a blackhole binary
LETTERS I BOOKS I POLICY FORUM I EDUCATIONFORUM I PERSPECTIVES
edited by Jennifer Sills
Recognizing Conservation Success
IN THE NEWS FOCUS STORY “EMBRACING INVASIVES” (18 MARCH, P. 1383), G. VINCE PORTRAYS
a failed policy aimed solely at maintaining pristine ecosystems. The story lacks context.
Conservationists do not follow an impossible “pristine dream”; in most areas, they deal with
modified ecosystems and have long recognized the challenges of managing “novel ecosystems.”
The article focuses on the Galápagos as a failure, yet the Galápagos are home to many success stories. At least 27 invasive species populations have already been eradicated. Feral goats
have been eradicated from more than half the archipelago and feral pigs from Santiago Island.
Several nonnative plant species have been eradicated.
CREDI T: (LEF T) S TURGIS MCKEEVER/GEORGIA SOU THERN UNIVERSI TY/ BUGWOOD.ORG; (RIGH T) UNIVERSI T Y OF AUCKLAND/WIKIMEDIA COMMONS
There has also been success elsewhere. More than 1000 eradications have succeeded world-wide, in many cases contributing more than any other conservation action to threatened species
recovery (1). Several red-listed species—including 11 birds, 5 mammals, and 1 amphibian—
have improved their conservation status as a result of eradications of invasives (2). Eradication
campaigns are succeeding in ever-larger areas. Evolution of these technologies has minimized
nontarget impacts and decreased expense.
Moreover, framing the struggle against aggressive invasive species as the unsuccessful
attempt to eradicate completely all nonnatives, as the article does, overlooks the big picture of
conservation. Eradication is but one component of any policy on invasions, which must include
a combination of prevention measures and
early detection, with
(including eradication) of invasive species
serving only as the last
resort (3). For instance,
in the Galápagos, the
cottony cushion scale,
a major threat to both
rare endemic plants
Success story. In the Galápagos, the invasive cottony cushion scale (left) has
been controlled by the introduction of the Australian lady beetle (right).
and to agriculture, though not eliminated, has been well controlled by introduction of an
Australian lady beetle. Plant invasions as massive as any in the Galápagos have long been controlled by biological control (such as the giant salvinia in many regions and prickly pear cactus
in Australia), chemical control (such as the water hyacinth in Florida), physical control (such
as the Eurasian musk thistle in Kentucky), and combinations of the various technologies
(such as European beach grass in California).
New technologies (such as pheromones for sea lamprey and chemical-laden microbeads
for zebra mussels) suggest promising developments for formerly intractable invasions. Many
of these successes and recent developments required years of research; to have declared failure
prematurely would have been a tragic mistake.
Invasion biologists and managers have never argued that success can be defined only as
elimination of every single nonnative; rather, the goal is maintenance of a semblance of the
original community, with all species playing their original roles, and degrees of success can
fall short of this state.
In the face of limited resources, managers are increasingly using weed risk assessment
tools to focus on those introduced plants most likely to become invasive. Furthermore, the
observation that many restoration activities
fail because they facilitate invasive plant seed
germination is a long-recognized problem in
restoration ecology and one that practitioners
are increasingly adept at avoiding.
*To whom correspondence should be addressed. E-mail:
1. D. Simberloff, Biol. Inv. 11, 149 (2009).
2. M. A. McGeoch et al., Diversity Distrib. 16, 95 (2010).
3. J. A. McNeely et al., Eds., A Global Strategy on Invasive
Alien Species (IUCN, Gland, Switzerland, 2001).
New Mosquito Subgroup
IN THEIR REPORT “A CRYPTIC SUBGROUP OF
Anopheles gambiae is highly susceptible
to human malaria parasites” (4 February, p.
596), M. M. Riehle and colleagues discuss
the existence of a previously unknown exophilic subgroup within the major Afrotropical
malaria vector An. gambiae s.s. Their evidence is based on immature mosquitoes that
show a genetic make-up different from that
of the rest of the larval population as well as
from indoor-resting adult females collected
in the same localities in Burkina Faso. We