Grade 9 Science notes
Chapter 4 – Ecosystems by Design
4.7 The Urban Ecosystem
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Cities are major sources of air and water pollution
Air pollution is caused by car exhaust, burning of fuels, and gases from
factories
Water pollution comes from biological, commercial, and industrial wastes
Differences between Urban and Natural Ecosystems
Feature
Urban Ecosystem
Surface features Dominated by buildings, paved
roads, parking areas
Plant species
Not very many plants
Mostly non-native grasses
Animal species
Dogs, cats, house mice, rats,
pigeons, starlings, sparrows – all
non-native
Flow of materials Human body wastes collected
and disposed in surrounding
environment
Minimal recycling and compost
Food webs
Dependent on importing food
from outside agroecosystems
Sustainability
Cannot be sustained without
other ecosystems
Natural Ecosystem
Dominated by plants
Many native plants
Many native species
Natural nutrient cycles
Complex natural food webs
Sustainable on its own
Unlike organisms in a natural ecosystem, humans in an urban setting rely on outside
ecosystems
Greener Cities
 City planners and politicians are beginning to develop strategies to make
cities more sustainable
 Community composting programs
 Improve public transit
 Ban the use of pesticides
 Enhance green spaces within cities
 Promote shop locally campaigns