Impact of logging on a mangrove swamp in South Mexico: cost/benefit analysis.
Key words: Cost/benefit, evaluation, habitat, halophytes, logging, mangrove, succession.
Small areas of swamp are being felled at a constant rate in many areas along the coasts of Mexico. These losses ate as harmful as those caused by the oil industry, roads construction, and aquaculture (Serrano et al. 1995, Botero and Mancera-Pineda 1996). Mangrove logging along the state of Guerrero coast has increased because of primitive agriculture and cattle ranching caused by ah economic crisis (Tovilla and Gonzalez 1994). However, there are no records on mangrove destruction or cost/benefit (including long-term environmental changes). Countries such as Costa Rica, Cuba, and Puerto Rico have quantified this phenomenon during the last decade and established land management plans and regulations for mangrove, with notable advances in the conservation of this important ecosystem (Jimenez and Soto 1985, Jimenez 1994).
Litterfall and structure of mangrove forests in Barra de Tecoanapa, Guerrero, Mexico were studied from June 1990 to November 1991 by Tovilla (1998). The present study is part of that study, here we quantified the amount of organic matter provided by the forest to the estuarine system, as well as the amount of wood and fire-wood extracted during that period. At the mouth of the Quetzala river, 3.5 ha of mangroves were felled and burned by the resident community in February of 1992, i.e., after the aforementioned study, which allowed us to study the environmental changes caused by the elimination of the original vegetation cover, as well as the succession of plants that sprouted in the time the land was used for maize crops, and after being abandoned. This study was aimed at estimating the cost/benefit ratio obtained from two crop cycles and the loss of forestry, fishery, and wild fauna resources along the last six years.
MATERIALS AND METHODS
The present study was performed in the wetlands of Barra de Tecoanapa, at the mouth of the Quetzala River (16[grados] 30' 07" N, 98[grados] 45' 11" W) in the state of Guerrero, on the Pacific coast of Mexico. It includes approximately 2 105 ha, of which 915 are covered with mangroves. The climate is type Aw3"(f) warm, semi-dry, with two well marked seasons in the year: the rainy season from June to September, with maximum rainfall in June and September (<1 000 mm/year), and the dry season from October to May, with ah average temperature of 28 to 30[grados]C. The study area was described in detail by Tovilla and de la Lanza (1999).
Three sets of aerial photographs of the Barra de Tecoanapa area were used (1:75 000, 1:50 000, 1:20 000 Anonymous 1997) and interpreted to reconstruct the history of human activity at the site. Production of litterfall and extraction of wood and tire wood was quantified during a period of 18 months (June 1990 to November 1991) following the criteria established by Cintron and Schaeffer-Novelli (1981, 1984) and Birkenhager (1988). Interstitial salinity, atmosphere and soil temperatures at the site and in the remaining adjacent forest, changes in sand, silt, clay, and organic matter proportion, soil compactness and color were measured monthly, from April 1992 to February 1994, following the criteria established by Cintron and Schaeffer-Novelli (1981). Economic losses from reductions in fisheries were estimated following the criteria of Bardecki (1988). Data on the capture of wild fauna were provided by Tovilla (1998). For the cost/benefit analysis, the value of the products extracted from the deforested area was calculated according to supply and demand in local markets, direct use, and intrinsic value according to the criteria determined by Azqueta (1994a; b). Interviews with the farmers of the felled and planted area provided cost/benefit ratios during the planting cycles. Succession of plants that sprouted in the site was collected and identified in 1993 and 1994.
History, structural characteristics and exploitation of the altered site: The aerial photographs indicate that, in 1975, the area was covered by a very compact 20-22 m high mangrove forest. Later, in 1979, the original trees had been eliminated by human activity. As a result, secondary succession of terrestrial plants including Laguncularia racemosa, Avicennia germinans, Prosopis juliflora, Hibiscus tiliaceus, and Cocus nucifera were observed at the periphery and interior regions of the study site. Six years later, in 1985, the area had recovered completely and appeared to be covered by a reasonably dense mangrove forest and terrestrial vegetation. In June of 1990, when this study was started, the site was covered by a dense forest. This forest recovered in 11 or 12 years, up to the point of having 18-20 m high and 32 cm thick trees. The site bordered by the Quetzala river and a 2.5 m wide and 0.9 m deep tidal canal on the right side. This canal flooded up to 40% of a riverine/basin type forest during the rainy seasons and at high tides. The land was covered by a plant community, 21.5 % belonged to Rhizophora mangle-L. racemosa association, distributed from the edge of the canal to the limit of the permanently flooded area. L. racemosa-A, germinans association covered 52% of the area and occupied the seasonally flooded areas. The rest of the area was covered by A. germinans and other terrestrial vegetation. The soil was originally 32.9% silt, 24.5% clay, and 42.6% sand. The forest was young, about to reach maturity and composed of L. racemosa (1071 trees/ha), R. mangle (581 trees/ha), A. germinans (65 trees/ha) and terrestrial vegetation (39 trees/ha). Exploitation took place in 1.7 ha from January to May 1991 and wood extraction affected 13.6 % of the standing trees. The species used for wood and fire wood were L. racemosa (16.8%) and R. mangle (7.9%). A. germinans was not exploited.
The community of Barra de Tecoanapa used the mangrove wood primarily to make poles (2.5-3.5 cm diameter) for domestic use and enciosures for animals. Other uses include the "cuilotes" and "morrillos", which are pieces of wood (4-7.5 and 6-8 cm) used to reinforce fences and build small bridges and piers, as well as the "soleras" and beams or "vigas" (8-10 and 10 cm) used in the construction of adobe walls and to support the roofs of the community houses. The thicker trunks were used as posts and forked props (Table 1). The total volume of the standing wood within the site was 164.03 [m.sup.3], with 41.51 [m.sup.3] of R. mangle, 91.32 [m.sup.3] of L. racemosa, 27.6 [m.sup.3] of A. germinans, and only 3.6 [m.sup.3] of terrestrial vegetation. Considering the volume of the standing wood, the availability of fire wood was 44.01 [m.sup.3]. However, during the present study, the inhabitants extracted only 1.4 [m.sup.3]/year of fire wood.
Litterfall production: Daily and monthly dry weight production of litterfall were 3.9 and 117.2 g/[m.sup.2], respectively, i.e., 14.2 ton/ha/year of litter deposit on the forest floor. Transformation of this production into units of organic carbon, using Brow and Lugo's (1981) conversion factor of 2 g dry weight organic matter/l.8 = 1.1 g C, resulted in a value of 7.8 ton C/year in the felled 3.5 ha. This amount of organic matter was therefore lost to the system when the area was felled. Part of the organic matter produced is exported to the sea where it contributes to the trophic chain. Odum (1970) stated that 10 to 15 % of the organic matter exported by mangrove forests to the sea is transformed into fish, crustacea, molluscs, polychaetes, and isopod tissue, and of this fraction, no less than 20 % is caught in commercial fisheries. If this were the case, 1.9 tons of live tissue of a variety of organisms would have been obtained from the lost carbon and from that, 380 kg of fish, crustaceans, and molluscs were not caught at sea the following year. If an average value of USD1.26/kg were to be assigned, the fishery would have been reduced by 480 USD (Table 6).
Recorded environmental changes: An accelerated salinisation process occurred in December 1992, together with an increase in temperature. In 1994, the river invaded 30 m of the uncovered margin, eroding a surface of approximately 1800 [m.sup.2]. In 1996 and 1997, an additional 0.8 ha area was eliminated when hurricanes Olaf, Nora, Paulina, and Ricki struck the area. Environmental changes observed in the soil of the mangrove forest adjacent to the felled area were minimal, with a temperature gradient of only 5[grados](2 (17-22[grados]C). The maximum temperature of 22[grados]C was recorded in April and May 1993, and the minimum of 17[grados]C occurred during August and September 1993. The air temperature within the forest varied between 22 to 26[grados]C, with extreme temperatures from April to July 1993. In contrast, the minimum temperature in the soil of the felled area was 29[grados]C during September and October 1992 and the maximum was 36[grados]C in April 1994. The minimum atmospheric temperature of 31[grados]C was recorded in October 1992 and the maximum of 39[grados]C during May 1993. The lack of plant cover caused a temperature increase of up to 13[grados]C in the soil and of [grados]C in the air. These variations induced changes in soil color, permeability, and compactness. The color changed from black or dark brown to a reddish grey. Permeability increased via lixiviation and decomposition of organic matter, with a resulting increase in the amount of sand (42.6 to 63.4%). Strong changes in atmospheric and soil humidity (94% in July 1992 to 53% in March of 1993) and less than 10 cm of water in the soil during the rainy season were also recorded. Interstitial salinity in the soil of the adjacent forest varied from 0 psu (practical salinity units) in August and September 1993 to 22 psu during April-May 1993-94). In contrast, salinity was low (12 psu) in September 1992 and high (52) in April 1994 in the felled area. Average salinity varied from 11.8 psu in the forest to 29.6 psu in the area without any vegetation. Additionally, 3 000 [m.sup.2] of soil were lost from upsetting the fragile estuarine balance at the mouth of the Quetzala river.
Cost-benefit of the change in the use of the soil: A total of 3.5 ha were planted with maize from June to November 1992, of which an average yield of 540 kg/ha was obtained at a value of 0.45 cents USD/kg of maize. In total the farmers made 89 USD besides the expenses on labor, planting, and weed and pest control. The site was again planted in 1993; however the yield was reduced to 190 kg/ha of maize, at a value of 0.60 cents/kg and an income of 42 USD (Table 2). The site was abandoned in 1994. Economically, felling of 3.5 ha of mangrove forest produced a loss to the community of an annual contribution of wood for construction and firewood, with an estimated cost of 80 USD/ha for a total of $1 295.4 and 1.7 ha (136 USD) (Table 3).
The lost forest destroyed the natural beauty of the river mouth, which used to be a holiday site and meeting point for the inhabitants of the community and for a large numbers of visitors during the Holy Week and over New Year, providing ah important income for the local economy. Other losses include a refuge, nesting and feeding place of a great number of aquatic and beach birds such as herons, ducks, pelicans, cormorants, frigate-birds and fishing eagles that inhabited the estuary. Part of the beauty and attraction of the area was precisely the great number of birds that congregated to rest in the shallows of the estuary. In addition to the lost birds, other communities were eliminated, such as the crabs Cardisoma crassum, C. quadrata, Gecarcinus quadrata, Goniopsis pulchra and Aratus pisonii, and the molluscs Polymesoda inflata, Tangelus longisimuatus, and Theodoxus luteofasciatus.
Between 1993-94, a 32.5% reduction in estuarine fisheries occurred, primarily because of the destruction of the refuge, reproduction sites, and fishery areas of species such as Centropomus robalito and C. nigrescens ("robalos"), snappers Lutjanus argentiventris, the cat fish Galeichthys caerulescens, and the crabs Callinectes toxotes and C. sapidus along 200 m of the felled river margin, these species represent 79% of the fisheries at the river mouth. Tovilla (1998) collected data on the fisheries in the estuary and within the forest, and on the cost of marketing the fresh product (Table 4). The loss of the mangrove forest also caused silting of the deepest part of the river (2.5-4 m) used as a refuge by these organisms.
This was particularly critical in 1993. The fishery yield of 1991-1993 was averaged, and the average for each species was multiplied by the price of the kilogram of fresh product in the market and compared to the 1994 yield. Losses for the community, recorded as volume and income for the years 1993 and 1994 are presented in Table 4. Although other factors might have affected the decrease in catches, the fact is that the records showed a decrease from 5 305 kg to 4 244 kg of fresh product for 199394, which averaged 1 758 USD and 2 030 USD. Catches recovered in 14.7% and 17.3% in 1995 and 1996, except for "robalos", but never reached the yield of 1991-92.
Wild animals from the mangrove forests ate hunted for self-consumption. The wild fauna is an important protein source for the inhabitants and, contrary to general opinion, the number of animals caught in this wetland is high, as shown by Tovilla (1998), who recorded the capture and sale price of eight species of animals during the 1991-1995 period (Table 5). The number of animals decreased as a result of the habitat's destruction and its fragmentation through felling, as has happened on the opposite side of the river, where hunting has decreased by 18%. Data obtained on the capture of wild fauna indicate that 82% of catches takes place on the right side of the river, in 401 ha of mangrove forest. The average number of animals captured within the mangrove forest results in a catch of 1.03 animals/ha. However, losses may be even greater, according to the degree of complexity, structure and maturity of the altered forest and the type of animal. Considering these numbers, up to three times more herbivorous and omnivorous animals such as iguanas, opossums, and skunks, five times more armadillos, racoons, and badgers, and up to eight times more specific carnivores such as alligators and otters will disappear per felled hectare of forest. The animal losses would average 5.3 animals/ha felled, i.e., 19 animals of those counted must have run away or died when the area was felled. In monetary terms, 56 USD would have been lost in 1993 and 123 USD in 1995 (Table 5).
In the original forest, seven wild bee hives had been recorded in A. germinans (4) and L. racemosa (3) trees, with a production potential of 4-7 liters of honey/beehive/season, equivalent to 77 l/year of honey, which, marketed at a cost of USD 2.10/l, would have provided 162 USD to the community.
An estimation of the total cost caused by logging with respect to the benefits obtained by the farmers indicates a ratio of 32: 1, which is excessively high for the community and is magnified when calculated for the last five years (246: 1) (21 741.03:88.05 USD) taking into consideration the recorded accumulated average inflation of 55% (INEGI 1997) (Table 6). However, the most deplorable costs ate the environmental ones.
Plant succession: The mangrove forest did not recover when the site was abandoned, and in its place a great number of primary and secondary plant species sprouted. A total of 30 species of herbaceous and bushy plants of 16 families were recorded (Table 7). Cyperaceae, Poaceae, Convolvulaceae, Mimosaceae and Sterculiaceae were the best represented families. Of the recorded species, Sesuvium portulacastrum and Batis maritima were classified as strict halophytes (H) due to their ability to withstand high concentrations of salt in the soil (>40 psu), 12 were facultative halophytes (FH) and the rest were terrestrial glycophytes (G). Four species, Cyperus ligularis, C. ciliatus, Prosopis juliflora, and Guazuma ulmifolia, were the most abundant within the site and were present throughout the year; 18 species were classified as common inhabitants, occurring mainly during the rains, and eight species showed up rarely during the year (Table 7).
The recovery capacity shown by the experimental site after the first felling episode (1979) was surprising, but was not repeated after the second episode during the 1994-1998 period. Due to this latter alteration and the effects of the tropical storms and hurricanes that struck the area, the river mouth became more erratic and an accelerated process of erosion set in, as documented by Tovilla (1998). Similar changes in temperature and salinity have been observed in other localities where mangrove cover has been eliminated (Soto 1988). These changes may have been so drastic that they inhibited recovery of the mangrove forest and in its place a low diversity plant community without any economic value was established, including species resistant to hypersalinity conditions. A recovery of only 30 % was recorded in 1998 after five years.
Inhabitants use the wood only for construction and fuel, occasionally extracting wood to send outside the community for the construction of beach huts, as Tovilla (1998) found in a detailed study of the extraction of wood and firewood throughout the swamp. Records from other Latin American countries such as Venezuela, Costa Rica, and Cuba show similar uses (Luna-Lugo 1976, Chong 1988, Menendez and Priego 1994). Litterfall production recorded in this study is matched only by that produced in mangrove swamps on the Equator, in Colombia, Ecuador, New Guinea, and Malaysia (Hernandez and Mullen 1975, Sasekumar and Loi 1983). The importance of the mangrove forests in Barra de Tecoanapa is evidenced by their very high production rates despite their location in ah area of low rainfall (<1 000 mm/year), as shown by Tovilla and Gonzalez (1994) and Tovilla (1998). Several studies have shown that commercially important fishes, such as snappers, perch, robalo, red snapper, and mojarra depend on the detritus provided by mangrove forests (Cardoso 1980, Ley et al. 1994, Pinto and Punchihewa 1996). Turner (1977) recorded a significant correlation between the amount of shrimp collected at sea and the extension of adjacent mangrove forests.
In Mexico, no attention has been paid to the exploitation of wild animals and honey in mangrove swamps. These resources, although considered as subsistence or low quality products, could be of great benefit to the economy of local residents. For example, in Cuba and Costa Rica, large quantities of honey are extracted annually. Cuba is an exceptional case, as every year between May and July up to 45 000 beehives are placed under mangrove trees (Bradbear 1990, Anonymous 1994).
The present analysis exemplifies the events occurring along the coasts of Mexico, without any environmental regulation from federal, state, and municipal authorities. Environmental destruction results from diverse factors, the most important are poverty and excessive growth of human population along the coasts, lack of adequate regulations to control the use of these resources, and lack of counseling and education in regard to the viability of changes in land use. Population growth must be reduced in the following years to minimize these costs. The lack of adequate methods to assess mangroves in economic terms has caused people to consider them wastelands with no value and as risky unhealthy areas that should be adapted for an alternative and more lucrative use. According to Odum and Campbell (1994), there ate at present at least four methods to estimate the contributions made by mangroves to economic activities. However, their application in Latin America is still limited and sometimes excessively complicated (Aguero 1994). These methods have been developed as a response to the needs of developed countries in which the cultural and socio-economic conditions are very different from ours.
TABLE 1 Volume of standing wood and extraction of wood and firewood during 1990-1991 CUADRO 1 Biomasa, extraccion de madera y lenos durante 1990-1991 Age R. mangle Felled trees L. racemosa Felled trees class standing/t (1) /w extracted standing/t (1) /w extracted (cm) wood wood ([k.sup.2]) ([k.sup.2]) 2.5-5 141 287 72/347.9 5.1-10 158 19/262.2 278 56/459.2 10.1-15 139 16/537.6 183 30/588 15.1-20 61 11/403.7 121 15/501 20.1-25 39 97 5/213 25.1-30 22 54 30.1-35 12 37 35.1-40 9 14 Total 581 46/1203.5 1071 180/2310.4 % E (5) 8.50 17.10 Age Volume Volume Volume class standing standing firewood (4) (cm) wood (3) wood (3) 2.5-5 5.1-10 1.58 2.78 1.45 10.1-15 5.56 7.32 4.29 15.1-20 6.10 12.10 6.06 20.1-25 7.80 19.4 9.06 25.1-30 7.48 19.98 9.15 30.1-35 6.24 19.24 8.49 35.1-40 6.75 10.5 5.75 Total 41.51 91.32 44.01 % E (5) Number of standing trees per age class. (2.) Number of felled trees and weight (k) of extracted wood after 25 to 30 days in the Sun. (3.) Volume of standing wood of R. mangle and L. racemosa. (4.) Volume of firewood estimated for both species. (5.) Exploitation of each species. TABLE 2 Cost-benefit of the logging of a mangrove area and its change into a field for crops CUADRO 2 Costo-beneficio de la deforestacion del area manglar y su cambio a un campo para cultivo First crop cycle 1992 Activity Cost (USD) Logging of the site 7.9 Burning/planting/cleaning 8.9 Plague control 3.0 Harvest 2.0 Total investment 21.9 Harvest earnings 89.5 Net benefits 67.6 Second crop cycle 1993 Activity Cost (USD) Cleaning of the site 4.2 Planting 2.0 Cleaning and plague control 12.0 Harvest 3.2 Total investment 21.6 Harvest earnings 42.0 Net benefits 20.40 Average monthly income of a fisherman in 1992 16.8 USD Average monthly income of a fisherman in 1993 20 USD TABLE 3 Cost of the wood and firewood exploited during the year 1990-1991 CUADRO 3 Costo de la madera y lenos explotados en los anos 1990-1991 Total cost Description Size of pieces(m) Unit cost(USD) (USD) Mangrove pole 2.0-2.5 <0.5 /piece 3.8 Cuilote 2.0-3.0 0.20 4.0 Morillo 2.5-3.0 0.30 17.7 Solera 2.5-3.5 0.40 12.6 Beam 3.5-4.5 0.50 8.4 Post 2.0-2.5 0.50 13.7 Forked prop 2.5-3.5 0.60 3.2 Firewood (64) 20-25 kg weight 0.25 16.8 Total cost 80 USD TABLE 4 Volumes and costs of marketing of some fish and crustaceans collected at the river mouth during the period 1991-1994 CUADRO 4 Volumenes y costos de comercializacion para algunos peces y crustaceos en la boca del rio durante el periodo 1991-1994 Catches (k) (1) 1991 1992 1993 Robalo 872: 0.6 1329: 0.7 903: 0.9 Snappers 316: 0.6 192: 0.7 171: 0.9 Cat fish "cuatete" 11323: <0.5 9455: 0.2 5476: 0.3 Swimming crab 2091: 0.3 (2) 3199: 0.3 2534: 0.4 Volume/cost 14602: 2 972 14175: 3897.0 9084: 3113.0 Estimated decrease 14602: 2 972 14175: 3897.0 14389: 4872.0 Net loss 5305: 1758 USD Catches (k) (1) 1994 Robalo 1295: 1.1 Snappers 145: 1.1 Cat fish "cuatete" 6908: 0.3 Swimming crab 1991: 0.5 Volume/cost 10339: 3912.0 Estimated decrease 14583: 6153.0 Net loss 4244: 2030 USD (1) Fresh weight and cost in kilograms. (2) Price per 12 animals. TABLE 5 Capture of wild animals and marketing costs during the period between 1991-1995 CUADRO 5 Captura de animales silvestres y costo de comercializacion durante el periodo entre 1991-1995 Animals 1991 1992 1993 1994 Iguanas 87: 0.5 (1) 132: 0.84 144. 1.0 111: 1.5 Armadillos 132: 0.8 157: 1.2 123: 1.5 108: 2.0 Opossumus 69: 0.4 79: 0.5 109: 0.6 105: 0.9 Racoons 52: 0.6 64: 0.7 74: 0.8 82: 1.0 Skunks 9: 0.3 28: 0.4 20: 0.5 29: 0.6 Badgers 5: 0.6 15: 0.7 17: 0.9 22: 1.0 Otters 11:? 6: 0.5 7: 0.8 2: 1.0 Alligators 14: 1.1 13: 1.2 11: 1.5 3: 2.0 Total 369: 240 USD 494: 441 USD 506: 531 USD 472: 648 USD Animals 1995 (2) Iguanas 86: 2.0 Armadillos 19: 3.1 Opossumus 41: 1.1 Racoons 53: 2.0 Skunks 14: 1.0 Badgers 12: 1.2 Otters Alligators Total 225: 430 USD (1) Number of animals captured and cost per unit. (2) Data up to June of 1995. TABLE 6 Cost-benefit ratio expressed in USD CUADRO 6 Coeficiente costo-beneficio expresado en dolares estadounidenses Benefits Income Products and services Costs (USD) (kg of maize) USD Extraction of wood and firewood 136.0 1992 cycle ... 1850 67.6 Estaurine fisheries 1895.0 1993 cycle ... 665 20.4 Marine fishery component 480.0 Wild fauna 133.0 Honey 162.0 Total 285.0 USD Cost after 5 years+55% (1) 21 741USD Harvet 21515 kg 88.0 USD (1) Costs for the five years during which the site recovered by only 30%, plus the average inflation recorded during the same period. TABLE 7 List of plant species that colonised the site after being abandoned CUADRO 7 Lista de especies de plantas que colonizan el sitio despues de que ha sido abandonado S (SPU) Occur- Family Species T (1) rence (2) Aizoaceae Sesuvium portulacastrum L. H C Anacardiaceae Anacardium occidentale L. G C Arecaceae Astrocarium mexicanum Liebm. G C Batidaceae Batis maritima L. H C Chrysobalanaceae Chrysobalanus icaco Kunth G C Convolvulaceae Ipomea pes-caprae (L.) Sweet FH C I. stolonifera (Cirillo) Gmelin FH C Merremia umbellata (L.) Hallier f. G C Cucurbitaceae Momordica charantia L. G C Cucumis anguria L. G R Cyperaceae Oxycaryum cubense (Poeppig & Kunth) FH C Cyperus ligularis L. FH A C. ciliatus Junghuhn FH A Carex cortesli Liebm FH C Malvaceae Hibiscus tiliaceus L. G C Kosteletrkya pentasperma (Bert.) Griseb FH R Mimosaceae Acacia hindsii Berth Schildl & Cham. FH C A. sphaerocephala FH R Prosopis juliflora (SW.) DC. FH A Nyctaginaceae Salpianthus arenarius Kunth FH R Papilionaceae Crotalaria cajanifolia HBK. G C Poaceae Boutelowa repens (Kunth) Scribner & Merr FH R Dactyloctenium aegyptium (L.) Willd G C Digitaria sanguinalis (L.) Scop. G C Phragmites australis (Cav.) Trim. ex Steudel G C Scrophulariaceae Scoparia dulcis L. G R Sterculiaceae Walthenia americana L. G C W. preslii Walp G C Guazuma ulmifolia Lam G A Turneraceae Turnera ulmifolia (L.) G R (1) Tolerance to salinity in the soil: strict halophytes (H), facultative halophytes (FH), glycophytes (G). (2) Frequency of occurrence throughout the year: A-abundant, C-common, R-rare.
We thank Eladio Gonzalez Angelito, Enoch Gonzalez Angelito, Hipolito Bibiano, Salvador Hernandez Pulido, and Minerva Perez for field assistance.
En el presente trabajo se estudian los cambios causados por la deforestacion de un manglar al sureste de Mexico. La vegetacion original incluia a R. mangle, L. racemosa y A. germinans. Se registro una sucesion aparetiendo halofitas estrictas, facultativas asi como glicofitas. En la epoca seca la temperatura aumento 13[grados]C en el suelo y 11[grados]C en el aire, y la salinidad alcanzo hasta 52 ups; ademas, se modifico la fauna y los ciclos biogcoquimicos; cambiaron las condiciones esteticas, se presento una fuerte erosion y por lo tanto una perdida economica. El area se ha recuperado en un 30% despues de cinco anos.
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Cristian Tovilla-Hernandez (1), Guadalupe Espino de la Lanza (2) and D. Edith Orihuela-Belmonte (3)
(1) El Colegio de la Frontera Sur (ECOSUR), Unidad Tapachula, Fax 525 962 811 15 E-mail firstname.lastname@example.org.
(2) Instituto de Biologia, UNAM e-mail email@example.com.
(3) Facultad de Biologia Marina, Universidad Autonoma de Sinaloa.
Received 11-VIII-2000. Corrected 31-VIII-2000. Accepted 9-X-2000.
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|Author:||Tovilla-Hernandez, Cristian; Espino de la Lanza, Guadalupe; Orihuela-Belmonte, D. Edith|
|Publication:||Revista de Biologia Tropical|
|Date:||Jun 1, 2001|
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