Agriculture Reference
In-Depth Information
agriculture, and increasingly, society is recognizing the potential for other
services such as improved water quality, the protection and enhancement of
biodiversity, climate stabilization via carbon sequestration and greenhouse gas
abatement, and social amenities such as verdant landscapes and agrotourism
(Robertson and Swinton 2005, Power 2010, Swinton et al. 2015a, Chapter 3 in
this volume). Agriculture also produces disservices (Swinton et al. 2007): unde-
sirable effects such as erosion, nitrate pollution (e.g., Syswerda et al. 2012), and
emissions of greenhouse gases such as nitrous oxide (Gelfand and Robertson
2015, Chapter 12 in this volume). Mitigation services provided by alternative
practices or other parts of the agricultural landscape can also be considered ser-
vices provided by agriculture (Swinton et al. 2007). We refer in general to the
implementation of agricultural practices that improve the delivery of ecosystem
services as “farming for services” (Robertson et al. 2014).
Agriculture is typically subject to a complex set of drivers, including shifts
in climate, commodity markets, human population and land use, and social and
regulatory environments, as well as subject to new developments in agricultural
technology such as genetically improved crop varieties and new tillage practices.
Drivers of change that affect both human and natural systems occur on scales from
local to landscape to global and operate under variable time scales. Conceptually,
we view these drivers as disturbances to the biophysical or social systems (Fig. 1.4).
They can be broadly classified into either “pulse” or “press” disturbances, depend-
ing on whether they occur as discrete events or as gradual changes over a more
protracted period, respectively (Collins et al. 2011). They can be further grouped
into those that are intentional management decisions vs. those that are unintentional
and often unanticipated.
Intentional pulsed disturbances that affect field crops include tillage, planting,
harvest, and fertilizer and pesticide applications; intentional presses include the
gradual adoption of newly developed crop varieties and management technologies.
Unintentional pulses include episodic weather events such as short-term droughts
and late frosts as well as pest and disease outbreaks, whereas unintentional presses
include climate change, increasing atmospheric carbon dioxide (CO
2
) concen-
trations, and declining soil carbon stores. Pulses and presses may act alone or
synergistically to affect how we farm, where we farm, and the profitability and
sustainability of farming (Gage et al. 2015, Chapter 4 in this volume) as well as the
short- and long-term impacts of agricultural activities on the environment at scales
from local to global.
Most KBS LTER research to date has emphasized developing an ecosystem-level
understanding of ecological structure and function—the right-hand portion of the
model (Fig. 1.4). Biotic structure includes organisms and their adaptations, popula-
tion and community assemblages, and the physical organization of different ecosys-
tem habitats. Ecosystem function includes the processes carried out by organisms as
mediated by the abiotic environment—for example, the cycling of carbon, nitrogen,
and other nutrients, energy capture and flow, and hydrologic dynamics. Linkages
between ecological structure and function largely define the mechanisms that sup-
port the delivery of ecosystem services.
