Myles Fisher

Earthworm communities in native savannas and man-made pastures of the Eastern Plains of Colombia

Abstract The structure and seasonal changes of earthworm communities were evaluated in a natural savanna and in a improved grass-legume pasture in a Colombian oxisol over a period of 18 months. One plot of 90×90 m was isolated in each of the systems and each month five samples of 1 m2×0.5 m and ten of 20×20×20 cm were randomly selected from a stratified block design. Species richness was similar in the two evaluated plots (seven species), whereas diversity measured by the index, H (Shannon and Weaver 1949) was clearly different, i.e. H=2.89 in natural savanna and H=1.29 in pasture. This is explained by differences in earthworm community structure. The average annual density in the savanna was 49.8, ranging from 10.8 to 135.8 individuals (ind) m–2, and biomass was 3.3 g m–2 (hand-sorting method), ranging from 0.9 to 11.5 g m–2. In the man-made pasture, density was 80.1 ind m–2 on average, ranging from 24 to 215.8 ind m–2 and biomass was more than tenfold higher, ranging from 29.2 to 110.4 g m–2. This was especially due to the presence of a large glossoscolecid anecic species, Martiodrilus carimaguensis Jiménez and Moreno, which has been greatly favoured by conversion of savanna to pasture. Endogeic species were dominant in the natural savanna whereas the anecic species accounted for 88% of total earthworm biomass in the pasture. Total earthworm density and biomass were significantly different in the two systems studied (t-test). The results indicate a clearly positive response of earthworm communities to improved pastures, a type of land use that is being increasingly adopted in moist neotropical savannas.

The nature and impact of climate change in the Challenge Program on Water and Food (CPWF) basins

In this article the authors assess the potential impacts of projected climate change on water, livelihoods and food security in the Basin Focal Projet basins. The authors consider expected change within the context of recently observed climate variability in the basins to better understand the potential impact of expected change and the options available for adaptation. They use multi-global circulation model climate projections for the AR4 SRES A2a scenario, downscaled and extracted for each basin. They find significant differences in the impacts (both positive and negative impacts) of climate change, between and within basins, but also find large-scale uncertainty between climate models in the impact that is projected.

Water, food and poverty: Global- and basin-scale analysis

Global population growth exerts stresses on river basins that provide food, water, energy and other ecosystem services. In some basins, evidence is emerging of failures to satisfy these demands. This paper assembles data from nine river basins in a framework that relates water and food systems to development. The framework provides a consistent basis for analysis of the water and food problem globally, while providing insight into specific conditions within basins. The authors find that successes occur when demand is met by increased productivity, while failure occurs when factors conspire to prevent development of land and water resources.

Water, food and livelihoods in river basins

Conflicting demands for food and water, exacerbated by increasing population, increase the risks of food insecurity, poverty and environmental damage in major river systems. Agriculture remains the predominant water user, but the linkage between water, agriculture and livelihoods is more complex than “water scarcity increases poverty”. The response of both agricultural and non-agricultural systems to increased pressure will affect livelihoods. Development will be constrained in closed basins if increased demand for irrigation deprives other users or if existing agricultural use constrains non-agricultural activities and in open basins if agriculture cannot feed an expanding or changing population or if the river system loses capacity due to degradation or over-exploitation.

Assessing the importance of livestock water use in basins

Recent concern over food prices has triggered a renewed interest in agricultural production systems. While attention is focused mainly on cropping, a complete analysis of food production systems should recognise the importance of livestock as major consumers of resources – in particular water – and as providers of food and other products and services. We propose that there is a need to examine not just food systems in isolation, but combined food and water systems, both of which are described as in a critical condition. From this broader perspective, it appears even more important to understand livestock systems because first, a total evaluation of agricultural water productivity – the gain from water consumed by agriculture – cannot be made without understanding the complexities of livestock-containing systems and; second, because in most tropical river basins, livestock systems are the major consumers of water. To identify total water productivity of livestock-containing systems, we describe concepts of agricultural water productivity and review the complexities of tracking the flow of water through livestock-containing systems: from inputs as evapotranspiration (ET) of forage and crops to outputs of valued animal products or services. For the second part, we present preliminary results from water use accounts analysis for several major river basins, which reveal that for Africa at least, livestock systems appear to be the major water consumers. Yet, little is known about the fate of water as it passes through these systems. We propose that livestock-containing systems offer substantial scope for increasing total water productivity and that there is considerable merit in improving the capacity to analyse water consumption and water productivity through such systems. Without removing this major source of uncertainty, the potential for systemic improvement to meet the world food and water crisis remains undefined and hence under-acknowledged.

Yields and water productivity of rainfed grain crops in the Volta Basin, West Africa

The observed water productivity (WP, kilograms of crop per cubic metre of rain) of cereals is very low in the Volta Basin: mean WP barely reaches 0.15 kg/m3 for maize (±0.05), with a mean yield of 1.25 t/ha (±0.58). We sought to explain these observations by using simulation modelling to develop a frequency analysis along a 9° transect on the meridian of Ouagadougou, that is about the whole gradient of rainfall in the basin. At both plot and basin scale, the model indicated that fertilizers would allow much higher yields and thus better WP.

Rainfall index insurance to help smallholder farmers manage drought risk.

The struggle to find sustainable formal insurance for droughts in developing countries captures the attention of many in the development community for good reason. Droughts disrupt the development process, and the impacts of drought are exacerbated by an unwillingness on the part of the poor to invest combined with a lack of access to credit. This paper first examines the problems associated with traditional approaches to formal drought insurance and goes on to examine the potential of index insurance that is event-driven. A combined weather-generation and crop simulation modelling approach is used to estimate site-specific risks. The method is demonstrated in a case study for dry bean production in Honduras.

Water availability and use across the Challenge Program on Water and Food (CPWF) basins

This paper analyses water availability and use within and between the Challenge Program on Water and Food basins. It describes the main features of water demand and supply in the basins and indicates where there are deficits and opportunities for development of water resources. A typology of basin water resources status uses a range of global spatial datasets. The main outcomes of basin activities on water availability are identified. Interbasin assessment of water availability is very challenging for such very large basins, due in large part to difficulties in collecting and integrating local data sets.

Institutions and organizations: The key to sustainable management of resources in river basins

Based on studies of water, poverty and livelihoods in nine river basins, this article reviews the role of institutions and organizations, focusing on their strengths and weaknesses, and to generalize as to why they fail to address the basin-wide issues of water, poverty and livelihoods. The authors show how a more comprehensive, integrated approach might change them to be more broadly relevant to basin-wide needs as well as to address the mismatch between development and the need to provide ecosystem services relevant to food, poverty, livelihoods and sustainable ecosystems.

Weather Indices for Designing Micro-Insurance Products for Small-Holder Farmers in the Tropics

Agriculture is inherently risky. Drought is a particularly troublesome hazard that has a documented adverse impact on agricultural development. A long history of decision-support tools have been developed to try and help farmers or policy makers manage risk. We offer site-specific drought insurance methodology as a significant addition to this process. Drought insurance works by encapsulating the best available scientific estimate of drought probability and severity at a site within a single number- the insurance premium, which is offered by insurers to insurable parties in a transparent risk-sharing agreement. The proposed method is demonstrated in a case study for dry beans in Nicaragua.