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- Klintenberg, Patrik
(författare)
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More Water, Less Grass? : An assessment of resource degradation and stakeholders’ perceptions of environmental change in Ombuga Grassland, Northern Namibia
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The objectives of this thesis are to assess: to what degree have natural resources deteriorated in a grazing area in northern Namibia, how do perceptions of environmental change held by local stakeholders there, correspond to scientific assessments, and how do these relate to national estimates? Analysis of the process of developing national indicators for monitoring of land degradation concluded that specific indicators should be developed on national level, and in some instances even on local level as there are no universal causes of land degradation. According to farmers overgrazing and low rainfall since the early 1990s cause negative environmental changes in the study area, partly confirming findings from national monitoring. Results also suggest that: less grazing outside the study area, improved access, permanent water supply, and fencing of large areas, also contributed. Results show that improved water supply was the most important factor. Investigation of the influence of permanent water points on grazing resources showed that perennial grasses are replaced by less palatable annual grasses as far as 6 km from water points along a water pipeline. No significant grazing induced changes in grass composition were observed around privately owned wells. Private ownership seems to be a key factor preventing over-utilization of grazing resources around the latter. A remote sensing study using Landsat TM imagery identified bare ground, saltpans and grassland with a fair accuracy. Separation of woodland from shrubland and shrubland from grassland was less accurate using supervised classification. The results show that the soil adjusted vegetation index provides valuable information about variations of green biomass over time in semi-arid environments. However, it is suggested that satellite based investigations should be supported by thorough ground based assessment due to the influence of underlying soil in this environment.
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- Abbadini, Marco, et al.
(författare)
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DUALITY FOR COALGEBRAS FOR VIETORIS AND MONADICITY
- 2024
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Ingår i: Journal of Symbolic Logic (JSL). - 0022-4812 .- 1943-5886.
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Tidskriftsartikel (refereegranskat)abstract
- We prove that the opposite of the category of coalgebras for the Vietoris endofunctor on the category of compact Hausdorff spaces is monadic over $\mathsf {Set}$ . We deliver an analogous result for the upper, lower, and convex Vietoris endofunctors acting on the category of stably compact spaces. We provide axiomatizations of the associated (infinitary) varieties. This can be seen as a version of Jonsson-Tarski duality for modal algebras beyond the zero-dimensional setting.
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