska, U.S.A.; and Chaunskaya Guba, Chukotka Autonomous Okrug, Siberia, Russian Federation. Different types of information are provided for the LME and ER units in an effort to show the kind and range of data that are available for these marine and terrestrial ecosystems, and to emphasize the large amount of collateral data that is added to the Coastal Ecological Sequence (CES).

This example CBLC classification of an equatorial atoll (3°30′11″S by 123°04′50″E) occurs about 72 km off the southeast coast of South East Sulawesi, Indonesia (Figure 1). Pulau Padea-besar (also known as Pulau Padei Darat or Padei Darat Island) is located in the province of Sulawesi Tenggara, in the central part of the country about 1800 km east of the capital Jakarta. The area of this atoll is about 4.8 km², stretching 2.8 km in a north-south direction and 4.9 km in an east-west direction. These types of orbicular coral islands are sometimes referred to as circular groups of coral islets or lagoon-island (e.g., Woodroffe and Biribo, 2011). Other definitions describe atolls as “annular reefs enclosing a lagoon in which there are no promontories other than reefs and islets composed of reef detritus” or in a morphological sense a ring-shaped ribbon reef enclosing a lagoon. The term faro is used in reference to smaller annular reefs within a central enclosed lagoon or depression (e.g., McClanahan, Shepard, and Obure, 2000; McLean, 2011). Shown in this image are most of the common morphological parts that are associated with these distinctive biogenic buildups in tropical and subtropical seas (e.g., rim reefs that drop off to deep water, reef flats, backreef areas with patch reef corals, central lagoon, inlet or deepwater channel connecting to the open sea, and in this case a surmounted sand cay that is vegetated with mangrove forests). The equatorial climate of this coastal marine area is referred to in the modified Köppen climate classification system as Am (Tropical Monsoon Climate) (cf. Kottek et al., 2006; Peel, Finlayson, and McMahon, 2007).

The BCCS cross-shore transect (large translucent red-colored arrow) could be drawn in different directions across the atoll, but the present position was selected to best describe the nature of the environment where there is an orbicular-shaped coral reef surrounding a central lagoon that is connected to the ocean via a small inlet. A sand cay has accumulated on the southwestern margin of the atoll where vegetation has taken hold. The curved coral reef is identified by the BCCS alphanumeric code 1Cr_at, which is followed by the code for the open central lagoon (L_op) that merges into the calcareous beach (Be_ca) on the western flanks of the cay that carries coastal mangroves (W_ma) and interior rain-forest (mangrove) vegetation (W_ma) (cf. Table 1). If the transect was continued in a southeastward direction the codification for beach and wetland archetypes would repeat.

The Indonesian Sea (LME38) is situated at the confluence of the Pacific and Indian Oceans, and is bordered by Indonesia and East Timor. It covers an area of about 2.3 × 10⁶ km² and contains about 10% of the world's coral reefs (Sea Around Us, 2007). About 0.5% of this LME is covered by mangroves and 1% by coral reefs (Giri et al., 2011). Palau is separated from the Coral Triangle (a roughly triangular area of tropical marine waters of Indonesia, Malaysia, Papua New Guinea, Philippines, Solomon Islands, and Timor-Leste) by several hundred kilometers of open water that limit the exchange of marine species between these areas. Although Palau's roster of species is a subset of species found inside the Coral Triangle (i.e. less species richness), there are over 1400 species of fish, about 300 species of marine sponges, and at least 500 diverse coral species. There are only nine known species of giant clams in the world, for example, and Palau has seven.

Sulawesi Lowland Rainforests (ER156) are commonly found toward the interior of the larger, wetter uninhabited atolls (as shown in the image). Located behind the strand zone but often mixed with strand vegetation, they usually have an outer shrubby fringe of Scaevola taccada. Small, well-formed Pemphis acidula are common on rocky coasts, whereas tall Casuarina litorea trees are often found on leeward coasts. Humus from decaying vegetation provides a sustaining recycling of nutrients. Common species include Intsia bijuga, Psychotria spp., and Clerodendrum inerme, as well as endemic palms (e.g., Gulubia palauensis and Ptychosperma palauensis), forest trees (e.g., Semecarpus venenosus, Premna obtusifolia, Cordia spp., Bikkia palauensis), and understory plants (e.g., Pandanus spp., Dracaena multiflora).

There are over 1,400 species of fish, about 300 species of marine sponges, and at least 500 diverse coral species in Palau. There are only nine known species of giant clams in the world and Palau has seven. Bird species restricted to Palau include doves, owls, swiftlets, and passerines. Terrestrial mammals include the Palau flying-fox (Pteropus pelewensis) and the rare insectivorous sheath-tailed bat (Emballonura semicaudata palauensis). The saltwater crocodile (Crocodylus porosus) is at the edge of its range in Palau.

This CBLC example of a tropical carbonate beach (12°20′27″N by 53°34′23″E) occurs on the central southern shore of the island of Socotra, Yemen, in the Gulf of Aden (Figure 2). Lying 240 km east of the Horn of Africa and 380 km south of the Arabian Peninsula, Socotra Island is located between the Guardafui Channel and the Arabian Sea, and is the largest of four islands of the Socotra Archipelago making up 95% of the landmass of the Socotra Archipelago. Due to its remoteness, isolation, and endemic biomes, Socotra has been described as “the most alien-looking place on Earth.” This coastal scene is remarkable for the wide pure white carbonate beach and dune sands that stand in contrast to the turquoise waters of the sea and the grayish brown arid hinterland. Some of the dune sands are climbing the cliff face as seen, for example, under the cross-shore transect (translucent red-colored arrow). Sub archetypes making up the CES tetrasequent catena are marked in the transect arrow by the BCCS notation as 7Be_caDu_dsCl_se,vc10%U_de, which translates to straight tropical carbonate beaches and extensive dune sheets at the foot of mostly unvegetated (∼10% cover) limestone cliffs that are surmounted by desert uplands. The Arabian Sea is denoted by the LME32 and the terrestrial ecoregion ER105 and when combined respectively as a prefix and suffix to the BCCS code they are morphosed into the CBLC code as (LME32)7Be_caDu_dsCl_se,vc10%U_de(ER105), which elucidates marine and terrestrial ecosystems with the sub archetypes in the DCS forming a Beach-Dune-Cliff-Upland (Be-Du-Cl-U) cross-shore tetra-sequent catena. The climate here is classified as BWh, Hot Tropical Desert.

The Arabian Sea (LME32), which lies in the northwestern Indian Ocean between the Arabian Peninsula and India, is bordered by Bahrain, India, Iran, Iraq, Kuwait, Oman, Pakistan, Qatar, Saudia Arabia, Somalia, United Arab Emirates, and Yemen. It covers an area of about 4 × 10⁶ km² and contains about 2% of the world's coral reefs.

Botanically, the Socotran Archipelago in ER106 is known for its assemblage of endemic and unusual species. Of the 850 recorded plant species, approximately 230 to 260 (about 30 percent) are endemic. There are also ten endemic genera: Ankalanthus, Ballochia, Trichocalyx, Duvaliandra, Socotran-thus, Haya, Lachnocapsa, Dendrosicyos, Placoda, and Nirarathamnos; and one near-endemic family (Dirachmaceae). Some of the plants on Socotra represent the last surviving members of their genus. The limestone plateau and the Hagghier Mountains are the richest areas for endemic plant species, but endemics are found throughout the island in every type of vegetation.

This example of a subtropical tidal sand flat (25°55′12″S by 113°56′59″E) separates Shark Bay from Hamlin Pool on the central west coast of Western Australia (Figure 3). The Shark Bay area in the Gascoyne Region is the most westerly point in Australia and a UNESCO World Heritage Site. The land area in the upper left-hand corner of the image is Faure Island (a pastoral lease and nature reserve) and the sandy area barely above the water directly east is Pelican Island. These tidal flats separate the hypersaline Hamlin Pool to the south from Shark Bay to the north, which connects with the eastern Indian Ocean. The sand flats, which range from about 2 to 4 m below the surface of these exceptionally clear waters, occur between deeper-water channels that range from 2 or 3 m deep up to about 10 m depth as in the upper right-hand corner of the image.

The cross-shore transect extends from mid bay in LME44 (West-Central Australian Shelf) in a general northwesterly direction to the terrestrial upland that is part of ER207 (Carnarvon Xeric Shrublands). The tri-sequent catena making up the DCS as Flat-Beach-Upland (F-Be-U) is refined in the CES to 7F_sa,sv,tcBe_ca,siU_sr. When the CES is amalgamated with the LME prefix and ER suffix this CBLC results: (LME44)7F_sa,sv,tcBe_ca,siU_sr(ER207). Translation of the codification is verbalized as ‘West-Central Australian Shelf Large Marine Ecosystem linked to a straight subtropical coastal belt with calcareous sandbanks, submerged vegetation, and tidal channels backed by a mixed carbonate-silicate beach grading to upland scrub vegetation connected to a Carnarvon Xeric Shrublands Ecoregion.'

The West-Central Australian Shelf (LME44) extends off Western Australia from Cape Leeuwin (∼34.5°S) to Northwest Cape (∼22°S). This LME owes much of its biogeographic unity to the respective connecting influences of the West Australian Current, a northward flow coming from the circulation pattern of the counterclockwise Indian Ocean gyre, and the Leeuwin Current (LC), the only west-coast poleward-flowing eastern boundary current in the Southern Hemisphere. The LC is a major southward flow of warm, low-nutrient, buoyant tropical water along this LME's relatively narrow continental shelf and is responsible for tropical reefs and associated marine flora and fauna flourishing farther south than anywhere else in the world. In addition to these regional-scale ocean currents, wind-driven coastal countercurrents dominate the circulation close to shore during the austral spring/summer period. Although high energy from swell is a major feature of LME44, waves are restricted or blocked in embayments and lagoons, with sheltered highly biodiverse protected habitats occurring behind offshore limestone reefs in many localities. The extremely narrow shelf, in some areas only 40 km wide, covers an area of nearly 550,000 km², about 2% of which is gazetted as a marine protected area(MPA) that contains 0.37% of the world's coral reefs (Sea Around Us, 2007; www.dec.wa.gov.au).

Carnarvon Xeric Shrublands (ER207) cover an area of 90,500 km² bounded by the Indian Ocean in the west from the Peron Peninsula in Shark Bay up to the North West Cape. The associated ecoregions include the Pilbara shrublands to the northeast, the Western Australian Mulga shrublands to the east, and the Southwest Australia savanna to the south. The terrain is generally low, and the vegetation varies with the underlying geology, which consists mostly of recent alluvial, aeolian, and marine sediments over cretaceous strata. This dry region receives less than 250 mm of rainfall per year. The climate of this region is on the border of BSh (Hot Steppe Climate) seaward and BWh (Hot Desert Climate) landward.

This example of a middle-latitude beach ridge plain (54°5′9″N by 131°43′24″W) occurs on the northeasternmost point of Graham Island, British Columbia, Canada (Figure 4). Graham Island is the largest island in the Haida Gwaii Archipelago (formerly the Queen Charlotte Islands), lying off the coast of British Columbia. About 2 km wide by 13 km long, this series of ridges contains numerous interridge lakes and wetlands. The net littoral drift in this scene, which is from left to right, built this example of a high middle-latitude beach ridge plain. The stranded beach ridges are vegetated with trees and shrubs, with the intervening low-lying swales containing marsh vegetation associations. The warm temperate climate here is classified as Csb, Marine or Maritime Climate and sometimes also referred to as a Marine West Coast Climate.

The annotated cross-shore transect (large translucent red-colored arrow) trending NW to SE defines the tri-sequent archetype catena in terms of a DCS as Beach-Beach Ridge-Wetland (Be-Br-W) that in turn is expanded into a CES as 2Be_siBr_spW_mr (curved silicate beach - strandplain – marsh wetland). By prefixing the large marine ecosystem (LME) and suffixing the ecoregion (ER) to the CES, the BCLC concatenation becomes (LME2)2Be_siBr_spW_mr(ER365) where the attributes of the Gulf of Alaska Large Marine Ecosystem (LME2) and the Queen Charlotte Islands Conifer Forests (ER365) inform a complete picture of cross-shore environmental sequencing.

The Gulf of Alaska Large Marine Ecosystem (LME2) lies off the southern coast of Alaska and the western coast of Canada. Separated from the East Bering Sea LME by the Alaska Peninsula, its climate is subarctic. The cold Subarctic Current, which flows from the east, divides in two parts at about 53°N where Queen Charlotte Sound, Canada, forms a boundary between the Gulf of Alaska and the California Current LME. The Gulf of Alaska Large Marine Ecosystem is sensitive to climate variations on time scales ranging from the interannual to the interdecadal.

This connected ecoregion (ER365) comprises the Queen Charlotte Islands Conifer Forests. Plant species in low sandy areas include pickleweed, saltgrass, seaside plantain, sandspurry, and milkwort, whereas low silty areas have arrow grass and spikerush. Conversely, those areas less inclined to be inundated by saltwater have such species as Lyngbye's sedge, common three-square, narrowleaf bur-reed, and water horsetail. The low-elevation coastal forest shown in the image's dryer sections includes productive stands of western hemlock (Tsuga heterophylla), western red cedar (Thuja plicata), and amabilis fir (Abies amabilis).

Characteristic wildlife in ER365 includes black-tailed deer (Odocoileus hemionus), black and grizzly bears (Ursus americanus and U. arctos), mountain goat (Oreamnos americanus), wolf (Canis lupus), mink (Mustela vision), Northern river otter (Lontra canadensis), blue grouse (Dendragapus obscurus) and other waterfowl, moose (Alces alces), woodland caribou (Rangifer tarandus spp.), beaver (Castor canadensis), red fox (Vulpes vulpes), and marten (Martes americana).

This Subpolar coastal glacier (58°28′03″N by 137°15′48″W) lies on the Gulf of Alaska about 60 km northwest of Lemesurier Island, the second-largest island in the Icy Strait between Chichagof Island and the mainland of the Alaska Panhandle in the U.S. State of Alaska, and about 22 km southeast of Lituya Bay (Figure 5). This satellite scene occurs on the seaward margin of Glacier Bay National Park and Preserve. This lobe is one of the several coastal termini of the glacial ice field flowing seaward from Mount La Perouse, about 13 km inland. The interesting patterns shown in this image reflect distinct coastal environments that range from a morainic shoreline to forested ground moraine (lower right-hand corner of image) to unvegetated ground and recessional moraine fields surrounding the glacial snout to snow and ice surfaces of the retreating glacier itself. Marginal (lateral) moraines occur on the eastern and western flanks of the glacier. The upper center of the image shows a heavily crevassed area where the glacier is breaking up and retreating. Outflowing glacial meltwaters are bringing fine-grained suspended sediment in the form of glacial flour to the shore, causing the highly turbid coastal water. Holocene till deposits mostly characterize the coastal region here. The coastal boreal climate is classified as Dfc, Subarctic or Subpolar Climate. The high elevations just inland from the coast are classified as ET, Tundra Climate and EF, Ice Cap Climate.

The BCCS cross-shore transect is a simple moiety or di-sequent catena as shown in the annotated red-colored arrow that transits shore to glacier. This elementary cross-shore ecological sequence is characterized by morainic materials (e.g., till) along the shore that grade into recessional moraines in front of the snout of the mountain glacier. The large translucent red-colored arrow that is annotated to show a curved coastal belt composed of till and ice is concatenated in the BCCS di-sequent DCS archetypes as Till-Ice (T-I) and refined in the CES as 2TI_gl where the distinction is the identification of the glacial ice sub archetype. The appendage of LME2 as a prefix and ER360,420 as a suffix to the CES concatenation produces the BCLC notation (LME2)2TI_gl(ER360,420) that translates in plain English to: Gulf of Alaska Large Marine Ecosystem linked to a curved subpolar coastal belt with glacial till forming a ground moraine that is unvegetated and surmounted by ice at the terminus of a glacier connected to a Northern Pacific Alaskan Coastal Ecoregion (ER360) grading inland to Pacific Coastal Mountain Icefields and Tundra Ecoregion (ER420). Although the BCLC notation is simple, the description of cross-shore ecosystem succession is complicated by the mountainous terrain along the coastal belt. The steep mountains so close to the shore bring icefields and tundra into considerations of coastal belt environments. Steep, rugged mountains covered by many active glaciers are typical of this ecoregion where elevations range from sea level to more than 4,500 m. Higher parts of the ecoregion are buried in ice fields from which valley and piedmont glaciers radiate, often reaching the coast. Slope gradients for most of the region are greater than 7°; slope gradients for 5% of the region exceed 20°.

The principal nature of ER360 is alpine slopes barren of vegetation or dwarf and low scrub communities in areas where vegetation does occur. There are many areas where needleleaf forests, originating in adjacent, lower-elevation ecoregions, colonize mesic sites along drainageways. Dwarf scrub communities are typically dominated by mountain heath (Phyllodoce aleutica). Associated shrubs include cassiope (Cassiope mertensiana and C. stelleriand), meadow-spirea (Luetkea pectinata), bog blueberry (Vaccinium uliginosum), and dwarf blueberry (V. caespitosum). Low scrub communities dominated by ericaceous shrubs (for example, Cladothamnus pyrolaeflorus) form dense thickets at lower elevations in the ecoregion where snow cover persists until late spring.

The Pacific Coastal Mountain Icefields and Tundra ecoregion (ER420) consists of steep, rugged mountains that stretch from the Kenai Peninsula along the Gulf of Alaska Coast and the Canadian/Alaskan border to the southern end of the Alaska panhandle. In Canada, this ecoregion encompasses the extreme southwestern corner of the Yukon Territory and parts of the coastal mountains in British Columbia south to Portland Inlet. Similarly to ER360, elevations in this ecoregion range from sea level to over 4500 m, and slopes generally are steeper than 7°, ranging to over 20°. In this extreme northern part of the ER420, the Seward, Hubbard, and Malaspina glaciers are the dominant physiographic features and the area is part of the largest nonpolar icefield in the world. The mountains are composed of gneissic and granitic rocks, and are cut into several segments by large, steep-sided transverse valleys. Isolated patches of permafrost occur at elevations above 2500 m.

This polar deltaic region (68°50′24″N by 170°36′02″E) of the Chauan and Palyavaam rivers empties into an Arctic bay, Chaunskaya Guba, in Chukotka Autonomous Okrug of eastern Siberia, Russian Federation (Figure 6). Chaunskaya Guba opens to the East Siberian Sea 260 km east of Kolyma Gulf and 150 km west of De Long Straight. The delta in the vicinity of Rytkuchi is characterized by meandering distributaries of these two main river systems, point bars, cutoff meanders, permafrost terrain with meltwater lakes, and marshes, whereas on the bayside there are mudflats up to one kilometer in width. About 34% of the world's coastlines are covered in permafrost, which absorbs the impact of ocean waves and protects against coastal erosion as seen here in this image. Sea ice, as shown here in the light-colored area on the far left-hand side of the image, helps block waves from reaching the shore.

The BCCS cross-shore transect is a simple penta-sequent catena as shown in the annotated red-colored arrow (Figure 6) that transits the shore to a periglacial and permafrost coastal alluvial plain, as shown in the translucent red-colored arrow. The Dominant Catenary Sequence (DCS) shown in the satellite image works out to the cross-shore sequence of archetypes as follows: Ice-Flat-Barrier-Beach-Wetland (I-F-Ba-Be-W). The more detailed Coastal Ecological Sequence (CES) shown in the cross-shore transect expands the archetypes in sequential sub archetypes as follows: 2I_stF_sa,muBa_mbBe_siW_mr. The curved coast (cf. Table 1) is marked by a shore-fast ice accumulation that is denoted by the sub archetype code 2I_st that fronts a sandy and muddy tidal flat (F_sa,mu) forming a muddy barrier sub archetype (Ba_mb). The narrow silica beach sub archetype (Be_si) marks the boundary between the coastal belt barrier and landward wetlands composed of marsh (W_mr). Because of the scale of presentation and complexity of the shore sub archetypes making up the seaward part of the coastal belt, the codifications are assembled alongshore within the cross-shore transect for clarity. The alongshore extent of the tidal flat sub archetype is indicated by lettering outside of the cross-shore transect, as is the notation in the location of the open lagoon sub archetype (L_op). Completion of the CES catena is achieved by adding the Large Marine Ecosystem prefix and Ecoregion suffix to form the CBLC (LME54)2I_stF_sa,muBa_mb Be_siW_mr(ER772) that recognizes the Chukchi Sea marine ecosystem (LME54) and the Chukchi Peninsula Tundra (ER772). The CBLC codification translates to ‘Chukchi Sea Large Marine Ecosystem linked to shore ice fronting a curved polar flat backed by a mainland barrier (silica) beach that grades into wetland marshes connected to the Chukchi Peninsula Tundra Ecoregion’ (cf. Figure 6). The boreal climate around Chaunskaya Guba is classified as Dfc, Subpolar or Subalpine Climate.

The Chukchi Sea, sometimes also referred to as the Chukotsk Sea or the Sea of Chukotsk, is a marginal sea of the Arctic Ocean. Its western boundary is marked by Long Strait, off Wrangel Island, and by Point Barrow, Alaska, in the east beyond which lies the Beaufort Sea. The southernmost limit is the Bering Strait, which connects it to the Bering Sea and the Pacific Ocean. The Chukchi Sea Large Marine Ecosystem (LME54) is a shallow Arctic shelf sea located north of the Bering Strait. The Chukchi Sea LME54 has a surface area of about 1.4 × 10⁶ km², and about 50% of the shallow planar seabed lies less than 50 m deep; the central part of the Chukchi Sea is approximately 500 km wide and about 800 km wide on the northern shelf edge.

The Chukchi Peninsula tundra ecoregion (ER772) covers the northeastern coast of Russia, stretching eastward about 700 km from the mouth of the Lena River in the northwest to the eastern tip of the Chukchi Peninsula. The mostly treeless Arctic alluvial plains, which are saturated by surficial groundwater lenses and permafrost at depth, are occasionally surmounted by small mountains up to 1,000 m in elevation. Lying north of the treeline, Ecoregion 772 contains only scattered communities of brush among the widespread tundra floral cover that includes hundreds of species of lichen and moss. Because of moderating effects of marginal seas that enhance summer daytime temperatures above 10°C, the climate is rather milder for this latitude than what might otherwise be anticipated. The chilly waters along the coast provide important habitat for numerous marine mammals, whereas brown bear, sable, lynx, ermine, mountain hare, and mink can be found in the adjacent terrestrial lands. Numerous rare and endangered species inhabit ER772 and among those listed in the Red Data Book of the Russian Federation are the polar bear, bighorn sheep, narwhal, humpback whale, finback whale, grey whale, blue whale, razor back, and 24 specific bird species. Many colonies of migrating birds visit Ecoregion 772, which lies in the Palearctic Biogeographical Realm and Tundra Biome.

The Coastal Belt Linked Classification (CBLC) builds upon the principles of the BCCS [Biophysical Cross-shore Classification System; as described by Finkl and Makowski (2020a,b,c)] to provide a universal means of classifying coastal belts worldwide. Both the CBLC and BCCS simplify the complexity of tripartite environmental systems (marine, coastal, terrestrial) that are interlinked along- and cross-shore via marine environments and terrestrial habitats that are separated by interfacial coastal transition zones (i.e. coastal belts).

The BCCS is constructed on different levels of specificity: a Level I investigation results in the formulation of a cross-shore archetypical DCS (Dominant Catenary Sequence: dominant catena composed of archetypes); a Level II investigation produces a coded sequence of cross-shore archetypes and sub archetypes in the form of the CES (Coastal Ecological Sequence: dominant catena composed of archetypes, sub archetypes, and shore-parallel configuration shapes); and a Level III investigation uses verbal descriptions and ancillary information to build a précis or synopsis that includes Level I and Level II data (Finkl and Makowski, 2020a,b,c).

The CBLC, however, proposes a new Level IV investigation, which now expands upon the previous BCCS procedures to incorporate information related to Large Marine Ecosystems (LME) and terrestrial Ecoregions (ER). Coastal belts can now be characterized as a Level IV investigation by linking Large Marine Environments (LME) and terrestrial Ecoregions (ER) as part of the coded sequence (catena). In doing so, a more complete classification of the coastal belt is achieved by integrating offshore marine environments and interior regions with the transitional coast.

It should be emphasized that the CBLC is an alternative, or supplemental, method to traditional classification systems. The method is based on interpretation of coastal belt satellite imagery that can be acquired from any appropriate sources, such as Google Earth Pro. Coastal belts are flexible environments that have variable alongshore and cross-shore dimensions depending on the scale of the imagery and spatial extent of the features being characterized. As shown in this paper, one satellite image scene can be used to illustrate the CBLC procedure, but it should also be noted that separate image scenes can be stitched (i.e. mosaicked) together to cover larger swaths of coastal belts as required by research needs.

The omphalos of the CBLC is the interposition of the LME (Large Marine Ecosystem) and ER (Ecoregion) units with a CES (Coastal Ecological Sequence), using the LME as a prefix and ER as a suffix to the archetypes and sub archetypes used in the CES. In this way, a Level IV concatenation is achieved: LME+CES+ER. This codification provides a clear and concise characterization of a coastal belt by including marine, coastal, and terrestrial units into one formulation. One advantage of this method is that LME and ER units have already been established and can be accessed via interactive Internet sites, making acquisition of relevant environmental data relatively simple. Even though the LME and ER units were recommended because of their accessibility in electronic format, it should also be noted that other environmental descriptions are available and can be used instead of the ones suggested here. Moreover, the CBLC is completely flexible and not tied to one particular environmental unit or system of classification. The concept presented here is a procedure for organizing the description and classification of coastal belts and as such it is not restricted to the same LME or ER units applied in this study. Another caveat is that LME and ER units can be somewhat difficult for identifying precise definitions of boundaries. The procedures used to define the LME and ER units are no doubt available from public and private research agencies and academic divisions that prepared the electronic maps and data sets, but this information is not readily available on respective home pages. Nevertheless, the units provided are useful and have been described to various degrees of specificity where the more accessible and economically important regions have been more intensively described than extremely remote zones.

An advantage the CBLC has over shore-parallel classification schemes in that it provides a rational basis for describing or characterizing large swaths of coastal belts in an orderly manner by linking marine, coastal, and terrestrial units in the natural order by which they occur. The resulting catenas (cross-shore sequences) thus provide a more comprehensive appreciation of interlinked facets that make up a coastal belt. Therefore, a CBLC Level IV investigation informs the investigator of the true nature of a coastal belt by showing how marine, coastal, and terrestrial environments are linked in reality to form the complex environmental setups seen across the coast.

The method discussed here brings order to the complicated biophysical environments that make up the coast. Because coasts per se are not independent of adjacent marine environments or terrestrial hinterlands, interpretation of satellite imagery with the CBLC becomes an ideal way to readily describe any particular coastal belt at any latitude. One advantage of Google Earth satellite imagery is that it provides free worldwide coverage in an easy-to-use format via Google Earth Pro. Although there are many other sources of commercial and government satellite imagery, one would be hard pressed to find easy accessibility to the world's coastal belts at a one-stop shop. That is why the CBLC was developed around such an accessible global platform.

The CBLC (Coastal Belt Linked Classification) was proposed as a methodology for characterizing and classifying coastal belts, as interpreted from satellite imagery, using a cross-shore transect to identify sequential marine to terrestrial geomorphological-ecological sequences. The basic BCCS (Biophysical Cross-shore Classification System) coastal classification is a concatenation of archetypes and sub archetypes that are encountered in a landward direction from the sea to interior terrestrial upland environments and recognized as a Coastal Ecological Sequence (CES). Cognizing the coast as an interfacial or transitional zone between land and sea, the core CES codification was preceded by adding Large Marine Ecosystem (LME) numerical codes and followed by terrestrial Ecoregion (ER) numbers to produce the CBLC Level IV concatenation: (LME) CES (ER). This cross-shore formulation recognizes the spatial associations of biophysical environmental units that make up coastal belts and uses a shorthand notation to succinctly identify the essential or primary characteristics of the world's coastal systems. The classificatory scheme described here is open ended and thus flexible enough to incorporate more detail or new units as required for specialized coastal research efforts.