Page 306 - Environment: The Science Behind the Stories

downward both inside and outside
the parks (Figure 2). Many species, 40
including wildebeest, zebras, and 30
some antelope, migrate into and out
of parks, so factors that affect their Thousands of gazelles 20
populations outside the parks will affect
numbers counted within park bounda- 10
ries as well. 0
Researchers have given particular 1975 1980 1985 1990 1995 2000 2005 2010
attention to the Maasai Mara National Year
Reserve, on the Kenyan side of the (a) Inside the reserve
border adjacent to Serengeti National
Park. A decade ago Dutch scientist
Wilber Ottichilo analyzed aerial survey 150
data and concluded that nonmigratory 125
mammals had declined by 58% from
1977 to 1997 within the reserve and by 100
a similar amount outside the reserve. Thousands of gazelles 75
Resident wildebeest had fared even 50
worse, showing an 81% decline. 25
More recently, Joseph Ogutu of 0
the International Livestock Research 1975 1980 1985 1990 1995 2000 2005 2010
Institute in Nairobi, Kenya, and his Year
(b) Outside the reserve
180 Total adjacent Figure 3 Thomson’s gazelles, the most abundant species at Kenya’s Maasai
Population estimate (thousands) 120 colleagues extended the analysis to researchers have concluded that
Mara National reserve, decreased by 59% (a) inside the reserve, and by 77%
160
ecosystems
140
(b) outside the reserve. Data from Ogutu, Joseph, et al., 2011. Continuing wildlife popula-
tion declines and range contraction in the Mara region of Kenya during 1977–2009. Journal of
Zoology 285: 99–109.
100
80
As a result of studies like these,
60
2009 and found that most species had
40
reserve, and were now at just one-third
quate to successfully conserve wildlife
20
and ecosystems. Instead, we need
of their 1977 population sizes (Figure 3).
0 Total parks continued declining, both on and off the merely setting aside parks is not ade-
1980 1990 2000 As in Tanzania and elsewhere in to view the big picture and consider
Year Kenya, drought accounted only for animals’ needs across the landscape,
short-term fluctuations and not long- both inside and outside of reserves,
Figure 2 Wildlife populations have
declined across Kenya, both inside and term declines. The long-term declines as well as how human impacts might
outside parks. Data from Western, D., et al., were due to habitat loss to cropland spill into reserves. Accomplishing CHAPTER 11 • Bi odiv ER si T y A nd Cons ER vAT i on Bi ology
2009. The status of wildlife in protected areas agriculture, intensified human settle- conservation goals thus requires
compared to non-protected areas of Kenya. PLoS ment near the parks, poaching, and working with local people living near
ONE 4(7): e6140. competition with livestock. protected areas.

we continue international trade in exotic pets and ornamental animals have been under siege from invasive organisms such
plants, often heedless of the ecological consequences. as rats, pigs, and cats, and this has led to a number of extinc-
Species native to islands are especially vulnerable to dis- tions (Chapter 3).
ruption from introduced species. Island species have existed Most organisms introduced to new areas perish, but the few
in isolation for millennia with relatively few parasites, types that survive may do very well, especially if they are freed
predators, and competitors; as a result, they have not evolved from the predators and parasites that attacked them back home or
the defenses necessary to resist invaders that are better adapted from the competitors that had limited their access to resources.
to these pressures. For instance, Hawaii’s native plants and Once released from the limiting factors (p. 85) of predation, 305

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