Page 90 - Environment: The Science Behind the Stories

One-quarter of Hakalau is Almost no area remains
above the 13°C isotherm above the 13°C isotherm,
and malaria-free, and so malaria will encompass
nearly all of it is above the the whole refuge.
17°C isotherm.

17°C
isotherm

13°C
isotherm Hakalau
Forest NWR

(a) Today (b) With 2°C of climate warming

Figure 3.21 Researchers have modeled how a warming climate will affect the native birds of
Hakalau Forest NWR. Avian malaria cannot survive where temperatures dip below 13°C, and it peaks where
summer temperatures average 17°C. Today (a), 24% of Hakalau lies above (cooler than) the 13°C isotherm
and is free of malaria. If climate warms by 2°C, however (b), then the isotherms move upslope, and only 1% of
Hakalau will remain cooler than 13°C and malaria-free. Data from: Benning, T.L., et al. 2002. Interactions of climate change
with biological invasions and land use in the Hawaiian Islands: Modeling the fate of endemic birds using a geographic information
systems. Proc Natl. Acad. Sci. 99: 14246–14249.

The challenges of climate change mean that scientists Conclusion
and managers need to come up with new ways to help save
declining populations. We will learn about the many efforts The honeycreepers of Hakalau Forest National Wildlife
being made across the world in our exploration of biodiversity Refuge, along with many other Hawaiian species, have
and conservation biology in Chapter 11. In Hawai‘i, it remains helped to illuminate the fundamentals of evolution and pop-
to be seen how effectively management and ecotourism can ulation ecology that are integral to environmental science.
stem the tide of challenges and help preserve natural systems The evolutionary processes of natural selection, speciation,
in the long term. Resources and efforts to preserve habitat and extinction help determine Earth’s biodiversity. Under-
and protect endangered species will likely need to be stepped standing how ecological processes function at the popula-
up. Programs to restore altered communities to their former tion level is crucial to protecting biodiversity threatened by
condition—as is being done at Hakalau Forest—will also be the mass extinction event that many biologists maintain is
necessary. The restoration of ecological communities is one now underway. Population ecology also informs the study
phenomenon we will examine in our next chapter, as we shift of human populations (Chapter 8), another key endeavor in
from populations to communities. environmental science.

Reviewing objectives CHAPTER 3 • Ev ol u T i on, Bi odiv ER si T y, A nd Po P ul AT i on E C ology

you should now be able to: • We have produced our pets, farm animals, and crop plants
by artificial selection. (p. 70)
Explain natural selection and cite evidence for this
process Describe how evolution influences biodiversity
• Because organisms produce excess young, individuals vary • Natural selection can act as a diversifying force as species
in their traits, and many traits are inherited, some individu- adapt to their environments in myriad ways. (pp. 70–71)
als will prove better at surviving and reproducing. Their • Speciation by geographic isolation (or other means) pro-
genes will be passed on and become more prominent in duces new species. (pp. 71–72)
future generations. (p. 68)
• The branching patterns of phylogenetic trees reflect the
• Mutations and recombination provide the genetic variation historical pattern in which lineages of organisms have
for natural selection. (p. 68) diverged. (p. 72) 89

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