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For a number of interventions or pressure factors in the Trend scenario, the impacts on the biodiversity intactness in aquatic ecosystems have been estimated: wetland conversion, impacts of land use in river catchments including pollution by nutrients (eutrophication) and major hydrological changes (Janse et al., 2015). According to the model, this will result in a considerable further decrease of (world-averaged) aquatic biodiversity intactness (Figure 1), the major decreases to be expected in Africa, Latin-America and parts of Asia. Subsequently, the three development pathways show different reductions in biodiversity intactness (Figure 1). The pathways have different impacts across regions and none of these are beneficial for all aspects of biodiversity in all regions of the world. The options incorporated in each of the three pathways are denoted with an asterisk (*) in Table 2. These are mainly related to land use, water use and pollution reduction. Other nature-based solutions for water management can be envisaged that reduce the pressures on aquatic ecosystems, such as catchment management and different hydropower options, but these were not yet included in the current model analysis (which was restricted to broad-scale developments, as explained before). Their potential, however, is discussed in the sections below.
Table 2.

Overview of challenges and options per sub-sector.

CitiesWater for foodHydropowerFlood protection
Main challenge Clean water supply
Waste disposal 
Water shortage Reliable low-silt flows Vulnerable cities 
Main impact Pollution through wastewater High water abstraction
Pollution through nutrients and agrochemicals 
Disruption of rivers Disruption of rivers 
Nature-based options 
 GT Improved water and waste treatment (*) Improved resource efficiency(*)
Genetic engineering 
Regulatory installations – 
 DS  Catchment protection
Wastewater reuse 
Multipurpose agroecosystems (*) Alternative locations
Watershed management 
Natural infrastructure 
 CC Waste prevention (*) Reduced demand for animal products (*) Alternative energy sources – 
CitiesWater for foodHydropowerFlood protection
Main challenge Clean water supply
Waste disposal 
Water shortage Reliable low-silt flows Vulnerable cities 
Main impact Pollution through wastewater High water abstraction
Pollution through nutrients and agrochemicals 
Disruption of rivers Disruption of rivers 
Nature-based options 
 GT Improved water and waste treatment (*) Improved resource efficiency(*)
Genetic engineering 
Regulatory installations – 
 DS  Catchment protection
Wastewater reuse 
Multipurpose agroecosystems (*) Alternative locations
Watershed management 
Natural infrastructure 
 CC Waste prevention (*) Reduced demand for animal products (*) Alternative energy sources – 

(*) These options are included in the modelling of the pathways as shown in Figure 1.

Fig. 1.

Pressures driving global-averaged freshwater biodiversity loss under the Trend scenario (2050) and three development pathways (GT: global technology, DS: decentralised solutions, CC: consumption change). Source: PBL (Kok et al., 2014).

Fig. 1.

Pressures driving global-averaged freshwater biodiversity loss under the Trend scenario (2050) and three development pathways (GT: global technology, DS: decentralised solutions, CC: consumption change). Source: PBL (Kok et al., 2014).

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