15 6Nature, food, and water
Thus water degradation due to sedimentation, agricultural chemicals, and
solar heating is probably widespread across urban regions. Where fields are
irrigated in dry climates, water tables are often lowered and streamflow much
reduced. Ecologically effective vegetated stream corridors are likely to be few
and fragmented.
Reestablishing the stream corridors with attached patches of natural vegeta-
tion, especially upstream of the city or far downstream, is particularly valuable.
Reducing agricultural inputs to streams and rivers, both by fine-scale land-use
changes and farming practices, is also valuable.
[W2]Only a fifth of the regions has >80 % natural vegetation cover around rivers and
major streams, while another fifth has 40--70 % natural cover(Figure6.11).
In the former case, relatively good overall water quality, aquatic ecosystems,
and fish populations are likely to be present over major portions of the region. In
thelatter case, stream and river degradation is probably widespread, but some
high-water-quality streams and rivers exist in the region, which can serve as
valuable species sources for rapid restoration. Reestablishing ecologically effec-
tive vegetated stream corridors to help reconnect high-water-quality streams and
rivers is apriority.
[W3]Cropland is the predominant human land use around rivers and major streams in
almost all urban regions(Figure6.11).
Food products for the nearby city and viable farming communities and
economies are real benefits that often need emphasis. Farmland species are
well established. The widespread cropland also means extensive warm water,
soil erosion, muddy water, sediment-covered bottoms, degraded fish habitat,
and agricultural chemicals, including varied pesticides and nitrogen/phosphorus
from fertilizer. A variety of improvements can be made. Better fine-scale farming
practices and land uses would help. Future outward development should avoid
degrading streams and rivers, as well as disrupting large prime-agricultural-soil
areas.
[W4]Considerable built area (10--40 % land cover) surrounds rivers and major streams in
40 % of the regions(Figure6.11).
Consequently, urban runoff and human impacts are likely to be widespread.
Various solutions include relocating (often old) industries away from the
stream/riverside to industrial parks with efficient water, power, and waste-
disposal availability. Increase the length and width of vegetated stream/river
corridors. Limit future outward development to sites adjacent to existing built
areas.