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The greater part of the west coast of South America (5°00'-29°55'S) is occupied by the Peruvian and Atacama deserts, which form a continuous belt for more than 3500 km along the western escarpment of the Andes from northern Peru to northern Chile. The phytogeography and ecology of these deserts have been reviewed in detail (Rauh 1985; Rundel et al. 1991), and a floristic inventory of the entire area has been completed (Dillon, in prep. for publication). While desert is continuous from Peru to Chile, the topography, climate and vegetation of each of the deserts is distinct (Rundel et al. 1991; Duncan and Dillon 1991). The Peruvian Desert is presented here; for the Atacama Desert, see the separate Data Sheet (CPD Site SA43).
The Peruvian Desert is a narrow band of hyper-arid habitat confined to the western coast and extends over 2000 km (5°-18°S), covering c. 140,000 km² or 11% of Peru (Library of Congress 1979). Three climatic anomalies are largely responsible for development of the hyper-arid conditions along the west coast of South America (Trewartha 1961; Johnson 1976).
There is remarkable homogeneity of temperature along the entire latitudinal extent of the desert. This pattern of temperature stability results from the influence of cool sea-surface temperatures associated with the northward flow of the coastal Humboldt (Peruvian) Current.
Since the extreme conditions exist for such an extended latitudinal distance (c. 3500 km), there are relatively abrupt climatic transitions both to the north and the south. As a result, a steppe climate is poorly developed along those margins.
Brief periods of heavy rainfall and relatively high temperatures occasionally affect parts of the desert, bringing wet tropical conditions. These periods are associated with rare yet recurrent proximity to the continent of the oceanic current El Niño (Dillon 1985a, 1985b; Dillon and Rundel 1989; Quinn, Neal and Antúnez de Mayolo 1987; Caviedes 1975).
Important also is the influence of strong atmospheric subsidence associated with a positionally stable, subtropical anticyclone. The result of the several factors is a mild, uniform coastal climate with regular formation of thick stratus cloud banks below 1000 m during the winter months (Prohaska 1973). Where coastal topography is low and flat, this stratus layer dissipates inward over broad areas with little biological effect, but where isolated mountains or steep coastal slopes intercept the clouds, a fog zone develops with a stratus layer concentrated against the hillsides.
These fogs, termed "garúas" in Peru and "camanchacas" in Chile, are the key to the extent and diversity of vegetation throughout the deserts of the western coast. The moisture allows the development of fog-zone plant communities termed "lomas" (small hills) between sea-level and 1000 m. Other authors have referred to these plant formations as the fertile belt (Johnston 1929), fog oases (Ellenberg 1959) or meadows on the desert (Goodspeed 1961; Goodspeed and Stork 1955). In Peru, there exist over 40 discrete localities in the desert that support vegetation (Map 77), including offshore islands such as Las Viejas, San Gallán and San Lorenzo. The actual area covered by vegetation, even during periods of optimal weather and maximum development, is probably less than 2000 km².
Lomas formations occur as discrete communities or islands of vegetation separated by hyper-arid territory devoid of plant life. Since growth is dependent upon available moisture, climatic patterns determine plant distributions. Topography and substrate combine to influence patterns of moisture availability and the area of suitable habitat. Ecological requirements and tolerances of individual species ultimately determine community composition; species endemism exceeds 40% (Rundel et al. 1991). This account provides brief descriptions of the larger lomas formations, with data on species diversity where available.
The geomorphology of north-western Peru consists of a broad coastal plain extending from the Ecuadorian border to near Casma (9°28'S). Some of this region has been geologically uplifted (Robinson 1964), but only a few areas are above 1000 m (cf. CPD Site SA41). Although the coastal fog zone only extends from 0-500 (-800) m in northern Peru (Rauh 1958), the low topography provides a broad arid zone, much of it without vegetation. Low shrubs dominate the sparse vegetation below 100 m, and cacti increase in importance with higher elevation. An interior desert at intermediate elevations is absent from northern Peru, unlike central and southern Peru.
North of 6°S, the prevailing current turns west to the open ocean; Clüsener and Breckle (1987) report small coastal stands of Avicennia germinans at 5°30'S near the mouth of the Piura River, and Rhizophora mangle (R. harrisonii) at 3°44'S near Bocapán. The vegetation of the Tumbes region (near Ecuador) has been described by Ferreyra (1957).
Much of the northern coastal plain (5°-7°S) is covered by the semi-arid Sechura Desert, with extensive areas of flat sandy plains and active dunes (Silbitol and Ericksen 1953; Kinzl 1958; Broggi 1961). Large expanses support little or no vegetation; sometimes Parkinsonia aculeata and the narrow endemic Alternanthera peruviana are common. A brief description of vegetation in the area of Cerro Illescas along the coast near Bayóvar (5°50'S) has been given by Ferreyra (1979) and Huey (1979). Flat sandy terrain is relatively bare, whereas low hummocky dunes are stabilized by Capparis scabrida and C. avicenniifolia. Dunes along the immediate coast are stabilized by Distichlis spicata and Cryptocarpus pyriformis (Weberbauer 1911).
River valleys flowing through the southern Sechura Desert are now largely irrigated agricultural land but once supported riparian communities with thickets of Acacia macracantha, Salix humboldtiana, Schinus molle, Sapindus saponaria, Muntingia calabura and a variety of woody and semi-woody shrubs (Weberbauer 1911; Ferreyra 1983).
Inland from the Sechura Desert along the coastal plain of northern Peru, semi-desert vegetation is well developed on slopes between the ranges of the Andes. Weberbauer (1911) and Ferreyra (1979, 1983) described this vegetation, which has dwarf trees of Eriotheca discolor, Bursera graveolens and Acacia huarango, a diversity of columnar cacti, and terrestrial bromeliads. The phytogeographical significance of these woodlands has been discussed by several botanists (Weberbauer 1936; Ferreyra 1960; Simpson 1975; Dillon and Cadle 1991).
Cerro Reque (6°52'S, 80 spp.), a small mountain near Chiclayo, marks the most northern extension of typical lomas vegetation (Llatas, unpublished data), including the narrow endemic Sisymbrium llatasii. North-west of Trujillo, Cerro Campana (7°58'S, 185 spp.) and Cerro Cabezón (7°54'S, 120 spp.) are the northernmost extension of well-developed lomas vegetation. On the lower sandy slopes below 200 m occurs a Tillandsia zone with a mixture of cacti (Espostoa melanostele, Haageocereus decumbens, Melocactus trujilloensis), small trees and prostrate shrubs. Above 400 m, moisture conditions are more favourable and a diverse community of shrubs and herbaceous perennials occurs. These include several species not usually found within coastal desert environments which are present in large numbers, such as Tillandsia multiflora, Puya ferruginea, Hypericum uliginosum, Pelexia matucanensis, Peperomia dolabriformis and Valeriana pinnatifida. Endemic species from this region include Pitcairnia lopezii - the only member of this large genus to occur in the lomas formations, and Senecio truxillensis, Apodanthera ferreyrana, Matelea alicae and Solanum mochiquense (Sagástegui, Mostacero and López 1988).
To the south continues a series of small discrete mountains within the coastal plain, each with vegetation between 200-600 m, including Cerro Prieto (7°59'S, 30 spp.); Cerro Cabras (8°03'S, 48 spp.); Cerro Chiputur (8°10'S, 95 spp.); Cerro Negro (8°18'S, 26 spp.); and Lomas de Virú (8°19'S). These extensively studied formations (Sagástegui, Mostacero and López 1988) are a mixture of shrubs and herbaceous species similar to the composition on Cerro Campana. At Cerro Chimbote (9°04'S, 10 spp.) and Casma (9°28'S, 25 spp.), near where the coastal plain becomes narrow, is less lomas vegetation than the well-developed formation on Lomas de Lupín (10°33'S, 57 spp.). The lower-elevation lomas zone is dominated by cryptogams (Ferreyra 1953) and no endemics are recorded.
Perhaps the most famous lomas formation in Peru is the Lomas de Lachay (picture) (11°21'S, 100 spp.), c. 60 km north of Lima; this site is a National Reserve. This formation was described glowingly and in detail by Ruiz in the late 18th century (see Jaramillo-Arango 1952). Ferreyra (1953) recognized two distinctive lomas zones here. The lower zone (100-300 m) is dominated by a cryptogamic community of Nostoc commune and a diverse array of foliose and fruticose lichens. Herbaceous and semi-woody vascular plants are less common. The perennial vegetation becomes much richer above 300 m, where distinctive communities occur on hillsides or rocky slopes in canyons. Dry rocky slopes support stands of terrestrial bromeliads (Tillandsia latifolia, Puya ferruginea) and lichens. Moist micro-habitats on these slopes support a very different flora with many herbaceous perennials. Canyons and valleys in the lomas zone are characterized by relatively dense stands of small trees, notably Caesalpinia spinosa, Capparis prisca, Senna birostris and Carica candicans. A remarkable feature of these small woods is the dense accumulation of epiphytes of all types - mosses, lichens, ferns, Peperomia hillii, Calceolaria pinnata and Begonia geranifolia are common on branches and trunks of the low trees.
Directly to the south, the Lomas de Chancay and Iguanil (11°24'S, 77 spp.) comprise a rich fertile zone between 160-400 m (Ferreyra 1953). True succulents are less common and a diverse group of herbaceous species and shrubby perennials dominate. The Lomas de Pasamayo (11°38'S, 20 spp.) occupies the upper limit of a large bluff affronting the ocean at nearly 500 m. This small herbaceous community includes Loasa urens, Solanum multifidum, Palaua moschata, Erigeron leptorhizon, Acmella alba, Nolana gayana, N. humifusa, Verbena litoralis and Cryptantha limensis.
The city of Lima is situated where the Rimac and Chillón rivers merge; from Lima southward, frequency and amplitude of precipitation decrease significantly and the lomas communities have lower overall diversity. South of Lima, the Lomas de Amancaes (12°01'S, 50 spp.), Atocongo (12°08'S, 80 spp.) and Lomas de Lurín (12°17'S, 30 spp.) support varied communities (Ocrospoma-Jara 1990; Cuya and Sánchez 1991).
Three of the guano islands offshore from the central Peruvian coast (San Lorenzo, San Gallán, Las Viejas) are high enough to support sparse lomas communities. Johnston (1931) recorded only 19 species of vascular plants on these islands, including one endemic - Nolana insularis (Johnston 1936; Ferreyra 1961b). Between Lima and Cañete (13°05'S), the coastal plain disappears and coastal geomorphology is dominated by the foothills of the Cordillera Occidental of the Andes. Ridges of these foothills separate numerous river valleys that drain the Andes in this region. Geological evidence suggests past land subsidence, with broad valley floors restricted to a few small coastal areas (Robinson 1964). A broad coastal plain extends from around Pisco to just north of Atiquipa.
Steep coastal ridges with a series of marine terraces are present from the Paracas Peninsula near Pisco to south of Ica (Craig and Psuty 1968). Inland from these ridges the coastal plain lies largely below 300 m, though individual terraces occur up to 700 m (Robinson 1964). The sparse vegetation of the Lomas de Amara (13°42'S) and adjacent communities near Pisco and Ica have been described by Craig and Psuty (1968) and several government reports (ONERN 1971b, 1971c).
Above the lomas communities, Neoraimondia arequipensis forms a characteristic belt of columnar cacti of low density. As at Nazca (14°50'S), extensive stands of Acacia macracantha, Prosopis chilensis and other phreatophytes (with very long roots to reach the water table) are present along the channels of the Pisco and Ica rivers. Scattered stands of cultivated date palms (Phoenix dactylifera) suggest a dependable supply of groundwater. Marshy soils are present below the fog zone along the coast, with saline areas dominated by Distichlis spicata and freshwater sites supporting stands of Scirpus. Weakly developed dunes adjacent to the coast are frequently stabilized by Distichlis and Sesuvium portulacastrum, a succulent halophyte. Distichlis is a particularly effective stabilizer since its roots extend several meters deep (Craig and Psuty 1968).
Lomas vegetation is not well developed inland around Nazca, but extensive riparian forests of Prosopis chilensis and Acacia macracantha are present in river channels from near the coast up to 2000 m (ONERN 1971a). Other important riparian species include Salix humboldtiana and Arundo donax, as well as a variety of low shrubs and herbaceous plants. About 12 km south of Nazca, a small population of Bulnesia retama represents an unusual disjunction from populations in central Argentina (Weberbauer 1939).
Near the port of Lomas, the Lomas de Jahuay (15°22'S, 63 spp.) are found on windy flats at 300-900 m, and include several southern Peruvian endemics such as Nolana plicata, Modiolastrum sandemanii, Coursetia weberbaueri, Malesherbia angustisecta, Nolana tomentella and Ambrosia dentata.
The Lomas de Atiquipa (15°48'S, 120 spp.) and Chala (15°53'S, 20 spp.) in the northern part of the Department of Arequipa form a continuous formation broken only by a broad dry river channel. These were studied early and intensively by Peruvian botanists because of their rich diversity, and include Arcytophyllum thymifolia, Calceolaria ajugoides, Galvezia fruticosa, Encelia canescens, Neoporteria islayensis (Islaya paucispina), Senna brongniartii, Heterosperma ferreyrii, Nolana inflata, Croton alnifolius, Heliotropium pilosum, Senecio smithianus and the narrow endemic Astragalus neobarnebyanus (Gómez-Sosa 1986). This marks the northernmost station for the predominantly Chilean Argylia radiata. Inland to the north-east of Chala, the Lomas de Cháparra (Taimara) (15°50'S, 36 spp.) contain relict stands of small trees to 5 m tall occupying ravines at upper elevations, including Maytenus octogona, Caesalpinia spinosa and the endangered endemic Myrcianthes ferreyrae, which has been reduced to a few hundred individuals at a handful of local sites.
North of Camaná, the maritime slopes of an arm of the Andes extend near the coast and break up the coastal plain. The Lomas de Atico (16°14'S, 67 spp.) and Ocoña (16°30'S, 14 spp.) contain sparsely distributed shrubs such as Coursetia weberbaueri and herbaceous species including Nolana spathulata, N. pallida, N. mariarosae and Sesuvium portulacastrum. South of Atico a sizeable population of Neoraimondia aticensis occurs near the ocean, with Heliotropium krauseanum, Calandrinia paniculata, Cleistocactus sextonianus (Loxanthocereus aticensis) and the endemics Eremocharis ferreyrae, Domeykoa amplexicaulis, Helogyne hutchinsonii, Nolana aticoana, Mathewsia peruviana and Hoffmanseggia arequipensis.
Lomas south of the city of Camaná (16°35'S, 83 spp.) are well developed where the loose sandy soils are bathed by fog, and form a primarily herbaceous community from 20-800 m. The most common species is Eragrostis peruviana, which in 1983 because of a strong El Niño formed large pure communities. Other common herbaceous species include Tiquilia paronychioides, Pasithea coerulea, Atriplex rotundifolia, Geranium limae, Cenchrus humilis, Astragalus triflorus, Loasa urens and Cristaria multifida, as well as Cleistocactus sextonianus (Loxanthocereus camanaensis) and the narrow endemics Palaua camanensis, P. trisepala and Nolana cerrateana.
The Lomas de Mollendo (16°55'S, 122 spp.) and Islay, 20 km north of Mejía, support a large and diverse flora (Péfaur 1982). The community extends from 150 m to c. 1100 m in elevation within a narrow quebrada. On the slopes near the ocean frequent species include Frankenia chilensis, Spergularia congestifolia, Verbena (Glandularia) clavata and the narrow endemic Viguiera weberbaueri. At higher elevations are numerous woody species (Carica candicans, Calliandra prostrata, Gaya pilosa, Lycium stenophyllum, Nolana pilosa, Monnina weberbaueri) and annuals and perennials [Alstroemeria paupercula, Lupinus mollendoensis, Caesalpinia (Hoffmanseggia) miranda, Polyachyrus annuus and Ophryosporus hoppii]. Vegetation ceases near 1100 m - well above the fog zone. To the east, toward the Andean Cordillera, stretches the hyper-arid Pampa del Sacramento, an area of extensive sand dunes virtually devoid of vegetation (Barclay 1917; Finkel 1959). Similar formations are also found immediately to the north (Gay 1962).
Extensive lomas reappear at Mejía (17°07'S, 62 spp.) where lomas vegetation occurs sporadically on low sandy hills up to 600 m and more extensively on the higher hills farther inland to 1000 m. Along the coast, perennial halophytic endemics such as Nolana adansonii, N. thinophila and Tiquilia conspicua are common along the beaches. On slopes between 200-600 m, a herbaceous community includes Palaua velutina, Portulaca pilosissima and Weberbauerella brongniartioides. At elevations above 600 m occasional cacti are encountered, including Neoraimondia arequipensis and the night-blooming Haageocereus decumbens (H. australis). From 800-1000 m, nearly continuous grasses and perennial herbs occupy the slopes, including several rare species such as Centaurium lomae, Microcala quadrangularis and Sisyrinchium micrantha. Woody species include the small tree Caesalpinia spinosa, a montane species common to lomas formations of central Peru. Some 20 km to the interior north, the Lomas de Cachendo (17°00'S, 20 spp.) receive sufficient fog to develop a small community including Palaua dissecta, Eragrostis peruviana, Oxalis megalorhiza and occasionally Neoraimondia arequipensis.
The pattern of dominance by herbaceous species is broken in the coastal Lomas de Mostazal near the port of Ilo (17°45'S, 53 spp.). Rich herbaceous communities similar to those described above frequently cover the entire ground surface, yet in addition a shrub community dominated by Croton alnifolius and Grindelia glutinosa occurs. During 1983 there were vast numbers of Palaua weberbaueri, P. dissecta, Urocarpidium peruvianum, Nolana pallidula and N. spathulata. East of these formations, large colonies of Tillandsia purpurea cover the sand dunes.
North-east of Tacna, slightly rolling hillsides (200-672 m) near Sama Grande and Sama Morro (17°48'-17°50'S, 100 spp.) support a flora first inventoried by Ferreyra (1961a). Rich herbaceous communities develop in response to sufficient fog or rare aperiodic rains. During the strong El Niño event of 1982-1983, dense mixed communities of annuals and herbaceous perennials developed, including Nolana spathulata, N. arenicola, N. gracillima, Portulaca pilosissima, Calandrinia paniculata, Cristaria multifida, Eragrostis weberbaueri, Argylia radiata, Leptoglossis darcyana, Allionia incarnata, Tiquilia litoralis, Palaua dissecta, P. pusilla, Caesalpinia (Hoffmanseggia) prostrata, Mirabilis elegans and Monnina weberbaueri. Woody species included Ephedra americana, Encelia canescens and the suffrutescent Chenopodium petiolare, Nolana confinis, N. lycioides and Senna brongniartii. The endemic cactus group Islaya of Neoporteria sensu lato has its southernmost species in this region Neoporteria krainziana (I. krainziana).
Current estimates (Dillon, unpublished) for the total number of species represented within the Peruvian lomas formations are 72 families, 284 genera, 557 species; total numbers within the Atacama formations are 80 families, 225 genera, 550 species. Of the total of nearly 1000 species, only 68 species (c. 7%) are distributed within both the Peruvian and Chilean formations. The families containing the greatest diversity throughout the Peruvian and Atacama deserts include Asteraceae (57 genera, 147 spp.); Cactaceae (c. 14 genera, c. 92 spp.); Nolanaceae (2 genera, 79 spp.); Leguminosae (26 genera, 71 spp.); Solanaceae (19 genera, 64 spp.); Malvaceae (9 genera, 56 spp.); Apiaceae (13 genera, 51 spp.); and Boraginaceae (7 genera, 51 spp.).
The lomas species can be grouped into five broad categories (Dillon 1989): (1) wide-ranging pantropical or weedy species found within and outside the lomas (Müller 1988); (2) amphitropic disjuncts, primarily from arid and semi-arid regions of North America; (3) lomas disjuncts from adjacent Andean source populations; (4) lomas endemics (Peruvian and Chilean) with no extra-lomas populations, but widely distributed within the lomas; and (5) narrow lomas endemics found in only one or a few lomas formations.
While the arid environment is continuous between Peru and Chile, there seems to be a significant climatic barrier to dispersal between 18° and 22°S latitude in extreme northern Chile. The lack of topographic barriers to provide fog in the region between Arica and Antofagasta produces conditions with drought too severe for most plants to survive. Less than 7% of the combined Peruvian and Chilean lomas flora occur on both sides of this zone (Duncan and Dillon 1991). The four most important groups of coastal Peruvian cacti (Haageocereus, Neoraimondia, the Islaya group of Neoporteria, the Loxanthocereus group of Cleistocactus) do not occur south of Arica. Conversely, three of the most important cactus groups of northern Chile (Eulychnia, Copiapoa, Neoporteria sensu stricto) fail to cross into Peru (Rauh 1958). Terrestrial Tillandsia species, which are a dominant aspect of the coastal vegetation of southern Peru, are of very limited distribution in the Atacama; the southernmost limit of the terrestrials is between Iquique and Tocopilla where pure stands of Tillandsia landbeckii occur.
Nolana occurs from central Chile to northern Peru and the Galápagos Islands, with peaks of species diversity near Paposo in Chile and Mollendo in Peru, but only Nolana lycioides is distributed both in Chile and Peru. A number of genera containing coastal perennials have crossed this floristic barrier in the zone south of Arica, including Alternanthera, Ophryosporus, Tetragonia, Oxalis, Calandrinia, Senna, Palaua, Tiquilia, Heliotropium, Caesalpinia, Tephrocactus sensu lato and Urocarpidium.
Despite the barrier, a number of species have become successfully established over the entire length of the Peruvian and Atacama deserts, such as Apium (Ciclospermum) laciniatum, Encelia canescens, Chenopodium petiolare, Mirabilis prostrata and Loasa urens. Alstroemeria paupercula occurs from Caldera in Chile to Chala in south-central Peru. Pasithea coerulea and Fortunatia biflora occur from central Chile to southern Peru.
Although many of the Peruvian and Atacama desert species have obvious floristic affinities with the Andean Cordillera, the level of endemism in the isolated coastal vegetation is extremely high for some families, e.g. Bromeliaceae, Cactaceae, Malvaceae, Aizoaceae, Portulacaceae, Solanaceae and Poaceae. Two endemic families of Andean flora, the Nolanaceae and Malesherbiaceae, are largely Atacama/Peruvian desert groups (Solbrig 1976). Most of the important desert families, however, are widespread: Apiaceae, Asteraceae, Boraginaceae, Cruciferae and Leguminosae.
The most endemic genera are to be found in southern Peru between 15°-18°S, and in northern Atacama formations, specifically between 24°14'-26°21'S. These include the largely Peruvian genera Mathewsia and Dictyophragmus (Cruciferae) and Weberbaueriella (Leguminosae), and the largely Chilean genera Copiapoa and Eulychnia (Cactaceae), Dinemandra (Malpighiaceae), Domeykoa and Gymnophyton (Apiaceae) and Gypothamnium and Oxyphyllum (Asteraceae). A considerable number of endemics occur within a wide range of genera, including species of Ambrosia, Argylia, Astragalus, Nolana, Calceolaria, Palaua, Cristaria, Tiquilia, Dinemandra and Eremocharis. Müller (1985) calculated 42% overall endemism within the Peruvian lomas formations, with 62% endemism for southern Peru and 22% for central Peru.
In contrast, in northern Peru between 8°S and 12°S occurs the greatest number of species with coastal disjunct populations and principally Andean distributions. In this region, various families with typically more mesic requirements are represented -e.g. Orchidaceae, Passifloraceae, Piperaceae and Begoniaceae.
A few North American species with amphitropic disjunct distributions are present in the lomas formations. For the most part these are not the usual Mediterranean-climate species commonly disjunct from California, U.S.A. to central Chile (Constance 1963; Raven 1963, 1972). Rather, the species have their origins in the Sonora or Mojave deserts and their distributions are often restricted to the lomas formations. Also several primarily North American genera have endemic species within the coastal deserts, including Ambrosia dentata, Encelia canescens, Viguiera weberbaueri and several species of Tiquilia. Other primarily North American taxa represented within the Peruvian and/or Atacama deserts include Nama dichotoma, Phyla nodiflora, Linaria canadensis, Microcala quadrangularis, Triodanis perfoliata, Cressa truxillensis, Malacothrix clevelandii, Bahia ambrosioides, Amblyopappus pusillus and Perityle emoryi.
A few taxa are derived from other arid regions of the world. For example, the widespread succulents Carpobrotus chilensis and Mesembryanthemum crystallinum likely have origins in South Africa.
Archaeologists have evidence that indigenous peoples have used the lomas formations as a temporal resource for over 5000 years (Moseley, Feldman and Ortloff 1981); in their original state, the lomas provided essential sites for foraging and the periodic cultivation of crops. No sustainable agriculture is currently conducted within the lomas formations.
As opportunities for genetic engineering expand, many taxa within the lomas formations will be sources of germplasm for agriculture and horticulture. For example, the economically important genera Solanum and Lycopersicon contain several lomas endemics with potentially useful ecophysiological characteristics (Hanson, pers. comm.).
Social and environmental values
The intrinsic value of the lomas formations is the unique nature of their composition and their high levels of endemism. The fauna of the lomas has not been studied in detail, but is potentially as rich in endemics as the flora. For these reasons, the lomas formations provide opportunities for scientific research and ecotourism. The Reserva Nacional de Lachay is one example of the successful management of a lomas formation, while providing recreational opportunities. If the impact on delicate communities is controlled through supervision, other lomas formations can be preserved for the future while being enjoyed by the public especially the striking display resulting from El Niño events.
Twelve bird species of restricted range occur in the South Peruvian and north Chilean Pacific slope Endemic Bird Area (EBA B32), which extends from Peru's Lima Department southward to northern Chile. The birds restricted to this coastal strip and the Pacific slope foothills inhabit most of the vegetation associations, with at least three species (Geositta crassirostris, Anairetes reguloides, Sicalis raimondii) known to use the ephemeral lomas vegetation. Three species restricted to this EBA are presently considered threatened, but primarily due to their reliance on riparian vegetation rather than the lomas.
The lomas formations are not generally considered of great economic potential because of the unpredictable and strongly fluctuating environmental conditions within the coastal desert. Nevertheless, investigations of the water potential from wind-blown fog have shown that considerable moisture is available (Oka 1986). However, continuing agriculture or silviculture in a lomas formation would be extremely damaging. Rather, their value lies in the potential for germplasm sources, ecotourism and continued scientific investigations.
The lomas formations are periodically used for grazing livestock, always to the detriment of the natural vegetational communities. Local inhabitants utilize many of the lomas formations for forage in favourable years, and they often gather the woody species for fuelwood (Ferreyra 1977). Destruction of natural communities by overgrazing is quite common (Dillon and Rundel 1991; Dillon 1991). During the exceptional El Niño of 1982-1983, farmers moved large numbers of cattle, sheep and goats from the drought-stricken sierra to various lomas formations in southern Peru. In addition to large-scale destruction of the perennials, these events foster the introduction of more weedy taxa common to higher elevation Andean environments. Both maize and wheat were cultivated in the Lomas de Tacna; the effects of plowing on the soil's seed banks have not been studied (Ohga 1982, 1986).
Urbanization and population growth in coastal cities have placed many lomas localities in peril. In the immediate vicinity of Lima, a number of lomas formations have been severely disturbed or eliminated (e.g. Amancaes, Chorrillos, Cajamarquilla, Cerro Agustino, Manzano), due to the population expansion of the last 60 years (Cuya and Sánchez 1991). Mining has had an impact on both the terrestrial and marine communities (Echegary et al. 1990). Other threats are introduction of orchard species, construction of irrigation canals and mining for the materials used in housing and road construction.
Only a few areas within the desert coast are under the management and protection of the Peruvian government (Díaz-Cartagena 1988). The Reserva Nacional de Lachay (Department Lima, 51 km²), which was established in 1977, is the only lomas with more than 100 species of vascular plants currently protected. The Reserva Nacional de Paracas (1170 km²) and Santuario Nacional de Mejía (7 km²), both primarily aquatic environments, include some adjacent lomas elements. In the Plan Director del Sistema Nacional de Unidades de Conservación (i.e. SINUC), several other coastal sites have been proposed for conservation, including Península Illescas, Department Piura (925 km²); Cerro Campana, Department La Libertad (42 km², 185 spp.); Albuferas de Playa Chica y Paraíso, Department Lima (3 km²); San Fernando, Department Ica (145 km²); and Lomas de Atiquipa y Taimara, Department Arequipa (47 km², 120 spp.) (CDC 1991).
A specimen-oriented computerized database of over 7000 records (LOMAFLOR, Dillon unpublished) has been constructed and the analysis is underway to determine patterns of diversity and endemism within the lomas formations. These data will provide recognition of the areas with maximum biodiversity to establish conservation priorities. The total area of immediately threatened habitat cannot be excessively large (since it will be less than 2000 km²). Prospects for successful conservation efforts in the lomas formations are excellent if the recommended biodiversity priorities are followed (Keel 1987; CDC 1991).
Map 77. Lomas Formations, Peru (CPD Site SA42) and Lomas Formations of the Atacama Desert, Northern Chile (CPD Site SA43)
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This Data Sheet was written by Dr Michael O. Dillon (Field Museum of Natural History,
Center for Evolutionary and Environmental Biology, Department of Botany, Chicago, IL
60605- 2496, U.S.A.).
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