Carbohydrate supply limits invasion of natural communities by Argentine ants

The ability of species to invade new habitats is often limited by various biotic and physical factors or interactions between the two. Invasive ants, frequently associated with human activities, flourish in disturbed urban and agricultural environments. However, their ability to invade and establish in natural habitats is more variable. This is particularly so for the invasive Argentine ant (Linepithema humile). While biotic resistance and low soil moisture limits their invasion of natural habitats in some instances, the effect of food availability has been poorly explored. We conducted field experiments to determine if resource availability limits the spread and persistence of Argentine ants in remnant natural forest in North Carolina. Replicated transects paired with and without sucrose solution feeding stations were run from invaded urban edges into forest remnants and compared over time using baits and direct counts at feeding stations. Repeated under different timing regimes in 2006 and 2007, access to sucrose increased local Argentine ant abundances (1.6–2.5 fold) and facilitated their progression into the forest up to 73 ± 21% of 50-m transects. Resource removal caused an expected decrease in Argentine ant densities in 2006, in conjunction with their retreat to the urban/forest boundary. However, in 2007, Argentine ant numbers unexpectedly continued to increase in the absence of sugar stations, possibly through access to alternative resources or conditions not available the previous year such as honeydew-excreting Hemiptera. Our results showed that supplementing carbohydrate supply facilitates invasion of natural habitat by Argentine ants. This is particularly evident where Argentine ants continued to thrive following sugar station removal.     

Soil resources and their assessment

The assessment of the soil resource of any region has two parts, namely, an inventory of the kinds of soil and their distribution, and knowledge of the way each kind can be used and its performance under a range of circumstances. Soil varies substantially and intricately over short distances in most parts of the world. Inventory by field survey and air-photo interpretation must be done at a local scale. Inventories may be combined so that an individual nation state or region of similar size can know what kinds of soil it has, how much and where they are, how much each can produce, how to manage each in perpetuity, and the risks of degradation in use. Local classifications, with classes defined simply and identifiably on aerial photographs, will serve for mapping, and in combination with classical statistics can provide sound estimates from stratified sampling and agronomic experimentation.<br>Sound assessment should also be at this local scale initially. This should combine fundamental understanding of the soil''s behaviour, strategic agronomic research on regional stations, and on-farm trials. The last are crucial for estimating productivity of the soil in practice.<br>Data from all sources can be stored, sorted and displayed by geographic information systems that now have abundant capacity. They should be indexed by soil class and other attributes, with clear distinction being made between assessments of productive potential and basic data. They should be publicly accessible, to ensure that data are readily available and never lost.<br>Estimates of the soil resource and its productivity for large regions, nation states, and the world can be compiled from local surveys by sampling through a ''bottom-up'' procedure. <br>     

Use of woody plants by locals in Mare aux Hippopotames Biosphere Reserve in western Burkina Faso

The central area of the Mare aux Hippopotames Biosphere Reserve is located in the western part of Burkina Faso. Local populations have a close relationship with the reserve, from which they get much of their needs in food products, medicine, energy, arts and crafts. The use of resources has consequences for the biodiversity, ecosystem and environment of the reserve. The discussions held during ethnobotanical inquiries have permitted us to establish the main uses of woody plants and to pick out the repercussions of this usage. From this it emerges that the reserve has an important floristic richness and a biodiversity unknown to both locals and authorities.     

Introduction and conclusions for a Discussion entitled Land resources: on the edge of the Malthusian precipice?

Introduction and conclusions for a Discussion hosted by the Ciba Foundation and entitled Land resources: on the edge of the Malthusian precipice? Discussion held on the 4th and 5th December 1996, and organized and edited by D. J. Greenland, P. J. Gregory and P. H. Nye. <br>     

The environmental implications of intensified land use in developing countries

The major agricultural intensifications in the developed world over the last half century have produced a range of important environmental problems. These include pollution, damage to wildlife and landscape and other issues, both on- and off-site. These are largely being controlled by scientific investigation and Government regulation. As developing countries increase agricultural production over the next 30 years, this may also cause even more serious environmental damage.<br>The paper distinguishes between production-related on-site damage, and off-site and more extensive effects. Both may involve soil and water effects, such as soil erosion, salinization, siltation, eutrophication and loss of water quality. The use of more agrochemicals can damage water quality, health, wildlife and biodiversity. Loss of habitat from the extension of farming is particularly damaging to biodiversity. A developing off-site problem is the production of greenhouse gases by farming systems, including the conversion of forests to farmland. In the future the introduction of genetically engineered species of plants, animals or microbes will need secure control.<br>Work, probably on a catchment basis, is necessary to understand and control these problems. The three main requirements are much better environmental information from the developing world; the selection of environmental indicators to be monitored; and the support of local farmers in protecting the environment. There are encouraging indications of farmer concern and action over obvious on-site damage, but this may not extend to extensive off-site issues. The main danger is that developing food scarcity would cause the environmental issues to be ignored in a race for production. <br>