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- Albert, James S., et al.
(författare)
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Scientists' warning to humanity on the freshwater biodiversity crisis
- 2021
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 50, s. 85-94
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Tidskriftsartikel (refereegranskat)abstract
- Freshwater ecosystems provide irreplaceable services for both nature and society. The quality and quantity of freshwater affect biogeochemical processes and ecological dynamics that determine biodiversity, ecosystem productivity, and human health and welfare at local, regional and global scales. Freshwater ecosystems and their associated riparian habitats are amongst the most biologically diverse on Earth, and have inestimable economic, health, cultural, scientific and educational values. Yet human impacts to lakes, rivers, streams, wetlands and groundwater are dramatically reducing biodiversity and robbing critical natural resources and services from current and future generations. Freshwater biodiversity is declining rapidly on every continent and in every major river basin on Earth, and this degradation is occurring more rapidly than in terrestrial ecosystems. Currently, about one third of all global freshwater discharges pass through human agricultural, industrial or urban infrastructure. About one fifth of the Earth's arable land is now already equipped for irrigation, including all the most productive lands, and this proportion is projected to surpass one third by midcentury to feed the rapidly expanding populations of humans and commensal species, especially poultry and ruminant livestock. Less than one fifth of the world's preindustrial freshwater wetlands remain, and this proportion is projected to decline to under one tenth by midcentury, with imminent threats from water transfer megaprojects in Brazil and India, and coastal wetland drainage megaprojects in China. The Living Planet Index for freshwater vertebrate populations has declined to just one third that of 1970, and is projected to sink below one fifth by midcentury. A linear model of global economic expansion yields the chilling prediction that human utilization of critical freshwater resources will approach one half of the Earth's total capacity by midcentury. Although the magnitude and growth of the human freshwater footprint are greater than is generally understood by policy makers, the news media, or the general public, slowing and reversing dramatic losses of freshwater species and ecosystems is still possible. We recommend a set of urgent policy actions that promote clean water, conserve watershed services, and restore freshwater ecosystems and their vital services. Effective management of freshwater resources and ecosystems must be ranked amongst humanity's highest priorities.
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| 3. |
- Oksanen, Tarja, et al.
(författare)
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The impact of thermal seasonality on terrestrial endotherm food web dynamics : a revision of the Exploitation Ecosystem Hypothesis
- 2020
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Ingår i: Ecography. - : John Wiley & Sons. - 0906-7590 .- 1600-0587. ; 43:12, s. 1859-1877
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Tidskriftsartikel (refereegranskat)abstract
- Many terrestrial endotherm food webs constitute three trophic level cascades. Others have two trophic level dynamics (food limited herbivores; plants adapted to tackle intense herbivory) or one trophic level dynamic (herbivorous endotherms absent, thus plants compete for the few places where they can survive and grow). According to the Exploitation Ecosystems Hypothesis (EEH), these contrasting dynamics are consequences of differences in primary productivity. The productivity thresholds for changing food web dynamics were assumed to be global constants. We challenged this assumption and found that several model parameters are sensitive to the contrast between persistently warm and seasonally cold climates. In persistently warm environments, three trophic level dynamics can be expected to prevail almost everywhere, save the most extreme deserts. We revised EEH accordingly and tested it by compiling direct evidence of three and two trophic level dynamics and by studying the global distribution of felids. In seasonally cold environments, we found evidence for three trophic level dynamics only in productive ecosystems, while evidence for two trophic level dynamics appeared in ecosystems with low primary productivity. In persistently warm environments, we found evidence for three trophic level dynamics in all types of ecosystems. The distribution of felids corroborated these results. The empirical evidence thus indicates that two trophic level dynamics, as defined by EEH, are restricted to seasonally cold biomes with low primary productivity, such as the artic-alpine tundra and the temperate steppe.
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