Geoscience Reference
In-Depth Information
life at the macroscopic scale, microbial processes can sig-
nificantly shape the effects that global climate change has
on terrestrial ecosystems. According to the International
Panel on Climate Change (IPCC) report (2007), warm-
ing of the climate system is occurring at unprecedented
rates and an increase in anthropogenic greenhouse gas
concentrations is responsible for most of this warming.
Soil microorganisms contribute significantly to the pro-
duction and consumption of greenhouse gases, including
carbon dioxide (CO
2
), methane (CH
4
), nitrous oxide (N
2
O)
and nitric oxide (NO), and human activities such as waste
disposal and agriculture have stimulated the production of
greenhouse gases by microbes.
18.1
Introduction
From the primary molecules of oxygen formed by oceanic cya-
nobacteria ~3.5 billion years back to the methanogens luxuri-
ating in the warm, carbon-rich swamps of the Carboniferous
period, microbial processes have long been the key drivers of,
and responders to, climate change Schopf and Packer (1987). It
is widely accepted that microorganisms have played a key part
in determining the atmospheric concentration of greenhouse
gases, including CO
2
, CH
4
and nitrous oxide N
2
O (which have
the greatest impact on radioactive forcing), throughout much
of Earth's history. What is more open to debate is the part that
they will play in the coming decades and centuries, the cli-
mate feedbacks that will be important, and how humankind
might harness microbial processes to manage climate change.
The feedback responses of microorganisms to climate change
in terms of greenhouse gas flux may either amplify (positive
feedback) or reduce (negative feedback) the rate of climate
change. With the twenty-first century projected to experience
some of the most rapid climatic changes in our planet's history,
and with biogenic fluxes of the main anthropogenic green-
house gases being tied integrally to microorganisms, improv-
ing our understanding of microbial processes has never been
so important.
In terrestrial ecosystems, the response of plant communities
and symbiotic microorganisms, such as mycorrhizal fungi and
nitrogen-fixing bacteria, to climate change is well understood;
both in terms of physiology and community structure (Bardgett
et al., 2009). However, the response of the heterotrophic micro-
bial communities in soils to climate change, including warming
