Day Length Period of time for a location on the Earth when insolation from the Sun is being received. Daylight Savings Time The setting of time so it is one hour ahead starting in the spring and one hour back beginning in the fall in the Northern Hemisphere. In Canada and the United States the dates for these events is the first Sunday in April spring ahead and the last Sunday in October fall back. Debris Flow A type of mass movement where there is a downslope flow of a saturated mass of soilsedimentand rock debris.
Historically, habitat and land use change have had the biggest impact on biodiversity across biomes. Climate change is projected to increasingly affect all aspects of biodiversity, from individual organisms, through populations and speciesto ecosystem composition and function.
Pollution, especially the deposition of nitrogen and phosphorus, but also including the impact of other contaminants, is also expected to have an increasing impact, leading to declining biodiversity across biomes.
Overexploitation and invasive species have been important as well and continue to be major drivers of changes in biodiversity C4. Only biomes relatively unsuited to crop plants, such as deserts, boreal forests, and tundra, are relatively intact C4.
Deforestation and forest degradation are currently more extensive in the tropics than in the rest of the world, although data on boreal forests are especially limited C A study of the southern African biota shows how degradation of habitats led to loss of biodiversity across all taxa.
For marine ecosystemsthe most important direct driver of change in the past 50 years, in the aggregate, has been fishing. Fishing is the major direct anthropogenic force affecting the structure, function, and biodiversity of the oceans C In these areas a number of targeted stocks in all oceans have collapsed—having been overfished or fished above their maximum sustainable levels.
Recent studies have demonstrated that global fisheries landings peaked in the late s and are now declining despite increasing effort and fishing power, with little evidence of this trend reversing under current practices C In addition to the landings, the average trophic level of global landings is declining, which implies that we are increasingly relying on fish that originate from the lower part of marine food webs C However, the accuracy of this figure has not been established due to an absence of reliable data C Massive changes have been made in water regimes.
Water withdrawals from rivers and lakes for irrigation or urban or industrial use increased sixfold since C7. The introduction of non-native invasive species is now a major cause of species extinction in freshwater systems.
It is well established that the increased discharge of nutrients causes intensive eutrophication and potentially high levels of nitrate in drinking water and that pollution from point sources such as mining has had devastating impacts on the biota of inland waters C22 Jul Americans came up with 36 answers to a Gallup poll asking the biggest problem currently facing the country, and no one answered “climate change,” with only two percent even mentioning the environment at all, Gallup revealed last week.
Declination Location () on the Earth where the Sun on a particular day is directly overhead (90° from horizon) at solar ashio-midori.com location is somewhere between ° North and ° South depending on the time of the year.
Desertification is a type of land degradation in which a relatively dry area of land becomes increasingly arid, typically losing its bodies of water as well as vegetation and wildlife. It is caused by a variety of factors, such as through climate change (particularly the current global warming) and through the overexploitation of soil through human activity.
v Acknowledgements The United Nations Economic Commission for Africa (ECA) wishes to acknowledge the invaluable contributions by the Member States, and partners at regional and subregional levels.
Biodiversity change is caused by a range of drivers.A driver is any natural or human-induced factor that directly or indirectly causes a change in an ecosystem. A direct driver unequivocally influences ecosystem ashio-midori.com indirect driver operates more diffusely, by altering one or more direct ashio-midori.comant direct drivers affecting biodiversity are habitat change, climate change.
Desertification: Desertification, the process by which natural or human causes reduce the biological productivity of drylands (arid and semiarid lands).
Declines in productivity may be the result of climate change, deforestation, overgrazing, poverty, political instability, unsustainable irrigation practices, or.