Ecosystem Services - Ecological Systems - page 82

ecosystems from one type to another is often motivated by a desire for a different
set of ES, though consideration of the services of the two systems and their tradeoffs
is often incomplete.
Ecosystem Services Across Systems
A wide range of ES is generated in the terrestrial realm, by croplands, natural and
managed forests, grasslands, and wetlands. In each of these systems, for example,
vegetation can protect and enhance soils, preventing their loss through erosion and
improving fertility by retaining moisture and storing and recycling nutrients. Vege-
tation and soils together regulate the quantity, quality, and timing of water flows, thus
moderating floods and droughts and providing cleaner, more reliable supplies [ 8 ].
Forests stand out as important in regulating water and carbon cycles [ 30 ]; in their
strong influence on local, regional, and global climate [ 30 , 49 ]; and because of the
multiple, interacting threats to their future (e.g., [ 44 , 66 ]). They also provide natural
products for subsistence use or sale including timber, firewood, mushrooms, fruits
and seeds, medicinal plants, rubber, cork, and bushmeat. Forest and woodland
habitats harbor species that provide pollination and pest control to commercial or
subsistence crops. Grassland and other dryland systems play these same critical
roles in addition to supporting vast livestock populations [ 38 ]. Wetlands occupy
a small fraction of Earth's surface, but dominate the landscape where they are
concentrated and provide a wide array of water quality, flood mitigation, coastal
protection, and biogeochemical services [ 38 ]. Each of these systems, however
natural or managed, can provide habitat for biodiversity and opportunities for
recreational activities, spiritual experiences, and creative, cultural expression.
Freshwater ecosystems provide a suite of highly visible and widely appreciated
ES [ 53 ]. The freshwater regulated by terrestrial systems and the atmosphere is used
for drinking, hydropower production, irrigation, household activities (washing,
etc.), industrial purposes (cooling, manufacturing, etc.), and cultural experiences.
People also gain large revenues and nutrition from freshwater fisheries and aqua-
culture. Less appreciated is the value of sediment transport and deposition in rivers
that supply river reaches and downstream beaches with important sand and gravel
resources. Wetlands and other aquatic vegetation can regulate flood waters and
cycle nutrients, improving water quality. Finally, freshwater systems serve as
pathways for human transportation and recreational or cultural activities.
Marine ecosystems also provide all four classes of ecosystem services
described in the MA. Marine fisheries and aquaculture provide nutrition, feed for
animals, livelihoods, and important recreational and cultural opportunities.
Harvests of other species for food additives, cosmetics, and pharmaceuticals also
support health, nutrition, and livelihoods. Marine biogenic habitats (such as
coral reefs, oyster reefs, and kelp forests) regulate natural hazards including
storm surges, and may play a critical role in helping coastal communities adapt
to sea level rise. Marine systems also transform, detoxify, and sequester wastes.