Biodiversity Management for Agriculture Outleases for Range and Croplands
Outleasing of areas for agriculture affects biodiversity directly by converting natural
habitats to cultivation, grazing, or other manipulation, and through the associated
repeated disturbances that accompany conversion. Agriculture affects
biodiversity indirectly through water management practices for irrigation and
drainage, soil erosion and sedimentation, and elevated nutrient and pollutant discharges
into the environment.
The restoration of this longleaf pine forest
at Fort Jackson, South Carolina, was accomplished
through the Army's commercial
forestry program. (Photo: U.S. Army)
Agroecosystems (agricultural ecosystems) can be mosaics of pasture, cropland,
woodland, and wetlands, and this patchiness may benefit some species. Agricultural
lands may provide more suitable habitat for native wildlife and birds than
do fragmented and extensively modified urban or suburban lands. When developing
agriculture management plans, it is important that the resources manager
consider the compatibility between biodiversity and agriculture, with key considerations being habitat availability for species at risk, as well as the potential for
economic damage to agriculture caused by wildlife. At the landscape level, agriculture
can best preserve biodiversity when it is incorporated as part of a matrix
of habitats connecting natural areas. In agroecosystems, the conservation of
aquatic biodiversity requires consideration of impacts to aquatic systems from
agricultural nonpoint source pollution and the potential affects on aquatic ecosystem
structure and function from altered hydrology (Blann 2006).
Harvesting wheat from an agricultural outlease
at the Smoky Hill Air National Guard
Range, Kansas. Grazing and cropland leases
at the Smoky Hill Range generate nearly
$400,000 annually, the largest single outleasing
program in the Air Force. (Photo:
Habitat and threats from non-native and invasive species in agricultural lands
directly compete with biodiversity goals. Approximately 46 percent of the plants
and animals federally listed as endangered have been negatively impacted by invasive
species (USDA 2006). The significant threat of invasive species to biodiversity
increasingly is being recognized both internationally and domestically (see
http://invasivespecies.nbii.gov/). Biodiversity goals and objectives outlined in the
inrmp should include contingencies for impacts resulting from invasive and nonnative
species. Early warning of possible negative impacts is possible when biodiversity
management includes monitoring and adaptive management measures.5
Rangeland and pasture management has typically focused on simplifying ecosystem
structure and achieving uniform disturbances across a landscape. Most rangeland
and grazing management techniques were developed under the model of increasing
and sustaining livestock production by decreasing the rangeland diversity.
This approach is obviously incompatible with biodiversity management and prevents
development of an ecological framework for alternative management objectives.
Maintaining biodiversity and preserving habitats for many individual
species is contrary to the typical range management model and depends on the
interspersion of diverse habitat types throughout a heterogeneous rather than a
homogeneous landscape (Fuhlendorf and Engle 2001).
Grazing and Rangeland
At Avon Park AF Range, Florida, aircraft and
cattle share the range. (Photo: Douglas Ripley)
Grazing management includes fencing needs, water development, seeding,
brush control, fertilizing, salt distribution, and intensified animal husbandry (Laycock
1983). Management can be aimed at improving range biodiversity with careful
study of the desired plant species, their phenological characteristics, how they
respond to grazing pressures during each annual season, and annual re-seeding
(Gayaldo 1996). For example, light to moderate grazing of grasslands, oak forests and savanna habitats can potentially promote plant and associated vertebrate
wildlife diversity (EBMUD 2001).
Many of the biological-physical-management interactions associated with
rangeland biodiversity are only beginning to be understood (West 1993). However,
a number of studies have shown that grazing does affect the vegetational
composition of a community (Gayaldo 1996). Long periods of time (several
decades) are required for significant vegetational changes to occur in rangelands,
and are dependent on soil and climatic conditions, competing species, and available
native seed sources. Also, it is documented that more time is required for a
site to progress from a poor to fair condition than from a fair to good condition
(Gayaldo 1996). Livestock grazing and rangeland practices that pertain to water
quality protection are also applicable to habitat protection, and the maintenance
and enhancement of biodiversity. This is particularly true for riparian and aquatic
habitats when livestock access is excluded by establishing buffer zones, and by
providing alternate water supplies for livestock. Prescribed grazing, livestock exclusion,
fencing control and location and timing of livestock impacts are commonly
used to protect and enhance plant and wildlife diversity. Also, establishment
of proper stocking rates and judicious monitoring form the basis for
biodiversity management on outleased watershed lands that are grazed.
Biodiversity guidelines that may be applicable to grazing management at some
military installations include the following (taken from the East Bay Range Resource
Management Plan ):
- Identify high-priority sites for habitat restoration based primarily on water
quality protection and on the value of restored habitats and locations relative to
important wildlife use areas and corridors.
- Monitor listed species populations and conduct site surveys.
- Identify key habitat areas necessary for protection and management of specialstatus
plants and animals. Provide buffer areas to reduce disruption of nesting
and roosting areas for sensitive wildlife species.
- Recognize the ecological value and likely permanence of certain non-native species and habitats (e.g., annual grassland), and incorporate the management of
those species and habitats into biodiversity planning efforts.
- Use prescribed fire, periodic grazing, mastication (chipping trees on site with
either a mulcher head or hydro-axe), or other means to discourage shrub encroachment
and maintain grassland conditions where annual grazing has been eliminated
from grassland habitats and grassland retention is a biodiversity priority.
Hay lease harvest, McEntire Air National
Guard Station, South Carolina. (Photo:
In the United States there have been substantial changes in the mix of cropland
and pastureland over the past century (Blann 2006). The expansion of crop production
over hay and pasture production has been accompanied by more intensive
farming practices, increased farm size, and reductions in shelter belts, field
borders, wetlands, and remnant habitat areas that were previously inconvenient
to farm. Fencerow-to-fencerow farming has reduced biodiversity by eliminating
much nesting, feeding, and winter cover for wildlife (Blann 2006), and croplands
do not provide the stubble fields and harvested grassland habitats important to
many invertebrate, bird and small mammal species.
The influence of agriculture on biodiversity often goes beyond farmed land itself,
as the majority of semi-natural habitats are linked to the surrounding agricultural
land and may be fragmented or isolated within the larger agricultural
landscape. Cropland practices which may impact biodiversity include fertilizer
use; monoculture; abandonment of farmland; removal of field margins such as
hedges, ditches, and fencerows; poor drainage and irrigation, and soil erosion.
It is possible to provide a balanced environment, sustained yields, biologically
mediated soil fertility, and natural pest regulation through the design of diversified
agroecosystems and the use of low-input technologies (Altieri 1995). Different
types of habitats in agricultural landscapes, depending upon their size, shape, and location, may support different types of biodiversity. Non-farmed areas can be
used to provide patches of certain habitat types, or to form corridors linking protected
areas and enabling species to maintain genetic contact between otherwise
isolated populations. Such benefits can be achieved on outleases via lease agreement
language and through programs such as the ACUB process. Agricultural areas
can make a positive contribution to diversity when the surrounding matrix is
managed with biodiversity in mind.
Fishing on many military bases (USAF Academy,
top, and Edwards AFB, below) is an
important recreational activity for military
personnel and civilians. Fishing and hunting
permits sold under the authority of the
Sikes Act are a valuable source of revenuefor
military natural resources programs.
(Photos: Douglas Ripley)
Blann (2006) offers the following cropland practices for biodiversity management
(adapted from Granatstein  and Bird et al. ). These practices
could readily be implemented on outleased lands through the lease agreements
and enforcement procedures.
- Practice soil conservation measures. Increase protective cover on the soil surface,
using no-till, cover crops, windbreaks, contour strip cropping, and grass
- Eliminate or minimize intensive row-cropping and tillage on highly erodible
land, and on sensitive lands such as floodplains, riparian areas, wetlands, and
- Use a greater variety of crops grown in more complex rotations. This breaks
weed and disease cycles.
- Enhance habitat quality to encourage and enhance wildlife diversity. Use cover
crops and soil-building crops like legumes, such as clover and alfalfa, and grass.
Integrate crops and livestock production with intensively managed grazing and
recycling of manure to build soils.
- Use integrated pest management, in which pest levels are monitored, biological
controls are used wherever available, and chemicals used only when an economic
threshold is reached.
- Nutrient inputs should be managed to maximize efficiency and minimize nutrient
movement to surface water and groundwater.
- Properly store and apply animal manures. Compost manures and other wastes.
- In arid regions and other areas relying heavily on irrigation, develop and implement
management systems for efficient water use. Water-intensive crops that
compete with instream uses often impose high costs on local ecosystems. Cropping
systems should be matched to local and regional climatic and environmental
Proceed to Next Section: Biodiversity Management for Hunting, Fishind and Recreational Uses