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Selected Abstracts
AGROECOLOGY AND SUSTAINABILITY: THE ECOLOGICAL FRAMEWORK
Preserving the productivity of agricultural land over the long term requires sustainable food production. Sustainability is achieved through alternative agricultural practices informed by in-depth knowledge of the ecological processes occurring in farm fields and the larger contexts of which they are a part. From this foundation we can move towards the social and economic changes that promote sustainability of all sectors of the food system. Sustainability means different things to different people, but there is general agreement that it has an ecological basis. Several examples are presented from research designed to measure ecological components of sustainability. The connection between specific ecosystem characteristics and sustainable agroecosystem function is explored. A framework for integrating ecological parameters with social and economic parameters is also proposed.
AGRICULTURAL SUSTAINABILITY UNDER (SEMI-) ARID CONDITIONS: A case study of Iran There is a high diversity of climatic conditions in semi-arid regions of the world. In Iran, areas with a mild summer and cold winter, where the mean annual rainfall varies between 300 and 500 mm and the mean annual temperature is around 16 (C, are considered as semi-arid. The major problem in these areas is water shortage, which leads to overexploitation of groundwater and consequently to aridification. The occurrence of salt-affected soils, high population growth rate and inappropriate changes in land tenure are a few factors aggravating the problem. The assessment of agricultural sustainability in the Hamadan-Komidjan area, representing the semi-arid Iran, started with an integrated analysis of the ongoing agricultural systems. Traditional and advanced systems were modelled and further assessed for sustainability. Three approaches were implemented for this purpose. Application of the energy balance (input/output ratio) yielded 1/7 and 1/2 for the traditional and the advanced systems, respectively. To broaden the concept of sustainability, two other approaches, called here socio-ecologic model and six pillar model, were applied. In both models, several sustainability indicators are employed, which are discussed in the paper.
STRATEGIES FOR INCREASING SUSTAINABILITY IN MEDITERRANEAN CROPPING SYSTEMS WITH SELF-RESEEDING ANNUAL LEGUMES
In search of strategies for increasing sustainability in cropping systems, we have been focusing for ten years on the use of plant resources, such as the self-reseeding winter annual legumes (Trifolium and Medicago species) native to the Mediterranean environment. Although subclover and annual medics are well-known forage crops in cereal-ley farming systems under the Mediterranean climate all over the world, their use is practically unknown in more intensive cash-crop sequences, such as the two -year rotation between a winter cereal( wheat, barley) and a summer crop ( rain-fed sunflower; irrigated corn) which is common in Central Italy. In this rotation, we have conceived the establishment and use of an annual legume as a living mulch in winter cereals and, after its self-reseeding, as either a green manure or a mulch for the succeeding summer crop. This alternative cropping system has proved to have the potential, while maintaining the same cash-crop sequence of the conventional one, to induce a significant shift towards a less energy-intensive and a more environmentally -friendly management type. This paper reports on the main steps and achievements of our research in ten years of activity, starting from the screening of the self-reseeding legumes species and cultivars and ending up with the implementation and performance assessment of the whole alternative cropping system ( winter cereal-summer crop rotation). While several of the tested subterranean clover species and cultivars were able to grow sufficiently as a living mulch in the winter cereal, without severely reducing the cereal grain yield, and to regenerate, annual medics completely failed to re-establish, revealing themselves unsuitable for the alternative cropping system. The tillering capacity of the winter cereal turned out to be a crucial element to grain yield performance. Differences in grain yield between wheat with a living mulch and wheat in pure stand were more severe with increasing availability of water (in wet years) and nitrogen fertilizer, i.e. with factors which favour tillering capacity . Unfortunately, modern wheat varieties are characterized by poor tillering capacity, as they have been selected to grow in high density pure stands. This suggests that modern breeding trends are depriving both intercropping research and practice of their necessary genotype basis. A subclover living mulch proved able to regenerate and to provide the succeeding crop with abundant and nitrogen-rich residues. A positive correlation between the amount of subclover biomass ploughed in and the vegetative and productive characteristics of sunflower was found in both dry and wet years . Subclover green manuring was so effective that sunflower yield in the alternative system was higher than that of the conventional one fertilized with 130 kg/ha of inorganic N. Subclover green manuring also affected biomass and composition of the weed community in the sunflower crop. Subclover mulch from a sod strip intercropping system with wheat was also effective to positively influence the above-ground biomass production of the succeeding corn crop, the effect being dependent on the amount of dry mulch left by the different subclover species and cultivars.
NEMATODE COMMUNITIES: INDICATORS OF SOIL HEALTH
Nematode communities (plant-parasitic and free-living), characterized by life history strategy (maturity) indices, were evaluated as measures of agricultural soil health. Based on variance component, power and reliability analyses, maturity indices perform better than indices of trophic diversity, abundance or proportions of individual taxa. Maturity indices correlate negatively with nitrogen availability and positively with rates of decomposition, thus, reflecting ecosystem function. Forage and pasture crops may serve as reference sites for monitoring soils associated with annual crops. The cumulative frequency distribution of index values for soils with perennial crops (Medicago sativa L., Festuca arundinacea Schreb.) reflected a more complex foodweb and, thus, a less disturbed biological community than soils with annual crops (Glycine max (L.) Merr., Zea mays L., Triticum aestivum L.). In contrast, maturity index values were similar for soils managed by conventional or organic techniques suggesting that cultivation disturbs soil communities more than chemical applications. Management practices often represent a confounded mixture of physical and chemical attributes that can be separated using canonical correspondence analysis. Net impacts of physical and chemical management on individual genera were either cumulative or canceled by opposite responses. Regional-scale studies across North Carolina and Nebraska (USA) suggest that assessments of soil health based on nematode communities can be implemented on a geographic resolution of 125,000-200,000 km2 of land area. Studies of this scale require a minimum sample size of 25 fields with one composite soil sample analyzed per field to detect 10% change (with 0.8 power) between two time periods.
SOIL PHYSICS, FUNGI AND PHOSPHORUS: MEASURING SUSTAINABILITY IN THE AUSTRALIAN WHEATBELT
Soil structural decline is a long term problem for the sustainability of Australian wheat production. Most conventional agricultural responses have been conservation farming techniques using herbicides and reduced tillage. This has created new problems, for example increases in soil fungal diseases. Research on organically farmed soils in the central eastern wheat belt indicates that improvements in soil physical properties may be achieved through other techniques. Improvements include greater soil aggregate stability, water infiltration and recovery from tillage events compared to paired conventionally farmed soils. These improvements occur despite the maintenance of tillage in the organic system to control weeds and prepare seed-beds. The organic soils exhibit greater biological activity particularly that of VAM fungi. Greater densities of fungal hyphae in the organic system correlate highly with a greater percentage of larger water-stable soil aggregates. The differences in VAM activity in the paired soils are due to the absence of soluble phosphatic fertilizer in the organic system and its presence in the conventional system. As the availability of phosphorus is a key limiting factor for wheat production in these systems, increased soil structural properties in the organic system are purchased at the cost of reduced yields. Conversely, in the conventional system, increased productivity is gained at the expense of known soil structural decline. The mediation of soil biological activity by management techniques produces a known trade-off between productivity and sustainability.
A COMPARISON OF NUTRIENT CYCLING IN ORGANIC AND CONVENTIONALLY MANAGED STRAWBERRY FIELDS IN CALIFORNIA, U.S.A. AND IN NANJING, CHINA
The state of nutrient flow and cycling in agroecosystems is an indicator of their sustainability. We compare the cycling of nitrogen in organic and conventionally managed strawberry fields in California, USA and in Nanjing, China, conducted as comparative on-farm experiments for three years at each site. Nutrient budgets and cycling studies have been done at scales that range from the individual crop up to the entire farm agroecosystem. However, very few have used statistical methods that allow reliable comparisons between whole-system indicators of the status of nutrient cycles. We will demonstrate statistically-reliable methods for comparing nitrogen cycles of agroecosystems under different agricultural managements in different regions and examine the potential of the Cycling Index as a quantitative indicator of ecological sustainability in agroecosystems. The Cycling index of other elements, such as phosphorous and potash, will also be discussed.
VILLAGE-SCALE NITROGEN CYCLING AND ECOLOGICAL SUSTAINABILITY IN CHINESE VILLAGE ECOSYSTEMS
Comparing the nitrogen cycles of traditional village ecosystems with those of contemporary high-input systems can help identify indicators for sustainable agroecosystem management. Traditional agriculture in China's Yangtze Delta Region sustained high rice yields and dense human populations for centuries without large anthropic nitrogen imports, water pollution, or diminished productive capacity. Chemical-intensive agriculture and doubled human populations have now transformed these traditional systems from a nitrogen-limited to a nitrogen-saturated state, causing pollution and dependence on chemical nitrogen inputs. Village-scale patterns of nitrogen storage, cycling, and throughflow have been characterized within horizontal and vertical landscape components of Xiejia village, Wujin county, Jiangsu province, under traditional (circa 1930) and contemporary (1994) management. Field data collected on-site (1993-1996) were combined with published data and expert estimates using a Bayesian statistical approach. Results reveal minor changes in landscape structure caused by modern management, combined with major changes in spatial patterns of nitrogen flow caused by the use of chemical fertilizers, changes in perennial cropping patterns and altered management of human waste and canal sediments. Monte Carlo uncertainty analysis facilitated statistically valid comparisons between traditional and modern whole-village nitrogen cycle descriptors. Combining village-scale nitrogen cycle analysis with a Bayesian statistical approach lays the foundation for development of larger-scale indicators of ecologically sustainable agricultural management and human carrying capacity.
AGROECOLOGICAL AND ECONOMIC INDICATORS OF SUSTAINABILITY IN COFFEE FARMING IN VERACRUZ, MEXICO
For Central Veracruz, the second largest coffee producing region in Mexico, governmental deregulation, privatization and economic globalization, pest outbreaks (e.g. coffee borer) in combination with emerging practices of sustainable agriculture raise critical questions about future directions of coffee farming. No agroecological benchmarks or sustainability indicators exist to assess the scope and environmental impact of such technological changes over the medium and long term. A research is being carried out in three counties to build up a methodology for defining and measuring indicators of sustainability in such coffee agroecosystems; their spatial distribution is mapped and correlated in order to detect "hot spots" where both, ecological and economic sustainability, might be increased, degraded or maintained. The methodology is based in a "dynamic access model" where types of farmers exert farming choices that have an impact on the environment which in turn modifies the conditions of reproduction of natural resources as well as farmers'. Indicators being tested here are: 1) agroecological: intercropping biodiversity, nutrient balance, erosion and biological control; 2) economic: asset/debt ratio, farm profitability. farm autonomy, and inequality in resource and wealth distribution. Preliminary results suggest that a combination of land availability, type of farming and intercropping biodiversity manages to promote non sustainable practices like chemical weeding and overfertilization. Organic practices like composting and entomopathogen fungi spraying show adoption barriers that distort them creating the illusion of "organic" or "sustainable" agriculture. REGIONAL INDICATORS OF SUSTAINABILITY IN "LA SIERRA DE SANTA MARTA", VERACRUZ, MEXICO This paper explores at a regional scale what is being sustained, who is to be benefited from, in what way, and how the benefits are being distributed not only in the social but in environmental aspects as well. The study region involves almost 50 000 inhabitants settled in a 350 000 h area where cloud, rain and temperate forest are part of a biosphere reserve. Concerns about social and economic development program impacts on the environment have led to a sustainable development search and ways to measure and monitor it. In response to this, a set of indicators compiling disaggregated information from different disciplines was developed. Indicators like profits, productivity, real wages and family work, crop adaptability, agroecological and social resilience, average production, sociopolitical structure, biodiversity and soil impact, and, health and social marginalization were measured. Inequity and productivity indexes were evaluated in "Sierra de Santa Marta", a tropical region in Southern Golfo de Mexico where livelihood is based on different strategies like policulture, forest exploitation, cash monocrops and livestock. Indicators show that there is a subsistence economy where low income peasants live on lesser marginality conditions due to environmental subsidy which provides water, shelter, market products (wild animals and plants)and high agroecological resilience to disturbance conditions. This self-sufficiency development model is pervaded by a intensive production model where environmental services are exported out of the region leading to a high marginality sector that need cash-market as a way to supply all its needs.
ENVIRONMENTAL SOCIOLOGY AND AGROECOLOGY: IN SEARCH OF TRANSDISCIPLINARY CONCEPTS AND THEORIES FOR THE NEW MILLENNIUM
Standing at the threshold of a new millennium is an unusual situation in which to find oneself; an experience that prompts both reflection and projection. Environmental change is one of humanity's somewhat less novel preoccupations, although currently observed and debated, mainly negative trends of environmental change have added more urgency to our discussions about the veracity and consequences of such observations. Environmental sociology, like agroecology, can be viewed as an intellectual response to the dilemma created by such observations and, in particular, the construction and pursuit of `sustainable development'. Both of these intellectual developments recognise, either implicitly or explicitly, the strong links that exist between changes in nature and changes in society. The view from environmental sociology suggests that many changes in the structural and behavioural characteristics of human societies reflect changes in nature and the way in which societies (re-)construct, (re-)fashion or (re-)invent their environments, both physically and cognitively. At the same time, social adjustment to novel environmental `realities', whether physically tangible or simply appealing to collective social conscience, exerts further successional/evolutionary pressure on nature, leading to new environmental conditions, both `real' and `perceived'. In short, both society and nature are continually `inventive', acting and responding to themselves and each other. To grasp this is to understand `necessity' as not only the `mother', but also the `daughter' of invention. Quite clearly, the approach of a new millennium and the idea of sustainable development are both social constructions or `inventions'. They deal with the passage of time and exert a keen influence on those of us engaged in the quest to understand `accelerated environmental change', its causative factors, possible implications and necessary social responses. When new environmental realities emerge or are invented to challenge existing perceptions of nature/society or socioenvironmental relationships, we perceive the need to refashion our perceptions and invent new realities. Concern with the relationship between society and nature, prompted by our relatively recent perceptions of accelerated environmental change, has led both natural and social scientists to look for better ways of understanding their traditionally separate realms and this quest has led both to explore each other's territory and the `inventions' which inhabit them. This paper reflects briefly upon the history and philosophy of the social and natural sciences before turning its attention to some of the novel `inventions' that are currently coalescing in the field of environmental sociology and their resonance with some of those that are characteristic of a new, non-linear, chaotic ecology. The purpose of the piece is to explore the possibilities for developing mutual understanding between ecology and sociology, to assist us in our attempts to `deal with' accelerated environmental change and, also, to reflect upon the implications of our (re-)discovery, and converging appreciation, of the inextricable links between human societies and the ecosystems which they inhabit.
OPERATIONALIZING THE CONCEPT OF SUSTAINABILITY IN AGRICULTURE: ASSESSING THE PERFORMANCE OF AGROECOSYSTEMS ON MORE HIERARCHICAL LEVELS AND ACCORDING TO DIFFERENT PERSPECTIVES
A holistic evaluation of changes in agroecosystems needs a description of their effects on more hierarchical levels and valuations reflecting different perspectives (e.g. farmers; national economies; consumers; rural communities; ecological impact; dependency on fossil energy; biodiversity). Technological innovations in agriculture do not generate absolute "improvements" for everybody and/or on all space-time scales. Therefore, sustainability of agroecosystems has to do with discussing "trade-offs" rather than with searching "absolute improvements". In this paper we present a method of analysis characterizing the performance of agroecosystems in a multilevel and a multiperspective way (multidimensional AMOEBA approach). A given technical solution for agricultural production is described at different hierarchical levels (e.g. farm level, national economy level, ecological level) and by considering different available "valuations" of its effects. We argue that such an approach is particularly useful for the implementation of a sound processes of decision making about natural resource management in view of sustainability. In fact, it interfaces easily with multicriteria analysis (= parallel consideration of different indicators of performance referring to different scale and that cannot be collapsed into a single "cost/benefit" analysis), conflict management and participatory techniques (= involvement of different stake-holders with legitimate contrasting views of the same change in the process of decision making). In the AMOEBA approach, different sets of indicators are defined in terms of feasibility domains (range of values in which the system can still operate) and expectations of different actors. Biophysical links among changes occurring at different hierarchical levels are used to discuss possible scenarios. |