both on land and in the sea, is a key component of the global carbon
cycle. On land, an estimated 60 thousand million tonnes of carbon
is emitted to the atmosphere each year by autotrophic respiration.
A similar amount, about 55 thousand million tonnes, is emitted as
a result of heterotrophic respiration.
In the sea, autotrophic respiration is thought to
account for about 58 thousand million tonnes of the dissolved inorganic
carbon in surface waters each year, with the contribution of heterotrophic
respiration being 34 thousand million tonnes.
Though the worldwide human population has now grown above 6 billion,
our direct contribution to atmospheric carbon dioxide concentrations
via respiration is relatively insignificant. Of more concern is
the impact human-induced global warming could have on global respiration
rates. As temperatures increase rates of respiration also increase
in many organisms, microbes for instance, and there exists a danger
of warming inducing further increases in atmospheric carbon dioxide
concentrations, and so yet more warming.
Potential for control
Quite obviously, limiting global greenhouse gas emissions and,
therefore, future global temperature increases, could help to avoid
the spiral of warming, increased respiration rates, and more warming