Los modelos de conservación biológica divergente y convergente: una mirada desde las perspectivas de la ecología del paisaje y la teoría de metapoblaciones / Land-sparing and land-sharing: a lot from the perspectives of landscape ecology and metapopulation theory

La pérdida de biodiversidad en paisajes agrícolas es un asunto preocupante a nivel mundial y tema central de mucha de la investigación contemporánea. Este fenómeno puede ser abordado desde dos perspectivas principales: la de la biología de la conservación y la agroecología. La primera enfatiza la importancia de la preservación de los ecosistemas naturales, ya que otros usos del suelo son considerados de legitimidad menor. Para la segunda, el interés se dirige a los agroecosistemas y la biodiversidad es relevante solamente si tiene una conexión con la sostenibilidad de los mismos. La realidad, es que hay agroecosistemas que albergan riqueza en el mismo orden de magnitud que en áreas conservadas y que la pérdida de algunas especies, aparentemente sin valor en la producción del sistema, puede desencadenar efectos cascada si estas son clave en las redes tróficas. Los modelos conceptuales de conservación biológica divergente/convergente, brindan argumentos sobre lo que debería ser la relación entre la agricultura y la biodiversidad; sin embargo, debido a su carga ideológica usualmente derivan en problemas de contextualización. Aquí se refuerzan elementos que parten de la ecología del paisaje y la teoría de metapoblaciones, cuyo soporte proviene de datos empíricos, para repensar este debate con implicaciones para las estrategias de conservación en la región.

Biodiversity loss in agricultural landscapes is a global issue of concern, and it is subject of much contemporary research. This phenomenon can be addressed through two main perspectives: conservation biology and agroecology. The first emphasizes the importance of preserving natural ecosystems, considering the study of other land uses to be less important. The second focus is geared towards agro-ecosystems, and biodiversity is considered to be relevant only if it has a connection with sustainability. The reality is that there are agro-ecosystems that can harbor species in the same order of magnitude as in conserved areas, and that the loss of species that have no apparent role in the system’s productivity can provoke cascade effects if they are critical in the trophic web. The divergent/convergent conceptual models of biological conservation provide arguments of what should be the relationship between agriculture and biodiversity; however, their ideological backgrounds usually derive in contextualization problems. Here we reinforce basic elements of landscape ecology and the metapopulation theory both with support in empirical data, as a way of rethink this debate with implications in regional conservation strategies.

Evaluation of local energy sources in milk production in a tropical silvopastoral system with Erythrina poeppigiana.

An experiment was carried out to determine the effect of four local energy sources (sorghum grain, green banana, polished rice, and sugarcane molasses) fed to dairy cows on intake, milk production and composition, and economic viability in a silvopastoral system in Costa Rica (Turrialba). Twelve grazing cows (Jersey × Central American Milking Creole), with a mean live weight of 332 kg (SD 34), were supplemented with 0.5 kg of dry matter (DM)/100 kg/LW of Erythrina porppigiana fresh foliage daily. Experimental design was a replicated change-over 4 × 4 Latin Square. The pasture composition was 11 and 17 % of star grass (Cynodon niemfuensis), 32 and 28 % of ruzzi grass (Brachiaria rusisiensis), and 45 and 42 % of natural grasses (Axonopus compresus and Paspalum conjugatum) at initial and final times of the essay, respectively. The grass allowance was 30.14 DM/cow/day. Significant differences were found among treatments for variable milk fat content (P < 0.05). Sorghum presented the highest (41.2 g/kg milk) content of milk fat, followed by green banana (39.2 g/kg milk), polished rice (38.3 g/kg milk) and molasses (38.1 g/kg milk). Non-significant differences (P > 0.05) resulted for total milk production (sorghum 9.0 kg/cow/day; green banana 8.9 kg/cow/day; polished rice 8.8 kg/cow/day; molasses 8.6 kg/cow/day) and fat-corrected milk (FCM). The financial analysis showed that all treatments were economically viable; however, supplementation with green bananas and molasses were the most favorable due to the low costs incurred.

Food sovereignty: an alternative paradigm for poverty reduction and biodiversity conservation in Latin America.

Strong feedback between global biodiversity loss and persistent, extreme rural poverty are major challenges in the face of concurrent food, energy, and environmental crises. This paper examines the role of industrial agricultural intensification and market integration as exogenous socio-ecological drivers of biodiversity loss and poverty traps in Latin America. We then analyze the potential of a food sovereignty framework, based on protecting the viability of a diverse agroecological matrix while supporting rural livelihoods and global food production. We review several successful examples of this approach, including ecological land reform in Brazil, agroforestry, milpa, and the uses of wild varieties in smallholder systems in Mexico and Central America. We highlight emergent research directions that will be necessary to assess the potential of the food sovereignty model to promote both biodiversity conservation and poverty reduction.

Resolving the conflict between ecosystem protection and land use in protected areas of the Sierra Madre de Chiapas, Mexico.

Livelihoods of people living in many protected areas (PAs) around the world are in conflict with biodiversity conservation. In Mexico, the decrees of creation of biosphere reserves state that rural communities with the right to use buffer zones must avoid deforestation and their land uses must become sustainable, a task which is not easily accomplished. The objectives of this paper are: (a) to analyze the conflict between people's livelihoods and ecosystem protection in the PAs of the Sierra Madre de Chiapas (SMC), paying special attention to the rates and causes of deforestation and (b) to review policy options to ensure forest and ecosystem conservation in these PAs, including the existing payments for environmental services system and improvements thereof as well as options for sustainable land management. We found that the three largest PAs in the SMC are still largely forested, and deforestation rates have decreased since 2000. Cases of forest conversion are located in specific zones and are related to agrarian and political conflicts as well as growing economic inequality and population numbers. These problems could cause an increase in forest loss in the near future. Payments for environmental services and access to carbon markets are identified as options to ensure forest permanence but still face problems. Challenges for the future are to integrate these incentive mechanisms with sustainable land management and a stronger involvement of land holders in conservation.

Biodiversity loss in Latin American coffee landscapes: review of the evidence on ants, birds, and trees.

Studies have documented biodiversity losses due to intensification of coffee management (reduction in canopy richness and complexity). Nevertheless, questions remain regarding relative sensitivity of different taxa, habitat specialists, and functional groups, and whether implications for biodiversity conservation vary across regions.We quantitatively reviewed data from ant, bird, and tree biodiversity studies in coffee agroecosystems to address the following questions: Does species richness decline with intensification or with individual vegetation characteristics? Are there significant losses of species richness in coffee-management systems compared with forests? Is species loss greater for forest species or for particular functional groups?and Are ants or birds more strongly affected by intensification? Across studies, ant and bird richness declined with management intensification and with changes in vegetation. Species richness of all ants and birds and of forest ant and bird species was lower in most coffee agroecosystems than in forests, but rustic coffee (grown under native forest canopies) had equal or greater ant and bird richness than nearby forests. Sun coffee(grown without canopy trees) sustained the highest species losses, and species loss of forest ant, bird, and tree species increased with management intensity. Losses of ant and bird species were similar, although losses of forest ants were more drastic in rustic coffee. Richness of migratory birds and of birds that forage across vegetation strata was less affected by intensification than richness of resident, canopy, and understory bird species. Rustic farms protected more species than other coffee systems, and loss of species depended greatly on habitat specialization and functional traits. We recommend that forest be protected, rustic coffee be promoted,and intensive coffee farms be restored by augmenting native tree density and richness and allowing growth of epiphytes. We also recommend that future research focus on potential trade-offs between biodiversity conservation and farmer livelihoods stemming from coffee production.

Sistemas agroforestales y almacenamiento de carbono en comunidades indígenas de Chiapas México / Agroforestry systems and carbon stocks in indigenous communities from Chiapas México

Una consecuencia de la agricultura de roza-tumba-quema (r-t-q) es la conversión de áreas boscosas a sistemas agrícolas. Esta práctica contribuye a la deforestación, el deterioro de los suelos, a las emisiones de carbono (C) y, por lo tanto, al efecto invernadero. El objetivo de este estudio fue evaluar los reservorios de C en cultivos de maíz tradicionales y en sistemas agroforestales (taungya, barbechos o acahuales naturales y enriquecidos), y explorar su relación con la edad y su complejidad funcional y estructural. En el marco del proyecto Scolel’te se realizaron inventarios en 25 parcelas circulares en cuatro comunidades indígenas del municipio de Chilón, Chiapas, México, usando métodos destructivos para la estimación de C, a excepción de árboles, juveniles y raíces gruesas, para los cuales se emplearon fórmulas alométricas. Una mayor complejidad de los sistemas derivó en mayor acumulación de carbono. Taungya, milpa, barbecho enriquecido y natural presentaron 109,4; 127,9; 150,1 y 177,6Mg C·ha-¹, respectivamente. La materia orgánica del suelo fue el mayor reservorio (70% del C total en todos los sistemas); la biomasa viva y materia orgánica muerta aportaron un tercio del C total. El C total mostró incremento con la edad del sistema en taungya y barbecho natural, mientras que en la milpa se encontró una relación negativa entre materia muerta y edad. Los sistemas taungya y barbecho enriquecido pueden reducir los ciclos de r-t-q, ofrecer el servicio ambiental de captura de C y producir bienes para la población local.

Relaciones alométricas para la predicción de biomasa forrajera y leña de acacia pennatula y guazuma ulmifolia: en dos comunidades del norte de chiapas, méxico / Allometric relations for forage and fuel wood prediction in acacia pennatula and guazuma ulmifolia: from two localities in northern chiapas, mexico

Acacia pennatula (Schltdl. y Cham) Benth. y Guazuma ulmifolia Lam. son especies importantes como forraje y leña en las áreas tropicales secas y subhumedas. Sin embargo se desconoce la producción con respecto a variables alométricas. Se establecieron modelos alométricos para predecir la acumulación de forraje y leña de estas especies en condiciones naturales de vegetación secundaria en dos localidades del norte de Chiapas, México. En marzo 2001 se realizó una poda de homogenización a 23 árboles de cada especie, cuantificándose la cantidad de leña. La producción de forraje se calculó mediante la cosecha de rebrotes seis meses después de la poda. La producción de materia seca de forraje se estimó mediante varios modelos predictivos utilizando diámetro basal (db), diámetro a la altura de pecho (dap), volumen del tacón, número de rebrotes por árbol (nra), longitud de rebrote y diámetro de la base del rebrote como variables alométricas.

Woody plant diversity and structure of shade-grown-coffee plantations in northern Chiapas, Mexico

Shade-grown coffee is an agricultural system that contains some forest-like characteristics. However, structure and diversity are poorly known in shade coffee systems. In 61 coffee-growers' plots of Chiapas, Mexico, structural variables of shade vegetation and coffee yields were measured, recording species and their use. Coffee stands had five vegetation strata. Seventy seven woody species mostly used as wood were found (mean density 371.4 trees per hectare). Ninety percent were native species (40 of the local flora), the remaining were introduced species, mainly fruit trees/shrubs. Diametric distribution resembles that of a secondary forest. Principal Coordinates Analysis grouped plots in four classes by the presence of Inga, however the majority of plots are diverse. There was no difference in equitability among groups or coffee yields. Coffee yield was 835 g clean coffee per shrub, or ca. 1,668 kg ha-1. There is a significant role of shade-grown coffee as diversity refuge for woody plants and presumably associated fauna as well as an opportunity for shade-coffee growers to participate in the new biodiversity-friendly-coffee market.