sandy coastal vegetation chapters/c20/e6-142-tb-08.pdf · of the vegetation of these sandy coastal...

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INTERNATIONAL COMMISSION ON TROPICAL BIOLOGY AND NATURAL RESORCES - Sandy Coastal Vegetation - D.S.D. Araujo, M.C.A. Pereira

SANDY COASTAL VEGETATION D.S.D. Araujo Department of Ecology, Rio de Janeiro Federal University, Brazil M.C.A. Pereira Herbarium, Rio de Janeiro Botanical Garden, Brazil Keywords: Vegetation types, flora, community structure, diversity, distribution, conservation Contents 1. Introduction 2. Landforms and climate in coastal areas 3. Vegetation types and community structure 4. Life forms 5. Species diversity and geography 6. Conservation Glossary Bibliography Biographical Sketches Summary Sandy coastal ecosystems are severely threatened all over the Tropics due to their location near the ocean, ideal spots for tourism, recreation and summer homes. They also provide environmental services to man in the form of buffer zones against storm surges, reduced beach erosion, and recreation areas, among others. Therefore understanding the ecology of the organisms that inhabit these regions is extremely important if humankind is to conciliate the use of the environment with preservation of ecological processes so as to take advantage of the services provided by these ecosystems.. Our aim in this chapter is to describe what we know about various aspects of the vegetation of these sandy coastal plains. To form a backdrop for this scenario, we first define the landforms that underlie this coastal vegetation and the environmental factors that have the greatest influence on the plants. Then we stress the extremely heterogeneous nature of the underlying substrate and how this is reflected in vegetation physiognomy and structure. We also discuss variations in species diversity at various scales and how these plants are distributed geographically. Finally, we consider various conservation aspects of these ecosystems. 1. Introduction Sandy coastal deposits are found on shores all over the world, from polar latitudes to the tropics. The forces that create, mold and destroy these deposits are basically wind, sea level oscillations and the presence or absence of vegetation. Time is also an important factor in this process, especially on prograding shorelines. A profile of these sandy deposits represents a time series, from young beach sands to older, often stabilized,

©Encyclopedia of Life Support Systems (EOLSS)

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inland deposits. Ecological zonation is clearly demonstrated on sandy coasts especially as one walks from the beach inland. The forces mentioned above create an extremely varied landscape, from tall dunes and beach ridges where the water table lies deep below the soil surface to wet slacks that lie between these dunes and beach ridges, some of which are permanently flooded. This variety is reflected in the diversity of vegetation types and relatively large numbers of plant and animal species that are generally found along the coast. The plants of these sandy plains are grouped together in communities, or plant formations, that owe their special physiognomy to habitat conditions found at the site, to the kinds of species that have managed to arrive and become established locally, and to the length of time these species have been growing together, free from major disturbance. The long-term evolutionary history of the coastal plain during the Quaternary period and the kinds of ecosystems that occupy the surrounding landforms are two other factors that exert a strong influence on the vegetation physiognomy and floristic composition of each area of coastal plain. Coastal plains can be regarded as islands scattered along the coastline because they are often isolated within amphitheaters formed by coastal mountain ranges or rocky headlands, bordering on bays or coves. Or they may be isolated from other areas of sandy coastal plains by the estuaries of large rivers. Extensive dune fields often develop on low-rainfall coasts in the Tropics (e.g., Lençois Maranhenses, Brazil; Skeleton Coast of Namibia, Africa) and may extend for many kilometers inland. These often lie near a cold water upwelling that brings nutrients to the surface from the depths of the ocean, thus providing rich fishing grounds (e.g., coastal Peru; Cabo Frio region, Brazil). Coastal plain ecosystems are seriously threatened because of their location beside the sea. Summer houses and seaside resorts spring up overnight in many parts of the Tropics, resulting in biodiversity loss, environmental disturbance and conflict-of-interest issues. Many countries have special coastal management programs, but these focus mainly on fisheries conservation, leaving much to be desired as regards preservation of plant cover. Coastal conservation units exist in many parts of the world, but they are often effective on paper only. Here we present a description of the various types of plant communities that are found on sandy coastal plains and discuss the main environmental factors that influence the plants in these communities, what kinds of species are most common and how diverse are these communities, what is the geographic distribution of the majority of the species, and what are the most common threats to these habitats. But first we must define the landforms that underlie these coastal plain communities. 2. Landforms in Coastal Areas The vegetation which we will be dealing with in this chapter overlies a variety of landforms or substrate types. These landforms, plus the prevailing regional climate, greatly influence the plant communities and so it is important to understand more about them. Coasts are dynamic in nature, ever-changing because of a myriad of forces that act upon


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them. They are constantly evolving, and globally plate tectonics, or movements of the Earth’s crust, contribute greatly to these processes as do relative sea-level changes. Remember that in the not-so-distant past (some 18 000 years ago), sea level was 100 m or more below present levels, and that during more recent times (some 5 100 years ago), sea level was 4-8 m above its present level. So the coastline we know today has migrated over considerable distances, especially in areas of low declivity. Sea-level rise in these areas inundates beaches and swales, and on some coastlines, may totally erode beach ridges. Older landforms of Pleistocene age lying farther inland at higher topographic levels are sometimes spared from erosion by rising sea levels, being found in coastal areas even today. So, coastal plant communities overlie sediments that vary greatly in age. On low coasts, tides play an important role in coastal dynamics, as for example in the state of Amapá on the Brazilian coast. Here tidal amplitude is up to 12 m, one of the largest in the world. Another factor that influences coastline evolution is the sediment source, which may lie quite far inland (sediments brought to the shore by large rivers) or which may be close by (a broad continental shelf). Winds play an important role in the dynamics of coastal habitats, such as, for example, in forming waves that upon reaching the coast erode or rework the sandy sediments of the intertidal zone. Changes in coastlines are largely the result of changes in sediment supply. The sediment source may have disappeared, such as when replenishment from rivers is interrupted or when sediments from the continental shelf have been transported to dune fields. Man’s interference in coastal areas (attempts to “stabilize” the coastline, occupation of the narrow strip most affected by storms, etc.) also affects coastal processes and may cause the retention of sediments or the disappearance of the natural buffer strip that protects zones farther inland from storm surges. The most common sandy coastal deposits are beaches, beach ridges, dunes, and strand plains. Beach ridges are long sandy deposits that run parallel to the coastline, often isolating lagoons in areas of shallow coastal waters, whereas dunes consist of wind deposited sediments that lie atop the beach ridges or strand plains. Mobile dunes are often found near the beach, where wind action is more intense, while dunes stabilized by vegetation usually lie farther inland, behind the mobile dunes. 3. Vegetation Types and Community Structure As can be seen from the above, sandy coastal environments are characterized by environmental heterogeneity that is caused in part by geomorphological diversity. They are found on a variety of landforms and the plants that grow there are greatly influenced by oceanicity, that is, the influence that the ocean exerts on continental land masses. The resulting scenario is a mosaic of vegetation types. The best approach to presenting these vegetation types is perhaps along the natural gradient from the beach inland. Here we have not only a gradient of factors resulting from the presence of the ocean (e.g., salt spray, wind velocity), but also a temporal gradient in the age of the substrate, which increases in this direction. On broad coastal plains this gradient may not be continuous in a sea-inland direction due to the presence,


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today or in the past, of rivers, estuaries, lagoons, or other landforms. In this case, the sequence of natural accretion processes has been interrupted, as for example by the presence of a former river bed (paleocanal) that reveals where a river once cut through the sandy ridges to reach the sea, or by the nonalignment of these very ridges that reveals the presence of strong erosive action during sea-level oscillations. Near the ocean, plant communities on sandy deposits usually reveal a sharp zonation pattern subdivided into an outer pioneer zone and an inner dense coastal thicket. Plant communities farther inland do not necessarily follow a linear sequence across the dune field or strand plain. However, they are located along a gradient of increasing community complexity, that is, greater species richness and cover, taller stature, and greater biomass. 3.1. Beach Communities Beach vegetation is probably the best known of all the plant communities found on sandy shores. This vegetation grows on beaches all over the Tropics. Anyone who has ever walked along a sandy shore is familiar with the strand plants that grow on the shifting sands of the upper part of the beach. These plants form a dense cover on sheltered beaches where storm surges are uncommon and there is some degree of protection from strong winds. On unprotected beaches, subject to the full force of the waves and prevailing winds, the low shifting foredunes are only partially fixed by plants. In either case, this vegetation is inevitably washed by the sea at one time or another.

Figure 1. Strand vegetation reclaiming the beach after a storm surge; the dominant species is Ipomoea pes-caprae. Note the denser plant cover on a slight rise which was

not affected by the last storm surge. Northern coast of Rio de Janeiro, Brazil.


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The dominant species in this community are pioneer plants, that is, they are the first flowering plants to colonize the sand as it is deposited along the shore by wave action. They are called psammophytes because they prefer sandy substrates. Storm surges sometimes destroy these plants or bury them in sand, but as the storm abates, the beach profile becomes stable once more (even though it may be only for a short time), and long runners of Ipomoea pes-caprae or Sporobolus virginicus, two pantropical species, soon appear, advancing over the reworked sands towards the water’s edge (Figure 1). The physiognomy of beach vegetation is basically the same all over the Tropics. In the pioneer zone, plants must be able to take advantage of the new habitat that is made available for colonization on prograding coastlines. Low creeping plants usually form sparse cover on foredunes, increasing in density inland along a disturbance-inundation gradient. Many of these species are grasses, sedges, or creepers that have long, fast-growing stolons or rhizomes to keep pace with sand burial. In contrast, it is rare to find large woody species here because they usually do not tolerate wave disturbance and sand movement. Some plants also have succulent leaves and stems as a mechanism for water storage. This is the case of the beach scaevola (Scaevola plumieri), a low, pioneer plant from the Goodeniaceae family that inhabits beaches and dunes on the tropical shores of North America, South America and Africa. The seeds of this species roll down the slope of the beach from the dense clumps of Scaevola growing on the foredune crest and germinate in drift material. They are carried to other sites on the same beach or to other beaches, where the plant becomes established. Scaevola plumieri plays an important role in sand stabilization and foredune development because of the continuous growth of its stem and root system (Figure 2).

Figure 2. A foredune stabilized by Scaevola plumieri; Cabo Frio region, Brazil.


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Beach vegetation usually forms a very narrow strip on the upper beach of many coasts. However, in areas of low rainfall or where mobile dunes lie in a wide band next to the beach, the species found on the upper beach may penetrate as far as two kilometers inland. Landward of this stretch of creeping psammophytes on primary dunes we find a totally different vegetation type, and the boundary between these two types is usually quite sharp. Here, active sand interchange with the beach is nonexistent, over-wash frequency falls off sharply and disturbance from the sea is rare. This gives rise to a dense, stunted, sometimes thorny, thicket that defies human penetration. The vegetation is low towards the beach, gradually increasing in height inland and sometimes merging into a low forest (Figure 3). At first glance, the woody plants seem to have been neatly pruned. Wind is the factor here, together with salt spray, which kills off the shoots on the seaward-facing side of the thicket. In the Neotropics, cacti and bromeliads with thorny edged leaves are often common in this vegetation type, while some shrubs have sharp-pointed branch tips that contribute to the impenetrability of the woody barrier. The herb layer is usually quite sparse because the dense, shrubby canopy limits light penetration.

Figure 3. A preserved stretch of coastal plain vegetation in southern Rio de Janeiro state, Brazil, where rainfall is ca. 2000 mm annually. Note the wind-pruned aspect of

the woody vegetation. This vegetation type is common on the coast of Brazil and in many other parts of the world such as most of Africa, New Zealand, Australia, the gulf coast of the United States, Mexico and Central America. Some species are restricted to this narrow strip of vegetation even though they may have a wide distribution along the tropical coast. For example, Jacquinia armillaris


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from the Theophrastaceae occurs only in this narrow strip of coastal scrub and in saline areas near lagoons in Brazil, but it grows all along the tropical Brazilian coast, to northern South America, Central America, and the Caribbean. 3.2. Open Scrub Vegetation In many parts of the world, extensive areas of sandy coastal plains are covered by open scrub vegetation that may lie behind the coastal thicket described above or farther inland. The presence of this vegetation is closely related to the topography of the strand plain (Figure 4). Where series of abandoned parallel beach ridges alternate with depressions (swales) in a regular pattern, dry open scrub vegetation occurs at the higher elevations, that is, on the crest of the beach ridges, while wet open scrub lies in depressions. The beach ridges follow a chronological sequence of increasing age landward, the innermost ridges being older than those closer to the ocean. These can be dated when a sequence of aerial photographs is available. Open scrub vegetation also grows on partially stabilized dunes.

Figure 4. Aerial photo of a strand plain with (A) alternating series of long, parallel beach ridges with dry open scrub vegetation interspersed with (B) seasonally flooded

forests associated with lagoon arms and (C) wet open scrub occupying the swales. Northern coast of Rio de Janeiro state, Brazil (Photo scale - 1:8000).

The water table underlying dry open scrub vegetation is always several meters below the surface, and therefore the area is never flooded. Woody thickets of various sizes and


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shapes with sparse herbaceous undercover are scattered over the sandy substrate. The area between the islands of woody vegetation is occupied by a very sparse, mostly herbaceous cover, exposing a great deal of bare sand. In the Neotropics, it is common to see dense carpets of bromeliads in the herb layer underneath or on the edge of these thickets (Figure 5). Species of cacti and a geophyte palm (Allagoptera arenaria) are also present. Woody species dominate and vines are also common components of the vegetation islands because of high exposure to incident light. The shrubs support few vascular epiphytes, but in the denser, more humid patches, lichens and bryophytes are quite common.

Figure 5. A typical thicket of the open scrub vegetation with a dense layer of bromeliads (Vriesea neoglutinosa) underlying the 5-meter-tall Clusia hilariana shrubs; the stemless palm in the foreground is Allagoptera arenaria. Northern coast of Rio de Janeiro state,

Brazil. These vegetation islands often have one or more key species that facilitate (at least at a certain life-cycle stage) the arrival of other species, thus constituting a positive interaction between plant species. On Brazilian coastal plains, this may be a pioneer plant such as Allagoptera arenaria whose seeds germinate on the bare sand even when soil-surface temperatures reach 70oC. The leaves of this palm provide shade and reduce temperatures for other arriving species. Another key species in this region is Clusia hilariana (Clusiaceae) which germinates in the tank of a bromeliad (Aechmea nudicaulis). The young plant escapes from the tank when the outer bromeliad leaves die, and upon reaching a certain size favors the establishment of other species in this


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community. Positive interactions between species are especially important in structuring communities that occur in resource-poor environments, such as sandy coastal plains. The patchy organization of dry open scrub communities has intrigued researchers for years, raising questions as to the origin of vegetation islands. Some think this community is maintained by human interference (e.g., trampling by animals or vehicle use on the coastal plain, frequent fires), but a consensus has not yet been reached. Patchiness may be due to unequal distribution of soil nutrients or other habitat factors, or it may be an inherent characteristic of the vegetation itself. Studies of dry open scrub vegetation on strand plains in Brazil have shown that the processes of patch formation and evolution vary from one strand plain to the next. Open scrub vegetation grows on dunes, but vegetation structure is apparently quite different. A variety of species play the role of pioneers, resulting in functional model diversity.

Figure 6. A) Wet open scrub in the dry season; B) Water table floods low-lying open scrub after a heavy rain; C) Rusty colored water due to the presence of humic acids; D)

Thicket carpet of lichens growing under dense vegetation islands. Wet open scrub vegetation is found in low-lying areas that are subject to flooding during periods of heavy rainfall due to a rise in the water table. These areas may once have been lagoons; they often lie in the middle of the strand plain (see Figure 4), interrupting the continuity of ridges and swales. Here, the water table normally lies only about 50 cm below the soil surface. The water that drains from these areas is a rusty brown color, which reveals a build-up of peat deposits and high concentrations of humic acids (Figure 6). At higher topographic levels within these areas, open scrub vegetation is physiognomically similar to that described above; however, the area between the vegetation islands is covered by a dense herb layer. Even these areas are flooded briefly


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after a heavy rainfall. In lower lying areas where water-table levels are above-ground for most of the year, the shrubby vegetation is taller and denser, with a closed canopy.. Species composition varies along this gradient and termite mounds are common; it is common to find lichen species in the herb layer of more humid areas. Where flooding frequency is greater, the plant community is poorer in woody species, but richer in herbs. Bonnetia stricta (Theaceae), a low tree widely distributed in the Neotropics, is often monodominant in these areas. 3.3. Coastal Plain Forests The forests of these coastal plains are usually governed in structure, species diversity and composition by topography and, to a certain extent, by sediment age and soil salinity. Dune forests grow in areas where the water table is deep below the surface, while in wet areas such as the slacks between dunes or beach-ridge swales, there are seasonally flooded forests or sometimes permanently flooded forests (swamp forests). Well-developed dune forests are found on older beach ridges or on dunes that have been stable for a long time. Although these forests do not measure up in stature to most tropical rain forests, they often have high species diversity. The canopy is usually ca. 15-20 m above the forest floor, with some emergent trees growing to 25 m tall. This forest appears to have only one layer in the understory. Dense patches of bromeliads are common in the herbaceous layer. Seasonally flooded forests are found in swales between beach ridges, while permanently flooded forests are usually found near lagoon margins, on peat soils. Overall diversity in these forests, especially the swamp forest, is usually lower than that of dune forests due to the dominance of few species. Where the substrate is flooded for most of the year, the dominant tree species is often deciduous, allowing light to penetrate to the forest floor at certain times of the year. Here, dense layers of bromeliads provide viable germination sites for some tree species. 3.4. Dune Field Vegetation Dune fields deserve special mention here. As was seen above, dunes may overlie sand-based landforms such as beach ridges, but they are also built on top of other coastal landforms such as limestone cliffs (e.g., Africa) or clayey Tertiary deposits (Barreiras Formation - Brazil). The areal extent of these dune fields depends on ocean currents, climate, wind direction and frequency, and the topography immediately behind the beach. The plant species growing on dunes or in wet slacks between dunes are usually the same as those that occupy ridges and swales, but with varying abundance and spatial distribution. The herbaceous communities that occupy wet slacks, swales and lagoon margins are typical of marshes the world over, and are exceptionally rich in grasses and sedges. 4. Life forms Plants can be classified ecologically as well as taxonomically. This classification results in a series of different life forms. The life form spectrum of a given stand reflects the


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physiognomy of the vegetation, and life form spectra vary across a gradient of different vegetation types. It is important that we understand life forms because they are the structural components of vegetation and they also provide us with a way of understanding the plant’s relationship with the environment without identifying species using taxonomic nomenclature (a very difficult task, especially in tropical forests!). In the early 1900s, the Danish botanist Raunkiaer proposed a system of life forms that classified plants ecologically. This classification is based on a single trait that is related to the phenology and morphology of the species and that is important for the diagnosis of the plant’s strategy when faced with adverse climate or environmental conditions (e.g., fire). A graph of species frequency in relation to life form class is called a biological spectrum (Figure 7). Raunkiaer constructed life-form spectra for the world’s flora (known as Raunkiaer’s normal spectrum) as well as for different vegetation types worldwide. These spectra show a correlation between vegetation type and climate. For example, in deserts ca. 60% of the species are therophytes - plants that produce seeds annually and then die. This life form represents maximum escape strategy during adverse climate conditions (cold or dry season) since the species disappears from the habitat. Its regeneration module (embryo) is protected by a hard seed coat and awaits more favorable conditions to initiate the germination process and produce new plants. On the other hand, in tropical forests where the environment is much milder year round, phanerophytes (huge trees over 40 m tall to small woody plants ca. 1 m tall) predominate (65%). This life form represents a tolerance strategy, that is, the buds are exposed and the aerial part of the plant is present during more adverse conditions.

Figure 7. Life-form spectra of different biome types in Brazil: Restinga (sandy coastal plain) - Rio de Janeiro, Rain forest – Santa Catarina, High altitude grassland, Rio de


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Janeiro; and Raunkiaer’s normal spectrum; FAN – phanerophytes; CAM – Camephytes; HEM – Hemicryptophytes; GEO – Geophytes; TER – Therophytes

Sandy coastal plain (restinga) forests and shrubby vegetation behave like tropical rainforests, but the herbaceous communities have high percentages of geophytes and hemicryptophytes. The buds responsible for plant renewal in geophytes are hidden in the soil while in the case of hemicryptophytes, they are found at soil level, protected by the litter layer or by the leaf sheaths that have died and remained attached to the plant. This represents an escape strategy. Raunkiaer’s classification system is still used today because of its simplicity in comparing vegetation types that are made up of different species (from different environments, on different continents). However, this system does not consider the behavior of plants during the growing season and this has limited its use in tropical and subtropical climates where there often is no sharp distinction between seasons. Other systems have been proposed that use a number of attributes based on our knowledge of what role these traits play in the adaptation of plants to the environment and how they contribute to vegetation structure and physiognomy when viewed independently. In the past 15 years, the use of multiple attributes has been employed to recognize recurring patterns of traits in dominant species in studies in various parts of the world. This allows us to identify functional groups, that is, groups of plants that show similar response to environmental conditions and have similar effects on the main ecological processes, but are not necessarily related to one another. The search for these functional groups aims to reduce the complexity of plant species and their populations in order to create models that will predict how vegetation will respond to habitat disturbance and future climate changes. These models are expected to predict more precisely how species will respond when faced with environmental change. This will provide a basis for decision making concerning which species should be used in recovery and restoration of disturbed areas. For example, sandy coastal plain species have the ability to stabilize shifting dune sands so these species can be used to contain the sands of reject piles resulting from mining activities. Furthermore, since many of these species originally came from the Atlantic forest and colonized the more recent coastal plains, some can be used for the recovery of areas of this forest that have lost plant cover due to climate change. Which species should be used to this end will depend on how well we know their biology, the functional groups to which they belong and their role in ecological processes. 5. Species Diversity and Geography 5.1. Species Richness Sandy coastal plains are usually thought of as being rather poor in plant species. This notion is probably derived from our concept of the harsh beach environment or the sometimes rather sterile habitats of active sand dunes. But we must take into account that these sandy plains may also be occupied by full-fledged tropical forests that hold their own in species diversity when compared to contiguous montane forests. For


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example, a well-preserved beach ridge forest near Rio de Janeiro, Brazil, standing some 300 m from the ocean, was shown to have over 110 large tree species (Shannon´s index > 4.0), which compares favorably to species richness in neighboring low-montane Atlantic forests. These forests also have a rich understory of shrubs and herbs, and many epiphytes. Species richness, cover, stature and biomass of sandy coastal plain plant communities increase along a gradient from the sea inland. There is also increasing community complexity along this gradient, which may possibly be related to an increase in age of the substrate. Species richness of the vegetation types along a transect from the ocean to the innermost beach ridges in the Restinga de Jurubatiba National Park, located on a broad strand plain in Rio de Janeiro state, Brazil, is given in Table 1. The dune forest and the seasonally flooded forest are probably much richer in species than is evident from the data, for these forests have not yet been properly surveyed. The open scrub vegetation types have been quite thoroughly studied and this is reflected in the total number of species present. Habitat complexity in these two-phase plant communities probably contributes to species richness since the islands of woody vegetation create a number of different microhabitats (shaded interior, sunlit canopy, edge) in addition to the open, sparsely covered areas between the islands. The islands are especially rich in lianas. A comparison of species richness on a regional scale, from one sandy coastal plain to the next along the coast shows that overall richness varies greatly. This is due in part, of course, to the fact that the number of species is related to the size of the area and the areal extent of coastal plains varies widely. But habitat diversity also contributes to increased species richness. Coastal plains that are cut by rivers or have many lagoons and series of depressions between the beach ridges, or regions that are partially covered by dune fields tend to have higher species diversity. Historical factors may also enter into the picture, and former isolation events may have led to greater numbers of endemic species, which also contributes to overall species richness. 5.2. Geographic Distribution Plant communities by the sea tend to have a high percentage of cosmopolitan species. The foredune plant community, for example, near the beach (pioneer zone) is characterized by widely distributed species and genera. These plants occur on beaches all over the tropics and are said to have a pantropical distribution. Common species that show this wide distribution are the creepers Ipomoea pes-caprae, Sporobolus virginicus, Remirea maritima and the succulent shrub Scaevola plumieri. The grasses and sedges found in the wet slacks between dunes and beach ridges also tend to have a widespread distribution. Another group of species that shows a relatively ample geographic range in coastal areas includes those tolerant of relatively high levels of soil salinity, species that occupy beaches but also find a suitable habitat in the transition zone between dunes and saline areas (mangroves, salt flats). Species in this group that tend to extend over several degrees of latitude along the South American coast are Chrysobalanus icaco (beach plum), Dalbergia ecastophyllum (coin vine) and Jacquinia armillaris.


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In the plant communities further from the beach, where factors such as inundation by seawater, salt spray, and wind speed and frequency are attenuated, the vegetation consists of species that often have more restricted distributions. Many forest species are restricted to coastal plain forests and to the vegetation type that lies closest to the coastal plain. For example, in eastern Brazil, tree species endemic to the coastal plain forests are quite rare, most species being found also in the contiguous Atlantic forest. In fact, overall species composition of the coastal plain vegetation is highly influenced by the neighboring vegetation type, with about 80% of the species occurring also in the contiguous Atlantic rain forest. Species endemism is rather low in these coastal plain communities, suggesting that there has not been enough time for speciation after the geologically younger coastal plains were occupied by Atlantic forest species. 6. Conservation Coastal areas have a long history of human habitation. In eastern South Africa, human settlements on the coast date to 4 A.D. Early inhabitants were attracted to the coast by freshwater sources and abundant food. In the New World, we have some notion of how tribal groups lived in coastal areas due to the presence of shell mounds, that is, sites where there are accumulations of shells and the bones of animals that were eaten by these people, as well as evidence of hearth fires. The vegetation surrounding these areas often contains an abundance of plant species that have a history of use by man. Therefore, coastal vegetation most certainly has a long history of exploitation. In arid and semi-arid regions of the Old World, coastal areas are still used by man for sustenance. Range livestock (sheep, goats, camels, donkeys) is a traditional method of land use, causing a tremendous impact on the vegetation through over-grazing and trampling. In areas where a fragile herb layer protects sandy sediments, such intensive use causes erosion and the activation of once stable dunes. Valuable mineral resources are often found in sandy coastal areas. Dunes are mined for heavy metals (e.g., ilmenite, rutile, zircon) and diamonds. Dune quarries supply sand for construction and cement manufacture. Intense disturbance by these activities often destroys the vegetation completely. Strip mining for diamonds in Namibia removes the soil, exposing the old rocky sea bed. Oil spills at sea may reach the coast, causing severe damage to wildlife and polluting pristine areas. In other places, the vegetation itself is the target of exploitation. It is the source of fuel-wood and charcoal. Some coastal species were once harvested for their valuable dyes (Brazilwood – Caesalpinia echinata; Logwood - Haematoxylum campechianum). Wildlife habitats are destroyed as beach ridges and dunes are cleared for planting coconut palms, cassava, groundnuts, okra and pineapple. Grass is often planted under the palms to serve as pasture for cattle, and wetlands are drained, killing off forests. Since the 1970s, man has come to regard the seashore as a prime vacation spot. In Brazil, for example, where the country’s largest cities are located along the coast due to its colonization history, there is pressure from a growing population that wants to vacation in areas outside the city. Summer homes and seaside resorts have had a


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tremendous impact on the vegetation of beaches and sandy coastal plains. Unfortunately, governments often provide incentives for developing these areas. Natural processes also take their toll on coastal plant communities. The first obstacle encountered by hurricanes when they make landfall is beach and coastal vegetation. The predicted rise in sea level resulting from climate change will have a huge effect on coastal communities, as it has in the past. So what is a tract of coastal vegetation worth? It provides protection against storm surges, forming a buffer that helps to protect adjacent farmland or urban areas. It reduces beach erosion and aids in groundwater replacement. It provides a backdrop for recreational activities and ecotourism. And it contains a myriad of plant species that are used by traditional fishing communities, among other uses, that can only survive in a natural setting. In the late 20th century, conservation efforts were focused on plant inventories, preserving rare species from extinction and maintaining the habitats of as many species as possible. Today, attention is more sharply focused on understanding the physical and ecological processes that take place in these habitats. Sustainable use of coastal areas will depend largely on involving local communities and governments in the decision-making process so as to effectively manage these areas to the satisfaction of all users. Glossary Beach ridge: Elongate sandy deposit formed by storm waves and currents,

parallel to the shoreline, separated from each other by shallow depressions.

Biodiversity: The variety of life at three different levels: genetic diversity; species diversity; and ecosystem diversity.

Chamaephyte: Low-growing perennial plants having renewal buds at or just above ground level (50 cm).

Creeper: A plant that spreads along the surface of the ground. Dunes: Sandy elevations formed by sediments transported by the wind. Endemic: Native to, and restricted to a particular geographical region. Flora: The plant life of a given region. Geomorphology: The study of the characteristics, origin and development of the

surface features of the earth Geophyte: A perennial plant having renewal buds buried well below the

soil surface. Habitat: The locality, site and particular type of local environment

occupied by an organism. Halophyte: A plant living in saline conditions. Hemicryptophyte: A perennial plant with renewal buds at ground level or within

the surface layer of the soil. Holocene: A geologic epoch within the Quaternary period (ca. 10 000 years

B.P. to the present time). Intertidal zone: The shore zone between the highest and lowest tides. Neotropics: The tropical region of the New World. Oceanicity: The influence of the ocean on continental land masses.


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Pantropical: Widespread throughout tropical regions of the world. Physiognomy: The characteristic features or appearance of a plant community

or vegetation. Pioneer species: The first species to colonize a barren or disturbed area. Pleistocene: A geologic epoch within the Quaternary period (ca. 1 600 000

years B.P. to 10,000 years B.P.). Prograding coast: A coastal region where the shoreline is advancing toward the

ocean. Prostrate: A plant with stems that lie flat on the ground. Psammophyte: A plant growing in unconsolidated sand. Retrograding coast: A coastal region where the shoreline is retreating. Rhizome: A horizontal underground stem. Scrub: A vegetation type consisting of low trees and shrubs. Shannon’s index: a diversity index that takes into account the number of

individuals as well as the number of species. Species diversity: Relative species abundance in a given locality. Species richness: The absolute number of species in an assemblage or community. Stolon: An elongate, horizontal stem that grows along the ground and

roots at the nodes or at the tips, giving rise to a new plant. Strand plant: A plant growing on the shore immediately above high tide level. Strand plain: A series of ridges typically associated with and parallel to a

beach forming a coastal plain. Swale: A long, narrow, usually shallow trough between beach ridges. Thicket: A dense vegetation type with continuous canopy consisting of

shrubs and small trees. Upwelling: A phenomenon of coastal regions where cold, heavy, deep water

laden with nutrients flows upward as warm surface water is drawn away by offshore currents.

Vegetation: The total plant life or cover in an area. Zonation: The distribution of organisms in distinctive areas, layers or

zones. Bibliography Martinez M.L. & N.P.Psuty (eds.) (2004). Coastal dunes: ecology and conservation. 386 pp. Berlin: Springer-Verlag. (Ecological Studies 171.) [This text is a basic compendium of current knowledge on coastal dunes in various parts of the world.]

Rocha C.F.D., F.A.Esteves & F.R.Scarano (orgs.). (2004). 374 pp. Pesquisas de longa duração na Restinga de Jurubatiba: ecologia, história natural e conservação. São Carlos: RiMa. [This text summarizes a number of seminal studies on sandy coastal plain vegetation in the southeast region of Brazil.]

Scarano, F.R. (2002). Structure, function and floristic relationships of plant communities in stressful habitats marginal to the Brazilian Atlantic Rainforest. Annals of Botany 90: 517-524. [This paper discusses Atlantic coastal vegetation as a complex series, focusing on the positive interactions among plants in communities that are marginal to this Atlantic forest]

Seeliger, U. (ed.) (1992). Coastal plant communities of Latin America. 392 pp. New York: Academic Press. [This text provides descriptions of the most common coastal plant communities found in Latin America.]

Van der Maarel E. (1993). Dry Coastal Ecosystems: Africa, America, Asia and Oceania. 616 pp.


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Amsterdam: Elsevier. (Ecosystems of the World 2B.) [This text discusses the ecology of all types of coastal ecosystems.] Biographical Sketches Dorothy Sue Dunn de Araujo teaches Plant Ecology in the Ecology Department and gives a course in Methods for Sampling Vegetation for graduate students at Rio de Janeiro Federal University. Her interests are plant ecology and biogeography, especially structure and composition of coastal vegetation, patterns of species distribution, and conservation. Miriam Cristina Alvarez Pereira has taught Economic Botany in the Botany Department at Rio de Janeiro Federal University. Most of her field research has been done in protected areas of Brazil such as Serra do Cipó National Park in Minas Gerais and Restinga de Jurubatiba National Park in Rio de Janeiro. She is presently an Associate Researcher at the Rio de Janeiro Botanical Garden Research Institute, involved in field work in the Cabo Frio Center of Plant Diversity. Her main areas of research are plant ecology, vegetation structure and functional groups.


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