Geology Reference
In-Depth Information
Figure 41: The importance of biodiversity for the health of Gaia (arrows depict influences, not
direct couplings).
Firstly, human influences act directly on biodiversity, or indirectly by changing Gaian
processes such as climate, biogeochemical cycles and other global processes. Human-
induced changes to biodiversity could then affect aspects of ecosystem health, such as
how well an ecosystem resists and recovers from disturbances, how well it recycles
its nutrients and how reliably, and how much biomass it produces over a given period
of time. These various aspects of ecosystem health could feed back to influence biod-
iversity, as changes in nutrient cycling or productivity impact on the species in the eco-
system. Ecosystem health could also have big impacts on Gaian processes, such as the
abundance of greenhouse gases in the atmosphere and the overall albedo of the plan-
et, both of which influence climate. Every species has a preferred climate in which it
feels most comfortable, so Gaian processes feed back to influence biodiversity. Lastly,
altering biodiversity could expose human activities to feedbacks from two directions:
directly from changes to biodiversity, and indirectly if ecosystem health and Gaian pro-
cesses have been affected. Let's look at each of these relationships. Firstly, how are hu-
man activities influencing biodiversity? The answer has been summarised in the famous
acronym 'HIPPO', which tells us that our lethal impacts on biodiversity are, in order of
importance: Habitat destruction and fragmentation, Invasive species, Pollution, Popula-
tion and Over-harvesting.
