Applications from food web and ecosystem theory - Ecological Applications: Toward a Sustainable World - page 242

understand that human pressures alter the way energy and nutrients fl ow through ecosystems -
restoration should take this into account
realize that the most damaging invaders are often those that upset energy and nutrient dynamics
recognize that when agricultural fertilizers are wastefully applied, they pollute the waterways that
drain the land
appreciate that ecosystems provide people with many valuable services (such as forest products,
fi s h , crop pollination and climate control)
understand that managers need indicators of ecosystem health to help them identify ecosystems
in trouble

9.1 Introduction Aretha had been spending as much time as possible in the outdoors and was enjoy-

ing her retirement after a lifetime in banking. She considered herself a lucky indi-
vidual until she was involved in two events in quick succession, one personal and
the other witnessed by millions around the world. ' A few weeks after hiking along a
woodland trail, one side of my face became partially paralyzed. Then a little later I
developed painful bouts of arthritis in my knees. ' Aretha's physician ran some tests
and diagnosed Lyme disease, an infection spread by ticks and picked up as she
walked through the forest. Antibiotics killed the bacteria responsible but a feeling
of lethargy persisted, so Aretha decided to take a holiday in Thailand. The sun and
sea were doing the trick until the coast was struck by a dreadful tsunami (tidal
wave). ' I still have nightmares, plagued by images of the people who were crushed and
drowned while I watched helplessly from my hotel on the hill. ' It hardly bears thinking
about.
This chapter is concerned, like the last, with the community level of organization,
focusing on the food webs that link species together. Studies that unravel the
complex interactions in food webs can provide key information to managers on
issues as diverse as minimizing human disease risk (such as Aretha's Lyme disease
- Section 9.2), managing harvests (Section 9.3) and planning conservation measures
(Section 9.4). When communities are considered in their physicochemical setting,
we move to the ecosystem level of organization - and the focus then is on the way
energy and matter pass through the food web. Coupled with an understanding of
food web theory, this ecosystem approach has much to offer managers when they
confront invasions (Section 9.5), plan restoration strategies (Section 9.6), design
sustainable agroecosystems and remedy the effects of excess nutrients leaking into
waterways (Section 9.7). The theory relating to food webs, and the way that energy
and nutrients move through them, is summarized in Box 9.1. For more detailed
treatments check out Begon et al. (2006).
Ecosystems provide people with many valuable services (Section 9.8.1). You have
already come across some relatively straightforward ecosystem services, including
crop pollination by wild bees that inhabit forest fragments (Section 4.5.4) and the
disposal of dead bodies by vultures in India (Section 5.1). More sur pr i sing are serv-
ices such as the protection against tsunamis provided by intact offshore coral reefs
- these absorb some of the wave's power. According to the American Geophysical
Union, illegal coral mining off the southwest coast of Sri Lanka allowed far more
onshore destruction from the recent Pacifi c-wide tsunami than occurred in nearby
areas whose coral reefs were intact. You saw in Section 1.2.2 that ecosystem services
can be divided into several categories. Here it is evident that exploitation of a pro-