Agriculture Reference
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that could be used to evaluate ecosystem services across national boundaries and as a
basis for quantifying soil quality (Lavelle et al., 2009).
The research initiatives on soil biodiversity and ecosystem functioning and their
resulting benefits to society have developed rapidly and are providing new interdisci-
plinary challenges. However, integrating soil science and soil biodiversity into the larger
issues of biodiversity loss and conservation requires evidence of what we know now and
our collective synthetic expertise for predictions of the future. Questions that need to be
resolved for sustainability of ecosystems and for society are simply as follows: Does it mat-
ter if species or certain trophic groups are lost when soils are heavily perturbed (such as
with intensive agriculture)? If so, does this loss alter ecosystem functioning and the ability
to manage land sustainability to enhance soil ecosystem services? Certain groups, such as
nitrogen-fixing bacteria or larger soil animals, including enchytraeids, earthworms, ter-
mites, or ants, are all known to be vulnerable to disturbance (Wall et al., 2010), and their
loss would significantly affect an ecosystem function and the provision of a service. But
are other groups of soil biota and ecosystem services equally vulnerable? Hunt and Wall
(2002) modeled the loss of soil biodiversity for an arid grassland and showed that ecosys-
tems could sustain loss of some functional groups. For example, only a 10% change in
function was noted with deletion of bacteria, saprophytic fungi, and root-feeding nema-
todes. However, this study did not include effects of climate change drivers.
To address these questions of vulnerability of soil species under multiple global
change drivers, there was a thorough assessment of soil biodiversity and provision of eco-
system services at various management regimes and across spatial and temporal scales
(Wall, 2004). First, van der Putten et al. (2004) assessed the contribution of each group of
soil biotic and abiotic factors (scaled from unimportant to highly important) to the pro-
vision of a range of ecosystem services (or disservices) in several ecosystems, including
tilled agricultural systems. Then, using this synthesis (i.e., van der Putten et al., 2004) and
other reports showing that soil taxonomic groups contributing to an ecosystem service
vary in their response to global change drivers (e.g., land-use change, climate change,
pollution, agricultural intensification, and invasive species) across various spatial scales,
Wardle, Brown, et al. (2004) evaluated the vulnerability of each biotic group to global
change drivers and the consequence for the provision of an ecosystem service. This assess-
ment emphasized not only the impacts of global change drivers on the three ecosystems
studied but also on the linkages above- and belowground. Direct effects of the driver on
organisms on one side of the aboveground-belowground interface will likely stimulate
feedbacks from organisms on the other side of the interface. The analysis showed that
food and fiber production of arable lands was highly vulnerable to global change drivers
such as drought, invasive species, and land-use change because soil biota were altered
and supporting services such as plant production were reduced. This type of assessment
analysis used current knowledge about soil biodiversity and ecosystem functioning to
predict detailed scenarios of the vulnerability of soil biota, ecosystems, and ecosystem
services. Lavelle et al. (2004) explored the scales at which processes that sustain a ser-
vice operate and the scales of the organisms responsible and how they could be used
for managing provision of services (protection, limited use, rotations, etc.). This analysis
expanded from soil to sediment because the scale of disturbances affecting organisms
in one habitat can affect organisms and services farther away and at a larger scale (such
as excess fertilizer in a field affecting nitrogen retention, resulting in runoff and algal
blooms in rivers) (Lavelle et al., 2004).
These and other studies (Wall et al., 2008; Ostle et al., 2009; Woodward et al., 2009)
showed that soil biodiversity, ecosystem processes, and ecosystem services are vulnerable
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