Sustainability and policy - Climate Change: Biological and Human Aspects - page 522

trend in increased international transportation, the likelihood is that health risks will
increase.
8.5.3 Futureclimateandhuman-ecologyimplicationsforwildlife
As we have seen, climate and climate change have discernable, indeed marked,
impacts on species and biological systems. Consequently, through a variety of ways
(a number of which were covered in Chapter 2) we have managed to discern many
of the principal global climatic regimes and changes of the past couple of hundred
million years, although, of course, we know far more about relatively recent climate
change than that in distant deep time. The picture that each tool provides is necessarily
incomplete. However, taking evidence together enables the bigger picture to emerge,
and it is still emerging with ongoing research. This picture is coherent as both the
palaeo and current evidence is very much corroborative (Chapters 3 and 4), which in
turn lends confidence to the conclusions drawn.
It is therefore certain that current climate change influences (Chapter 5) and likely
future change (Chapter 6) would, without the presence of humans, cause species
to migrate and ecosystems to transform. Ecotones (the boundary zones between
habitats) will be a focus of profound biological change: one that in no small part
reflects the changes to take place within bordering ecosystems. Yet, in all likelihood,
without humans terrestrial species would largely survive if (as we expect will happen)
a similar amount of carbon were added over the next century to the atmosphere
to that added since the Industrial Revolution (of course, there would be a genetic
fingerprint; Chapter 4). Calcareous marine species, though, would be susceptible
to extinction through increased ocean acidity, as happened with the Initial Eocene
Thermal Maximum (Chapter 3). Other than this, most groups and families of species
would survive and the biosphere would recover. However, this is theoretical. The
reality is that we do currently have a climbing population of over 7 billion humans
that already is exerting considerable pressure on natural systems (Chapter 7), even
without additional impacts due to anthropogenic climate change. So, whereas wildlife
has adapted to the series of considerable glacial-interglacial climatic fluctuations over
the past two million years (Chapter 4), and even major carbon cycle perturbations
earlier still, the past is not the present. First, the current anthropogenic perturbation
of the carbon cycle is far more rapid than previous carbon excursions (consider
the Eocene thermal maximum), as is the commensurate rapidity of global climate
change (even if in the past some regional climate change has been as fast). Second,
competition with humans has seen the landscape fragment: a landscape through which
species adapting to change would have to migrate.
That we do have anthropogenic climate change in addition to an extinction already
taking place (Barnosky et al., 2011) will only serve to enhance threats to species.
Biodiversity is therefore set to continue to decline through the 21st century (Pereira
et al., 2010). That current human pressures include the fragmenting of many natural
terrestrial systems, and management and conversion of others to semi-natural systems,
will impede species' ability to adapt to change. Such negative factors tend to interact
synergistically. For example, a forest subject to climate change is one thing: species
may migrate. Alternatively, a forest that becomes a large island surrounded by highly