Cleanup of fractured rock aquifers. II. Effects of matrix diffusion and nonaqueous phase liquid

Model calculations are used to explore the effects of the kinetics of diffusion of dissolved organic compounds into and out of low-permeability porous materials and of the rate of solution of nonaqueous phase liquid (NAPL) droplets (into the aqueous phase) on the rate of cleanup of contaminated aquifers. Two models are presented: (1) the flushing of organic compounds initially distributed as NAPL droplets in a fracture in a porous rock aquifer, and (2) the removal of organic compounds initially present as NAPL in an aquifer containing low-permeability porous clay lenses. NAPL droplet size is found to be of much less importance than the spacing of the fractures in the porous rock in the first model or the thickness of the clay lenses in the second.     

The livestock revolution, food safety, and small-scale farmers: why they matter to us all

Global consumption, production, and trade of livestock products have increased rapidly in the last two decades and are expected to continue. At the same time, safety concerns regarding human and animal disease associated with livestock products are increasing. Efforts to increase public health safety standards aimed at legitimately reducing the risks of human and animal disease have focused internationally on standards to regulate the movement of livestock products. There is concern, though, that measures to regulate these standards internationally, such as the WTO SPS measures that in part aim to open international markets, may marginalize small-scale poor producers. The cycle of poverty they are trying to escape through livestock production may, in fact, widen, leading to increased global poverty, malnutrition, and disease. Developing and developed nations alike should be concerned with public and private efforts to address appropriate food safety policies to reduce the likelihood of this effect. Analysis of the impact on small-scale livestock farmers is needed, as well as solutions that consider joint public and private sector initiatives. Costly farm to table tracking systems are not an option, but locally orchestrated vertically integrated systems may have merit in reducing food safety risks and in providing small-scale farmers with increased access to markets, locally and internationally. Increased scientific and technical capacity, and training of WTO officials from developing nations is also needed.     

Reducing visitors' group size increases the number of birds during educational activities: Implications for management of nature-based recreation

Organized tours to watch wildlife are popular recreational and educational activities, in which the visitor expectative (to observe as many and as diverse animals as possible) runs parallel to conservation purposes. However, the presence of visitors may cause negative impacts on wildlife, which makes recreation difficult to manage. Thus, restricting visitor's load to minimize impacts on fauna may be advisable, but too much restriction may end up disappointing the public. We analysed how visitors' group size influences the number and variety of birds observed during an educational activity directed to scholars, in a forested area where public access is otherwise restricted. We observed fewer birds, but not fewer species, as the size of scholars' groups increased. Such effect was apparently mediated by a few species demonstrating reduced tolerance to increased group size. Our results support the idea that reducing the size of visitors' groups not only helps to minimize the negative impacts on wildlife derived from leisure activities, but also allows visitors to watch more wildlife. Therefore, organizing visitors in small numbers is recommended in the design of activities directed to groups of people visiting natural areas.