cbd-ts-66-en

CHAPTER 7
SYNTHESIS
Part I: Impacts of Climate-related Geoengineering on Biological Diversity
This study has: introduced the range of proposed geoengineering techniques (Chapter 2); reviewed the projected
impacts of likely climate change on biodiversity (Chapter 3); considered the impacts of specific geoengineering
techniques on biodiversity (Chapters 4 and 5); and discussed associated socio-economic and cultural issues (Chapter
6). Based on that information, this chapter provides a short summary of the drivers of biodiversity loss under
the scenarios of (1) continuation of current trends of increasing energy use; (2) rapid and substantive reduction
in greenhouse-gas emissions; and (3) the deployment of geoengineering techniques to address climate change,
against a baseline scenario of (1), i.e. taking little or insufficient action to reduce anthropogenic climate change.
Intermediate and alternative scenarios are also possible.
The chapter also includes remarks on the importance of scale, and highlights key areas where further knowledge
and understanding is required.
7.1 CHANGES IN THE DRIVERS OF BIODIVERSITY LOSS
As noted in Chapter 1, the main direct drivers of biodiversity loss are habitat conversion, over-exploitation, the
introduction of invasive species, pollution and climate change.
For terrestrial ecosystems, the largest driver of biodiversity loss at the global scale has been, and continues to
be, land use change. In the ocean, over-exploitation has been the major cause of ecosystem degradation, with
loss of top predators (fish and marine mammals). For both environments, climate change is rapidly increasing
in importance as a driver of biodiversity loss. However, the relative importance of different drivers of loss vary
between ecosystems, and from region to region.
The baseline scenario (1) described in Chapter 3 considers the climatic consequences of continued anthropogenic
greenhouse-gas emissions, without urgent action to achieve a low-carbon economy at the global scale. Under those
conditions, global temperature increases of 3 to 5°C are projected by 2100, posing an increasingly severe range of threats to
biodiversity and ecosystem services not only as a result of changes in temperature, but also in precipitation, water availability,
sea level and the associated phenomenon of ocean acidification. The impacts are exacerbated by the other anthropogenic
pressures on biodiversity (such as over-exploitation; habitat loss, fragmentation and degradation; the introduction of
non-native species; and pollution) since these reduce the opportunity for gradual ecosystem shifts, population movements
and genetic adaptation. In addition, climate change is likely to increase some of the other drivers; for example, by providing
additional opportunities for invasive alien species (e.g., mixing of Pacific and Atlantic marine plants and animals).
Under this baseline scenario of taking insufficient action to address climate change, the climate change driver will
increase substantially.
Under scenario (2) of addressing climate change through a rapid and substantive reduction in greenhouse-gas
emissions, there would be a transition to a low-carbon economy in both the way we produce and use energy, and
in the way we manage our land. Measures to achieve that effect could include: increased end-use efficiency; the
use of renewable energy technologies alongside nuclear and carbon capture and storage; and ecosystem restoration
and improved land management. These measures would substantially reduce the adverse impacts of climate change
on biodiversity, although significant further climate change is now considered unavoidable. Generally, most other
impacts on biodiversity, mediated through other drivers, would be small (e.g., use of nuclear power to replace
fossil fuels) or positive (e.g., avoided deforestation, ecosystem restoration). Although some of the climate change
mitigation measures have potential negative side-effects on biodiversity (e.g., bird kill by wind farms; disruption of
freshwater ecosystems by hydropower schemes) these can be minimized by careful design. Overall, strong climate
change mitigation measures are expected to be beneficial for biodiversity, and for the provision of ecosystem services.
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