July 15, 2011 Science Magazine
Trophic Downgrading of Planet Earth

[Extensive biology omitted, below are the abstract and three excellent graphics and notes.]
Until recently, large apex consumers were ubiquitous across the globe and had been for millions of years. The loss of these animals may be humankind’s most pervasive influence on nature. Although such losses are widely viewed as an ethical and aesthetic problem, recent research reveals extensive cascading effects of their disappearance in marine, terrestrial, and freshwater ecosystems worldwide. This empirical work supports long-standing theory about the role of top-down forcing in ecosystems but also highlights the unanticipated impacts of trophic cascades on processes as diverse as the dynamics of disease, wildfire, carbon sequestration, invasive species, and biogeochemical cycles. These findings emphasize the urgent need for interdisciplinary research to forecast the effects of trophic downgrading on process, function, and resilience in global ecosystems.

[The article from The Week magazine immediately following below seemed appropriate introduction for the graphics from the more biology-heavy Science magazine artical of primary interest here.

August 5, 2011 The Week Magazine
Health & Science
The bloody fang and the food chain

The disappearance of predators like wolves, lions, and sharks is having a disastrous impact on global ecosystems, scientists say. Until now, conservation efforts have largely focused on saving entire habitats, but a new international survey shows that in terms of their ecological impact, “all species aren’t created equal,” Peter Kareiva, chief scientist at the Nature Conservancy, tells DiscoveryNews.com. “You may hate wolves,” says study co-author Ellen K. Pikitch of Stony Brook University. “But without them, the land changes.” The decimation of North America’s wolf population, she says, has not only allowed elk and deer to suppress willows and other trees, but also to more readily carry ticks—and the Lyme disease they spread—into human contact. On the Atlantic coast, fewer sharks mean more cownose rays, which in turn have been able to feast too freely on the now-threatened Chesapeake Bay oyster. Kareiva says the findings suggest that instead of “blindly protecting all species,” we should focus on the “apex consumers” at the top of the food chain, which are currently disappearing even faster than other animals because they need more space to roam and more time to reproduce.

Fig. 1 Landscape-level effects of trophic cascades from five selected freshwater and marine ecosystems. (A) Shallow seafloor community at Amchitka Island (Aleutian archipelago) before (1971; photo credit: P. K. Dayton) and after (2009) the collapse of sea otter populations. Sea otters enhance kelp abundance (right) by limiting herbivorous sea urchins (left) (20). (B) A plot in the rocky intertidal zone of central California before (September 2001, right) and after (August 2003, left) seastar (Pisaster ochraceous) exclusion. Pisaster increases species diversity by preventing competitive dominance of mussels. [Photo credits: D. Hart] (C) Long Lake (Michigan) with largemouth bass present (right) and experimentally removed (left). Bass indirectly reduce phytoplankton (thereby increasing water clarity) by limiting smaller zooplanktivorous fishes, thus causing zooplankton to increase and phytoplankton to decline (26). (D) Coral reef ecosystems of uninhabited Jarvis Island (right, unfished) and neighboring Kiritimati Island (left, with an active reef fishery). Fishing alters the patterns of predation and herbivory, leading to shifted benthic dynamics, with the competitive advantage of reef-building corals and coralline algae diminished in concert with removal of large fish (66). (E) Pools in Brier Creek, a prairie margin stream in south- central Oklahoma with (right) and lacking (left) largemouth and spotted bass. The predatory bass extirpate herbivorous minnows, promoting the growth of benthic algae (67).
Fig. 2 Landscape-level effects of trophic cascades from four terrestrial ecosystems. (A) Upland habitat of islands with (right) and without (left) Arctic foxes in the Aleutian archipelago. Foxes drive terrestrial ecosystems from grasslands to tundra by limiting seabirds and thereby reducing nutrient inputs from sea to land (47). (B) Venezuelan forests on small islands of Lago Guri (left: jaguar, cougar, and harpy eagles absent) and mainland forest (right, predators present). A diverse herbivore guild erupted with the loss of predators from the island, thereby reducing plant recruitment and survival (68). (C) Riparian habitat near the confluence of Soda Butte Creek with the Lamar River (Yellowstone National Park) illustrating the stature of willow plants during suppression (left, 1997) from long-term elk browsing and their release from elk browsing (right, 2001) after wolf reintroductions of 1995 and 1996 (25). (D) Decline of woody vegetation in Serengeti after eradication of rinderpest (by early 1960s) and the recovery of native ungulates (by middle 1980s). Left, 1986; right, 2003 (69).

Fig. 1

Fig. 2
Fig. 4 Examples of the indirect effects of apex consumers and top-down forcing on diverse ecosystem processes, including wildfires (30); disease (35); composition of atmosphere (37), soil (47), and fresh water (49); invadability by exotic species (55); and species diversity (60). Interaction web linkages by which these processes are connected to apex consumers are shown in the center. Magnitude of effect is shown in graphs on right. Blue bars are data from systems containing the apex consumer; brown bars are data from systems lacking the apex consumer. Data replotted from original sources (cited above), except raw data on native bird diversity in chaparral habitats provided by K. Crooks.

Fig. 4

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