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51.
Sandra Uthes Katharina Fricke Peter Zander Stefan Sieber Annette Piorr 《Ecological modelling》2010,221(18):2136-2152
The Common Agricultural Policy (CAP), a system of market support instruments, direct income transfers, and rural development measures, has been put through an ongoing reform process in recent decades. This paper introduces three policy impact assessment tools (SIAT, SEAMLESS-IF, MEA-Scope tool) and analyses how these tools have responded to a number of challenges for integrated assessment modelling as reported in the international literature. Significant progress has been made with regard to modelling linkages whereas other challenges, particularly those related to issues of scale and uncertainty management, require further efforts. It is also analysed which CAP instruments are represented and what kinds of effects can be analysed at different scales. Market instruments and direct payments are comparatively well represented, while the ability to model rural development measures is mostly beyond the scope of these tools. Because each tool has found a different solution for coping with the common challenges of integrated assessment modelling, the choice of one of the tools for a particular application depends strongly on the policy questions being asked. The SIAT provides the big picture via its ability to represent broad changes in policy instruments with EU-wide cross-sector impacts. The most comprehensive analysis of agricultural policy instruments can be obtained with SEAMLESS-IF. The MEA-Scope tool complements the other two approaches with detailed regional profiles. 相似文献
52.
Anna Bateman Dan van der Horst David Boardman Arun Kansal Cynthia Carliell-Marquet 《Resources, Conservation and Recycling》2011,55(12):1146-1153
Every year 90 million tonnes of housed livestock manures are produced in the UK. This is a valuable reservoir of global phosphorus (P) and a point in the cycle where it is vulnerable to being lost from the terrestrial system. Improved manure management for the effective reuse of phosphorus is vital to simultaneously tackle a major source of water pollution and reduce our dependence on imported fertilisers. This paper quantifies, for the first time, the spatial and temporal challenges of recycling the required amount of manure P from areas of livestock production to areas of crop production in eight regions of England. The analysis shows that England has a P deficit and therefore the capacity to fully utilise the manure P on arable land, but that uneven spatial distribution of livestock poses a significant challenge to closing the P loop in agriculture. Two of the eight regions were shown to have surplus manure P, with the remaining six regions having P deficits, indicating that an annual export of 4.7 thousand tonnes P (2.8 million tonnes manure) must take place from the west to the east of the country each year to balance P supply and demand. Moreover, housed manure production peaks between October and February, requiring an excess of 23.0 thousand tonnes P (15 million tonnes manure) to be stored until it can be used for crop fertilisation from March onwards. The results demonstrate the scale of the challenge in managing manure P in an agricultural system that has separated livestock production from crop production, a pattern that is echoed throughout the developed world. To overcome the spatial and temporal challenges, a logistical system is recommended that will balance the nutrient potential (nitrogen and P content and availability) and pollution potential (eutrophication, greenhouse gas emissions, particulates and nitrous oxide from transport) for cost-effective and environmentally compatible redistribution of manure P from areas of surplus to areas of deficit, when required. 相似文献
53.
One concept of evolutionary ecology holds that a living fossil is the result of past evolutionary events, and is adapted
to recent selective forces only if they are similar to the selective forces in the past. We describe the present environment
of the living coelacanth Latimeria chalumnae Smith, 1939 at Grande Comore, western Indian Ocean and report depth-dependent cave distribution, temperature, salinity and
oxygen values which are compared to the fish's distribution and its physiological demands. We studied the activity pattern,
feeding behaviour, prey abundance and hunting success to evaluate possible links between environmental conditions, feeding
ecology and evolutionary success of this ancient fish. Transmitter tracking experiments indicate nocturnal activity of the
piscivorous predator which hunts between approximately 200 m below the surface to 500 m depth. Fish and prey density were
measured between 200 and 400 m, both increase with depth. Feeding tracks and feeding strikes of the coelacanth at various
depths were simulated with the help of video and laser techniques. Along a 9447 m video transect a total of 31 potential feeding
strikes occurred. Assuming 100% hunting success, medium-sized individuals would obtain 122 g and large females 299 g of prey.
Estimates of metabolic rates revealed for females 3.7 ml O2 kg−1 h−1 and for males 4.5 ml O2 kg−1 h−1. Today coelacanths are considered to be a specialist deep-water form and to inhabit, with their ancient morphology, a contemporary
environment where they compete with advanced, modern fish.
Received: 5 July 1999 / Accepted: 11 November 1999 相似文献
54.
Acoustic telemetry was used to examine patterns of activity and space utilisation of coelacanths, nocturnal predators which
spend the day in submarine caves. Nine coelacanths (Latimeria chalumnae) were tracked, each for a period of 1 to 16 nights at Grande Comore, West Indian Ocean. Activities lasted on average 9 h,
usually starting shortly after sunset and ending before sunrise. Vertically, coelacanths moved up and down at and below cave
level by following the bottom contour, mainly between 180 and 400 m depth. The deepest record was 698 m, the shallowest 133 m.
Most time was spent between 200 and 300 m depth. Large individuals performed deep excursions to depths below 400 m, usually
once per night. The fish spent most time in water temperatures of 15 to 19 °C; they rarely ventured into waters warmer than
22 °C measured at depths shallower than 160 m depth. Horizontally, coelacanths stayed in narrow areas ranging from <1 to 10 km
of coastline. Coelacanths are extremely slow drift-hunters with an estimated average swimming speed of 3.2 m min−1, often travelling not more than 3 km per night. They probably take advantage of local upwelling and downwelling and slow
currents occurring parallel to the steep slopes. This study shows that coelacanths are inhabitants of the subphotic zone,
where they are active mainly below the depth of their daytime refuges.
Received: 7 July 1999 / Accepted: 11 February 2000 相似文献
55.
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57.
Horst Bartels 《Die Naturwissenschaften》1957,44(22):595-596
58.
59.
The Science of Nature - 相似文献
60.