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Into the Wild: Vegetation, Alien Plants, and Familiar Fire at the Exurban Frontier


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The spatial expansion of human populations threatens or alters ecosystems on much of the country’s privately owned exurbaland. These impacts affect the many ways that plants, animals, and environments interact and influence one another. This chapter considers exurban impacts to plant habitat, plant species, plant community structure, ecological processes, and social conditions within, nearby, and at a distance from development. The properties of major vegetation eco-regions in the United States are described and how and why exurban development alters ecological processes over varying spatial and temporal scales is explained. Issues such as fire suppression, land fragmentation, and the introduction of nonnative vegetation are discussed as artifacts of exurban land development. The chapter also draws on the research literature to discuss why specific development densities and configurations are best suited for particular vegetation regimes and points to the mitigation techniques that have proven most successful.
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Chapter 8
Into the Wild: Vegetation, Alien Plants,
and Familiar Fire at the Exurban Frontier
Lynn Huntsinger
Abstract The spatial expansion of human populations threatens or alters ecosys-
tems on much of the country’s privately owned exurban land. These impacts affect
the many ways that plants, animals, and environments interact and influence one
another. This chapter considers exurban impacts to plant habitat, plant species, plant
community structure, ecological processes, and social conditions within, nearby,
and at a distance from development. The properties of major vegetation eco-regions
in the United States are described and how and why exurban development alters eco-
logical processes over varying spatial and temporal scales is explained. Issues such
as fire suppression, land fragmentation, and the introduction of nonnative vegetation
are discussed as artifacts of exurban land development. The chapter also draws on
the research literature to discuss why specific development densities and configura-
tions are best suited for particular vegetation regimes and points to the mitigation
techniques that have proven most successful.
As primary producers of ecosystems, plants capture solar energy that sustains life,
while also serving as the foundation of ecosystem biodiversity. Vegetation provides
habitat and food for wildlife, protects and feeds the soil, and stores and cycles water
and other nutrients. Exurban development changes vegetation within and adjoining
it, but also can change conditions far from the development site. Direct displacement
and alteration of vegetation and indirect effects on ecological processes and species
composition are characteristic impacts. Long-term effects may be cumulative and
affect entire landscapes and distant areas. Fire and introduced species associated
with exurban development are extraordinarily costly and far-reaching. This chapter
L. Huntsinger (B)
Department of Environmental Science, Policy, and Management, University of California,
Berkeley, Berkeley, CA 94720, USA
A.X. Esparza, G. McPherson (eds.), The Planner’s Guide to Natural Resource
!Springer Science+Business Media, LLC 2009
134 L. Huntsinger
explores what is known about the effects of exurban development on vegetation.
The specific impacts of exurban development vary with the ecosystem and the char-
acteristics of the development, so while this chapter presents general concepts, it
cannot capture every situation. Instead the focus is on concepts of broad applicabil-
ity to generic forest, rangeland, and desert ecosystems. These concepts have much
in common with development impacts on wildlife but, unlike animals, plants cannot
move from one spot to another except through reproduction and growth.
Before discussing the influence of exurban change, it is important to consider
what kinds of land uses might precede exurban development. Presumably exur-
ban expansion occurs on privately owned land that is rural in character (Fig. 8.1).
While some of this land may truly be “vacant,” it is more likely used by the
owner for farming, grazing, forestry, hunting, and/or recreation. Vegetation often
has already been exposed to management for various goods and services and has
changed and adjusted as a result. For example, plant communities may have devel-
oped based on irrigation ponds and canals, and a spectrum of exotic species may
have been introduced intentionally or inadvertently. Trees and shrubs may have
been cleared for grazing, forests thinned or genetically improved for timber pro-
duction, game brought in for hunting, and fields created and plowed for farming.
Exurban development ends these uses and introduces new factors that shape plant
Fig. 8.1 The term “ranch”
takes on new meaning in an
exurban environment.
Photograph by Lynn
For decades, maintaining biological diversity through protection of particular
species and habitats has been a primary focus of conservation. Ecologists now real-
ize the need to maintain the integrity of an ecosystem, rather than only elements of it.
“Ecological integrity” means that ecosystems are self-sustaining over long periods
of time. Thus, conserving the ecological integrity of an ecosystem means maintain-
ing not only biodiversity but also the processes that create structural and biological
diversity and enable the persistence of plant communities. These processes include
the many ways plants, animals, and environments interact and influence one another.
8 Into the Wild: Vegetation, Alien Plants, and Familiar Fire 135
This chapter considers exurban impacts to plant habitat, plant species, plant com-
munity structure, ecological processes, and social conditions within, nearby, and at
Plant Habitat
Plant habitats are places where populations of plants normally are found. Habitats
are determined by the soils, climate, water dynamics, and topography of an area,
contemporary as well as historical influences, and the interactions among species at
statured plants that need abundant sunlight. Creation of a pond or watercourse
creates habitat for plants that need consistent access to water, often referred to as
riparian vegetation (see Chapter 10 for a discussion of riparian habitats). A history
of plowing for crop production changes the kinds of seeds and soils found on a site
and may influence vegetation long into the future, creating habitat for plants that
grow well in previously plowed areas. The suburban landowner, by regularly mow-
ing the lawn and adding fertilizer, hopes to create habitat for lawn grasses—though
the wily dandelion has found a way to occupy the same habitat.
Plant communities are groups of plants that share a habitat. The concept of com-
munity can be applied across a wide range of scales, from the plant community
along the shores of a small pond to the Amazon rain forest. The species in a plant
community interact with each other and with the environment and exist in recog-
nizable forms that develop repeatedly over space and time, such as oak woodlands,
pine forests, desert grassland, or sagebrush grassland. Plant communities are named
for the characteristic plant species within them or for characteristic environmental
The location of exurban development often is correlated with high levels of biodi-
versity because both are influenced by biophysical factors, particularly the presence
of water. Unusual rock outcrops or landscapes with abundant visual complexity,
which attract development, often harbor unusual habitats (Fig. 8.2). The ecological
importance of a habitat can be much greater than is suggested by its size (Naiman
and Décamps 1997). Consequently, the effects on biodiversity may be dispropor-
tionately large relative to the size of the exurban development (Hansen et al. 2005).
Rare habitats include those on unusual or endemic soils, where only long-adapted
natives can grow. The few small wetlands in a desert area, or the meadows in an
otherwise heavily forested landscape, are relatively rare habitats that also are desir-
able places for humans to live.
that are genetically different from those growing elsewhere. These habitats may
contribute significantly to the compositional and structural complexity of a region
(Dale et al. 2005). An example of a relatively rare habitat is the vernal-pool habitat
that develops temporarily in spring on soils with a hardpan that slows or prevents
water drainage. The unique chemistry of the water, the harsh and variable growing
136 L. Huntsinger
Fig. 8.2 Although this
vacant ranch is now within
a preserve, the setting
illustrates the convergence
of attractive scenery and
riparian vegetation that leads
to high interest in exurban
development but also
relatively high levels
of biodiversity. Photograph
by Lynn Huntsinger
conditions, and the geographic isolation of individual pools lead to the development
of unique, very localized, species (Solomeshch, Barbour and Holland 2007). Exur-
ban development changes plant habitats profoundly (Table 8.1). Rural land uses
such as forestry or livestock grazing are heavily constrained by the environmental
conditions native to a site. Exurban development can bring far more resources to
bear on changing habitat, using intensive fertilization, pest and weed control, water
application, seeding, planting, and manipulation of existing plants. Because of this
manipulation, and the displacement of habitat by paving, construction, and associ-
ated disturbance, habitats often are completely eliminated and replaced with others
within a development. Nearby habitats are influenced directly by road construction,
changes in management, and the introduction of new species that are able to natu-
ralize and spread into the undeveloped land (Table 8.1). Further, additions of water
and nutrients may exceed levels that can be used by plants in the local climate, and
the excess may create polluted runoff that affects other habitats. Additions of water
and fertilizer typically alter and often reduce biodiversity (Dale et al. 2005).
Plant Species
Species and networks of interacting species have broad, ecosystem-level impacts
(Dale et al. 2005). One species may play a more obviously crucial role in an ecosys-
tem than others, as when it occupies a large area, or provides habitat for pollinators,
or is a crucial link in a complex food web (Dale et al. 2005). One species may mod-
ify habitat so that another can use it, by building soil or fixing nitrogen. Endemic
or rare species are restricted to very small areas, yet they provide functions that are
critical to other species. The ultimate impacts of species change to biodiversity are
difficult to predict and may have unexpected results because of the complexity of
plant interactions with each other and with the environment (Power et al. 1996).
Sometimes the processes associated with a single species can turn out to be critical
8 Into the Wild: Vegetation, Alien Plants, and Familiar Fire 137
Tabl e 8.1 Impacts of exurban development on vegetation
With in the development Sur rounding area Dis tant but li nked areas
Structure Vegetation structure altered
directly by pruning, removal,
additions, clearing of defensible
space, construction, and paving
Fragmentation of previously continuous habitat
into spatially separated and smaller patches.
Additional edge and more patchy environment,
loss or creation of corridors for species
migration, less core habitat. Pollination may be
influenced by changes in patchiness or
connectivity and introduction of new species.
Roads and trails become vectors for the spread
of invasive plants, plant pests, and diseases
Reservoirs to hold water, levees and
channelization, and draining of
wetlands may all be caused by the
need to supply water to exurban
developments and to protect them
from flooding. Road, pipelines and
power lines fragment habitat
Suppression of most ecological
processes, including disturbance
regimes, nutrient cycling,
species interactions
Ecosystem processes, feedbacks between
environment and plants, interactions between
plants, nutrient cycling, disturbance regimes
may be changed or suppressed by management
or the introduction of new species
Vegetation adapted to water-based
disturbance regimes or access to wet
soils and riparian areas will be
altered. Air quality change may
affect plant communities
Massive displacement of wild with
domesticated plants, new species
are introduced, and others are
controlled or reduced. Plant
pests and diseases, and
herbivores, may be introduced or
Spread of invasive species, plant pests and
diseases, and new herbivores. Plants that can
live under natural conditions may naturalize in
the surrounding areas, changing the character
of plant communities and altering ecological
processes. New diseases and herbivores, or
herbivore predators, may also affect the
surrounding vegetation. These changes are
continuous and do not have a foreseeable end
The spread of invasive species, plant
pests and diseases, and new
herbivores may extend over huge
138 L. Huntsinger
Table 8.1 (continued)
With in the development Sur rounding area Dis tant but li nked areas
Significantly altered because of
large inputs of chemicals, water,
and materials. Changes in water
availability, soils, wind and
thermal patterns, erosion, fire,
flooding, localized pollution. May
lose small habitats entirely, new
ones created. May extend and
increase supply of green growth
or biomass through year
Risks to nearby homes makes prescribed burning,
use of herbicides, tree thinning, more costly
and sometimes impossible. Changes in water
use and availability as streams are allocated,
diverted, or controlled. Tree thinning, fuel
breaks, vegetation manipulation may extend to
nearby areas and influence habitats.
Suppression of disturbance regimes changes
Roadside habitats created, riparian
habitats altered
and economic
Landowner goals for residential
living are dominant and may
require complete change in
vegetation; management for
defensible space; pets. New
residents may not recognize or
comply with social norms of
behavior. Absentee ownerships
may make community
management strategies less
New constituencies favoring one type or another
of management and protection for surrounding
lands. Loss of community, infrastructure,
political voice, and conflicts with new residents
makes forestry, ranching, farming, and hunting
more difficult and more regulated. This leads to
habitat and vegetation change. New groups
seek to influence traditional uses and
management of public and private lands. Local
economy may come to depend on commuter
and/or retiree economy. Loss of infrastructure
and community may accelerate conversion to
exurban use
Change in the relative influence of
different groups on local and
eventually more distant planning and
political processes. Need for services
may extend impacts
8 Into the Wild: Vegetation, Alien Plants, and Familiar Fire 139
to ecosystem functions (Dale et al. 2005). Exurban development creates widespread
change by introducing new species or changing habitat, adding barriers to move-
ment or dispersal, introducing new herbivores, and changing competitive dynamics
among species (Table 8.1).
Ecosystems vary in the number and density of plants and plant species they con-
tain. The absolute number of species or density of plants is not necessarily an indica-
tor of the status of an ecosystem or plant community. Redwood forests in California,
for example, have comparatively few species, despite being a relatively intact native
plant community. The density of plants may be very low in desert areas, reflecting
limited soil and water resources. However, one general statement is that the native
species present on a site have adapted to the site and to each other over evolutionary
time, creating a persistent plant community. In turn, the wildlife species, soil condi-
tions, water, nutrient cycling, and other ecological processes linked to this particu-
lar complex of plants will change if the plant community changes. For this reason,
the proportion of native species on a site is sometimes considered an indicator of
ecosystem health.
Exurban developments favor species that are adapted to human-altered environ-
ments. Nonnative and weedy species generally increase (Hansen et al. 2005). New
residents bring in exotic species for landscaping or gardening and control native
species that are not desirable to the owner. Humans act as unwitting vectors for inva-
sive plants whose seeds are carried on clothing or pet fur. Introduction of nonnative
species can have profound affects on plant communities, because the relationships
among plants and environment that has evolved over time can be severely altered, in
turn changing species composition and ultimately, wildlife habitats and site charac-
teristics. For example, a new species that uses water more rapidly than native desert
species can prevent natives from obtaining the water they need. Highly aggressive
plants out-compete the natives, shading them or excluding them from their habitat.
Nonnative plants may assume a focal role in an ecosystem and change community
composition and ecosystem processes in their roles as competitors or vectors for
pathogens and disease and through effects on water balance, soils, productivity, and
habitat structure (Drake et al. 1989).
In some areas, rural land uses have already changed plant communities signif-
icantly. Yet these communities may have achieved relative stability over time by
adjusting to or persisting despite rural land uses over the last 200 or so years. Exur-
ban development will inevitably introduce new species into these and other nearby
plant communities, causing new kinds of change. The extent and impact of this
change is unknown. Increased fire frequency and air pollution during the last sev-
eral decades in southern California facilitated the widespread conversion of coastal
sage shrubland to exotic grassland systems (Talluto and Suding 2008). Effects on
biodiversity are cumulative and often nonlinear and continue to emerge for decades
after development occurs (Maestas, Knight and Gilgert 2003; Hansen et al. 2005).
In addition to introduction of new species, exurban development fosters vegeta-
tion change by altering water availability. The new and/or better-watered plants have
characteristics that attract some wildlife species and increase their numbers. Plants
may remain green when native species are dry during the summer or in drought,
140 L. Huntsinger
or produce fruits and leaves that are particularly tasty and nutritious. One com-
mon animal that can prosper from exurban practices is the deer. In much of the
United States, local deer species adapt well to exurban food sources and battles
ensue as landowners struggle to protect their landscaping from the rapacious her-
bivores. Pocket gophers enjoy the softer, irrigated soils of irrigated landscaping.
Each plant species responds differently to changes in habitat, and regardless of the
type of change, some species will benefit and others will decline. Three levels of
development in coastal California did not alter overall numbers and diversity of
woodland birds, but the species present did change (Merenlender, Heise and Brooks
1998). Specifically, more nonnative species were associated with the more inten-
sively developed areas. A survey of rangelands conducted in Colorado found that
private ranchlands had plant communities with higher native species richness and
lower nonnative species richness and cover than did exurban areas or protected areas
(Maestas, Knight and Gilgert 2003).
Plant communities have structure that creates habitat and affects species composi-
tion. Vertical layers of vegetation, canopy, shrub, and herb layers – comprise vertical
structure. Across a landscape – varying proportions of rock outcrops, shrubs, trees,
grasses, and watercourses create a horizontal landscape mosaic of habitat patches of
varying sizes, termed horizontal structure (Giusti, McCreary and Standiford 2005).
In grasslands, vegetation is short and flexible. Shrubs introduce a woody component,
adding height and complexity. Trees add further height, large trunks, and extensive
canopies. Each increase in vertical complexity adds additional habitats for plants as
well as wildlife in the landscape. Trees and shrubs provide shady habitats for plants,
for example, or arboreal habitat for mosses and lichens.
Horizontally, a continuous forest provides one kind of vegetation structure with
relatively few low-growing species and extensive, contiguous canopy. A patchy for-
est provides a mix of treed and open areas where grasses and shrubs can grow. The
roads, clearings, houses, and pipelines associated with exurban development inter-
rupt horizontal structure and create new habitats, fragmenting contiguous areas into
smaller patches (Table 8.1). This results in greater amounts of “edge” habitat and
smaller amounts of “core” or interior habitat, benefiting edge species while reducing
core plant and animal species. The edges and cores of plant communities can have
quite different conditions and habitats, and the abundance of edge and interior habi-
tat varies with patch size. Fragmentation of plant communities may enhance suscep-
tibility to a variety of disturbances, including windthrow, pest epidemics, invasion
by nonnative species (Franklin and Forman 1987), and increased grazing pressure
from native or nonnative herbivores.
Housing and pavement obviously eliminate vegetation structure, and plantings
create new structure. A road creates patches where sunlight can reach plants, but
reduces the connectedness and extent of contiguous canopy in a forest, thereby
8 Into the Wild: Vegetation, Alien Plants, and Familiar Fire 141
fragmenting the habitat. Roads fragment deserts and rangelands and act as vectors
for nonnative species (Gelbard and Belnap 2003). Corridors, or linkages among
plant communities that are often recommended for wildlife, also provide opportu-
nities for the spread of invasive plant species (see Chapter 5 for a discussion of
fragmentation, corridors, patches, and edges). Fuel breaks constructed to protect
developments facilitate the spread of nonnative species. A statewide study in Cali-
fornia found that nonnative plant abundance was over 200% higher on fuel breaks
than in adjacent wildland areas. There was a significant decline in relative non-
native cover with increasing distance from the fuel break (Merriam, Keeley and
Beyers 2006).
Exurban development can have other direct impacts on vegetation structure. In
addition to the complete replacement of native communities with residential land-
scaping, remnant native vegetation may be thinned, cleared, or pruned, sometimes
for fire prevention. Particular plants may be encouraged to grow with watering or
protection from herbivores and fire. Indirectly, impacts to surrounding vegetation
structure can be strong. For example, the need to suppress wildfires near develop-
ments may change vegetation with the infilling of trees and shrubs into more open
woodlands or grasslands. Unfortunately, together with the increased likelihood of
fire with increased human activity, over time this will in turn increase fire hazard to
the community.
Ecological Processes
Ecosystem processes are critical to the persistence of plant communities and are
affected directly and indirectly by exurban development (Table 8.1). Ecosystems
are shaped by processes such as herbivory, competition, interrelationships of plants
and environment, pollination, and nutrient cycling. Exurban development alters bio-
geochemical cycles that can change the pace or direction of ecosystem change for
decades or centuries (Dale et al. 2005) (Table 8.1). For example, deposition of nitro-
gen from auto exhaust favors nonnative grasses in northern California, eliminat-
ing the habitat of the rare, endemic Bay checkerspot butterfly (Euphydryas editha
ent cycling (Vitousek 1986; Lyons and Schwartz 2001). An overall loss of nitro-
gen in an ecosystem resulting from the takeover of a sagebrush site by nonnative
cheatgrass (Bromus tectorum)hasbeendocumented(Evansetal.2001).Clearingof
vegetation releases carbon and nitrogen, and changes soil moisture regimes.
Species interactions can change or stabilize plant communities. For example, in
some environments competition between plants leads to the development of plant
communities dominated by the tallest species or suite of species capable of occupy-
ing a particular habitat. These communities, sometimes termed “climax communi-
ties,” can be quite stable in the absence of disturbance. On the other hand, in arid
environments a lack of soil nutrients or water overwhelms the effects of compe-
tition among plants, and the community that develops is determined more by the
142 L. Huntsinger
ability of a particular species or a suite of species to use the available habitats.
Internal regulating forces and relationships, such as competition and nutrient avail-
ability and cycling, maintain a plant community within certain bounds (Perry, Oren
and Hart 2008). To cross those bounds and become a different plant community is
often represented as crossing a threshold of some sort, where return to the origi-
nal plant community is unlikely to happen without external intervention. The plant
community settles into a configuration within a new set of boundaries, sometimes
represented as similar to the way a ball rests in a cup.
Vario u s d i s t u r b a n c e s c a n d i s r u p t t h e e c o s y s t e m s internal regulating processes,
including competition and nutrient cycling (Dale et al. 2005). Disturbance is often
it. Fire is perhaps the most classic example, but flooding, severe drought, wind-
storms, plowing, clearing, and even cessation of herbivory are disturbances. Some
plant communities depend on native disturbance regimes—particular patterns and
frequencies of disturbance––to maintain stability. For example, in some shrub com-
munities, there are many ecological processes and adaptations that enable swift
recovery from a common disturbance such as wildfire. After the fire a suite of spe-
cially adapted fire-following species occupies the site, some of which require fire to
germinate or to create suitable habitat. Shrubs are quickly able to reseed or resprout
and reoccupy the site within a few years. The shrub plant community is resilient to
fire, in that wildfire does not move it beyond the bounds that define it. The plant
community may look different after burning and take a while to recover its former
appearance, but it does not change to a different plant community for any significant
length of time.
Ecological feedback processes create resilience and persistence despite distur-
bance. Resilience is the capacity of an ecosystem or plant community to recover
structure and function after disturbance (Walker and Fortmann 2003). In a forest
community that experiences frequent fire, the understory has little to burn, limiting
the possibility of fire getting into the canopy layer and killing the trees. The forest is
quite resistant to fire, or resilient, because of this feedback cycle, where fire begets
less severe fire. On the other hand, changes in the frequency and type of fires or other
disturbances can destabilize plant communities (Keeley, Lubin and Fotheringham
2003), because the ecological processes that enable persistence may only function
within the native fire regime. For example, a forest may recover very quickly from
fire frequency, trees become more tightly packed and smaller trees carry the next
fire into the canopy, resulting in high tree mortality. Exurban development generally
entails fire suppression, disrupting fire feedback processes and leading to a loss of
resilience to fire.
Land-use changes that alter natural disturbance regimes or initiate new distur-
bances are likely to cause changes in species abundance and distribution, species
composition, and ecosystem function (Yarie et al. 1998). Flood control or water
appropriation for exurban development may disrupt ecological processes in plant
communities that are adapted to frequent flooding or particular patterns of water
availability, changing habitat characteristics, species composition, nutrient cycling
8 Into the Wild: Vegetation, Alien Plants, and Familiar Fire 143
and habitat characteristics, among other things. Fires that are too frequent may pre-
vent the woody component of a shrub-dominated community from coming back,
and create habitat for invasive species.
The introduction of a new species can affect resilience by derailing native
response processes. Even if a disturbance regime is not changed, the presence of
invasive plant is able to take over the site after a fire, the native species that would
otherwise come in may be unable to establish. This can cause permanent change
to the plant community. In Sierran forests, Keeley (2006) found that because of the
presence of new species, wildfire, and even prescribed low intensity fire to which
Sierra forests once would have been quite resilient, now serves to spread invasive
species and further change ecosystems. A critical problem for ecologists today is
that ecosystems have changed, and the processes that maintained stability in the
past may not work in present and future conditions.
As opposed to feedbacks that maintain stability within bounds, cycles may be
initiated that, if not dampened or mitigated, can lead to costly and self-perpetuating
changes in vegetation at the landscape scale. A relentless positive feedback can
lead to great change, as with the introduction of cheatgrass (Bromus tectorum)to
intermountain sagebrush rangelands (Menakis, Osborne and Miller 2003). Cheat-
grass successfully makes use of available habitat opened up by land clearing, over-
grazing, wildfire, and other disturbances to the existing vegetation, maintaining site
occupancy by quickly using up available water resources early in the spring. The
annual growth habit of the species results in an abundant dry biomass over the sum-
mer that leads to frequent fire, much more frequent than is believed to occur under
natural fire regimes, thereby reducing the native shrubby component and opening
up more areas to cheatgrass, which in turn leads to more fire. Ultimately, the vege-
tation changes to a cheatgrass-dominated grassland. This grassland may continue to
expand into other plant communities by fostering fires that open up more habitats
for cheatgrass, affecting the distribution and character of plant communities at the
landscape scale.
Changes in ecological processes may be slow to reveal themselves. The effects
of increased fire hazard resulting from the introduction of new species, or infilling
of native species due to fire suppression, or the cessation of forestry and agricul-
ture in areas surrounding development may not manifest for decades. The impacts
of new pests on desert species, or a lack of reproduction in slow growing and slow
changing desert environments, may take a long time to detect. Yet these changes
can have far-reaching and persistent effects. The loss of pollinators due to decline in
habitats that support the reproduction of native bees and wasps may not ever be rec-
ognized. Instead, the disappearances of the plants that depend on them are attributed
to something else. Impacts may also take a long time to develop. The cumulative
effects of development may lead to gradual change, as when increased nitrogen
from automobile exhaust alters the composition of plant communities over time.
Exurban development can be seen as a form of disturbance, but it is not a
form to which existing plant communities are adapted. Millennia of exposure to
certain kinds of disturbance, including drought, flooding, and fire, has resulted in
144 L. Huntsinger
some western plant communities being quite resilient to certain frequencies and
types of each, with feedback processes that maintain stability. There has been no
such opportunity for the evolution of stability-maintaining feedbacks with exurban
development, including the introduction of new species and changes in site char-
acteristics that accompany it. The impacts take us into uncharted territory, and our
ability to anticipate long-term outcomes is limited.
Social and Economic Impacts
Private rural lands are an important buffer between public lands and urban devel-
opment, but exurban development on the edges of public lands disrupts that buffer
(Talbert, Knight and Mitchell 2007). Exurban development affects many social and
economic conditions, which in turn alter vegetation (Table 8.1). Public lands add
value to development, but this means that for the foreseeable future the new devel-
opment will influence, and be influenced by, the management of public lands. Once
houses are introduced into the mix, vegetation management priorities and options
are changed, essentially forever. Ecological processes such as fire can no longer
be allowed to occur, and invasive plants, pets, human fire starts, and other exur-
ban impacts will more directly affect nearby public lands. Prescribed burning and
grazing are often lost as management options (Fried and Huntsinger 1998).
impacts on plants, but the loss of farm, ranch, and forestry enterprises can also
establish a feedback cycle that can lead to even greater loss of rural land and fos-
ter more exurban development. Exurban expansion into farms, forest, or rangeland
fragments rural lands and results in development surrounded by privately owned
production land. Suburban neighbors may object to timber harvest, animal manage-
ment, and crop management practices, and conflicts and vandalism increase costs
to rural enterprises. Exurban residents may be unaware of or unwilling to follow
the social norms of behavior and interaction that have been a part of rural commu-
nities for decades (Ellickson 1991; Yung and Belsky 2007). Producers draw on a
community of other producers for support, shared labor, and information. As rural
enterprises disappear, this community grows smaller and farmers, ranchers, and for-
est owners become more isolated.
Further, ranches and farms require access to infrastructure, including veteri-
narians, packing houses, processing facilities, and agricultural advisory services
(Huntsinger and Hopkinson 1996). Forestry enterprises require equipment and
mills, as well as skilled labor. As lands are developed, there are fewer rural enter-
prises to support this infrastructure. With each forest, farm, or ranch that ceases to
exist, the remaining enterprises become more vulnerable to conversion (Liffmann,
Huntsinger and Forero 2000) (Fig. 8.3). This feedback cycle can eventually lead to
the loss of rural enterprises over a wide area. In one study of exurbanizing commu-
nities, ranchers had seen an average of 10 neighboring ranches sold for development
and stated that this was an important reason they might sell their ranch (Sulak and
Huntsinger 2002).
8 Into the Wild: Vegetation, Alien Plants, and Familiar Fire 145
Fig. 8.3 Development
feedback loop. As rural
enterprises are converted
to exurban development,
pressure to sell on the
remaining enterprises
increases. Source: Lynn
For historical reasons, privately owned rural lands generally have more water and
better soils than publically owned land. In addition, private rural lands offer habitats
unavailable on public or urban lands. For example, privately owned wetlands pro-
vide migratory waterfowl in conjunction with rice production in the central valley
of California. In the Sierra Nevada, where public and private lands are interwoven,
public forests have been profoundly changed by fire suppression, while ranchers his-
torically have maintained relatively fire-resilient open woodlands through grazing,
brush control, prescribed burning, and tree thinning (Sulak and Huntsinger 2002).
Another form of “exurban expansion” is the purchase of production-oriented
properties for urban refugees who then manage the properties for amenity values:
ership emphasis leads to a shift in ecosystems. In southwestern Montana, Gosnell,
Haggerty and Byorth (2007) found that new owners managed water differently than
long-time owners, influencing the region’s fisheries in positive and negative ways.
In the Rocky Mountain region, Gosnell and Travis (2005) found that about half of
the ranches sold were going to amenity buyers, who often had quite different views
about land and vegetation use and management than the rural populace. In some
high-amenity developments, properties are often vacation or second homes. Absen-
tee owners are less likely to take part in the community and in collaborative efforts
at vegetation management and fire-hazard reduction and may be difficult to contact.
Amenity buyers add a new political dimension to local communities and a different
set of goals for land management.
Exurban residents may quickly outnumber rural residents and change the eco-
nomics and politics of a region (Gosnell and Travis 2005; Sheridan 2007). While
the rural community may value its historical connection with and shaping of the
landscape, new residents may be attracted to exurban development because of a
perceived lack of people and human impacts in an area. Exurban and rural resi-
dents may have very different expectations of the “country life” and how vegetation
should be managed (Masuda and Garvin 2008). In-migrants may bring with them
particular “aesthetic” or “consumption” views of a landscape that long-time res-
idents view as political threats. In one example these tensions ignited a political
firestorm over a proposal by the environmentalist-dominated county government
to incorporate landscape-scale aesthetic and environmental principles into county
planning (Walker and Fortmann 2003) (see Chapter 13 for further discussion of
rural attitudes toward land use and regulation).
146 L. Huntsinger
An increased population can also mean an increased positive presence on the
land. Local conservation areas will have a larger body of volunteers for restoration
work. Fire agencies will have more eyes on the land to watch for smoke. Lake
Taho e, in N eva da an d C ali for n ia, h a s ex p eri ence d a tre m end ous bu ild -up o f f uel s
in its forests. However, large fires are rare in part because the large number of peo-
ple in the area report fires quickly. One California rancher reported that in an area
where residents appreciated grazing for reduction of fire hazard, exurban residents
would notify him when a calf was in trouble or a fence was breached (Fried and
Huntsinger 1998).
Forest Considerations
Verti c a l s t r u c t u r e a n d s p e c i e s c o m p o s i t i o n a r e k e y e l e m e n t s o f e c o l o g i c a l i n t e g r i t y
in native forests (Yongblood, Max and Coe 2004) and, although readily measured
and managed, they can be difficult to retain in urban settings (Sanders 1984). For
example, a 48-year study of changes in forest canopy in a 16 ha remnant forest
patch in the New York Botanical Garden showed that overstory canopy composi-
tion had been significantly altered by changes in disturbance regime (Rudnicky and
McDonnell 1989). In addition, activities by local residents can contribute to the loss
of standing and down woody material (Matlack 1993), as well as changes in vegeta-
tion. Snags are commonly removed in areas with high recreation use or near houses
and roads because of concerns that they may fall. Logs and snags are often gath-
ered as firewood as well. Remnant native vegetation is sometimes manicured to be
more pleasing to the eye or easier for people to navigate by reducing the density
of the overstory and removing dead woody material (Tyrväinen, Silvennoinen and
Kolehmainen 2003). In forested areas, edges caused by development and roads tend
to be sunnier, warmer, drier, and more favorable to invasive nonnative species at the
expense of many native species.
In some exurban environments, efforts are made to save individual trees within
the development. Such trees are cut off from the network of ecological processes
that sustain them. Soil changes due to watering or soil compaction may eventu-
ally kill the trees. In addition, the trees are cut off from nutrient-cycling processes
that formerly took place underneath and around them. Pollinators, native to the for-
mer herbaceous vegetation, may not be able to locate scattered trees surrounded
by development. Without nearby habitats suitable for the growth of new trees, the
preserved trees will eventually simply die off.
On the other hand, remnant native forests can contribute significantly to main-
taining native species in an urbanizing landscape, especially if there is some
degree of connectivity to larger areas of forest and regulations restricting site alter-
ation (Heckmann, Manley and Schlesinger 2008). Despite an increase in non-
native species, remnant forests equal to or greater than 0.1 ha in size in the
Lake Tahoe basin retained much of their compositional and structural character
along a development gradient, including large tree density, total canopy cover, and
8 Into the Wild: Vegetation, Alien Plants, and Familiar Fire 147
plant species richness (Heckmann, Manley and Schlesinger 2008). One substan-
tive difference was the removal of downed woody material by local residents in
remnant forests. Remnant forests with high ground cover by native plants, high
canopy closure, and low ground disturbance may be less susceptible to inva-
sion by nonnative plants (Mandryk and Wein 2006; Merriam, Keeley and Beyers
Higher levels of human activity bring a variety of risks to the forest. In California,
patterns of sudden oak death seem to be related to the prevalence of human
recreation (Cushman and Meentemeyer 2008). Human activities such as construc-
tion, trenching, paving, sewage effluent disposal, insecticidal spraying of trees for
mosquito control, and road de-icing can promote disease by injuring trees (Ferrell
1996). Soil compaction from various human activities, including keeping horses and
other animals, can also degrade tree health by reducing leaf growth and changing
root morphology (Lambers, Chapin and Pons 1998).
The greatest challenge for exurban development in western forests is coping
with fire hazard. Many exurban developments are adjacent to public lands, where
forest management is seemingly always controversial and is not under the con-
trol of the community affected by it. Western forests generally have been sub-
jected to fire suppression for more than a century, resulting in ecological and
human safety problems, such as altered forest structure, increased tree density,
increased accumulation of dead wood, increased insect outbreaks, lowered biodi-
versity, and vulnerability to catastrophic fires (McKelvey and Johnson 1992; Ferrell
1996; McKelvey et al. 1996; Keeley, Lubin and Fotheringham 2003; Jensen and
McPherson 2008).
Within developed areas, landowners may choose quite different levels and types
of management for fire-hazard reduction and may or may not collaborate and plan
together to reduce the possibility of a conflagration. There is a typical pattern of
attitudes toward trees held by exurban residents: when they first move into the forest
they want to protect every tree. After living in an area for a while they begin to
see the danger of too many trees more clearly. The management of the Lake Tahoe
Basin is a case in point: management for fire-hazard reduction has been and remains
highly controversial, with some residents wanting fewer trees, some wanting more,
and much disagreement on the types of fuels reduction that are appropriate. The
scientific debate is also vociferous, with some arguing that fuel-reduction programs
increase invasion by nonnative plants and destroy wildlife habitat and others arguing
that there is no alternative, as fires are inevitable and the kinds that happen after
decades of fire suppression are far more damaging to air quality, wildlife habitat,
and plant communities than fuel treatments such as thinning, prescribed burning,
and brush crushing.
Unfortunately, forest fuel-reduction programs have the potential to enhance for-
est vulnerability to alien invasions. In part this is due to the focus on reestablishing
native fire regimes in a landscape that differs from pre-Euro-American landscapes in
the abundance of aggressive nonnative species (Keeley 2006). The common intro-
duction of nonnative plants may disrupt the ability of the forest to recover after a
fire, harvest, or thinning treatment.
148 L. Huntsinger
Rangeland Considerations
The author defines rangelands as woodlands, shrublands, and grasslands. Distur-
bance and fragmentation in shrublands at the edges of exurban or urban development
lead eventually to the complete replacement of the native vegetation and most of the
fauna by exotic plants and a combination of generalist native and exotic animals.
The first fragmentation event is often road construction, with associated housing
developments. Fuel breaks may be established and pose a special invasive plant risk
because they promote alien invasion along corridors into wildland areas (Keeley
2006). Later, habitat remnants may be subdivided by additional development. But
these isolated events are just the beginning. As described by Soulé, Alberts, and
Bolger (1992), trails soon appear, and vagrants and neighborhood children remove
the plant cover for camping sites and “forts.” The edges of the remnant are nibbled
by expanding gardens and back yards. These incursions are essentially irreversible
in scrub and chaparral-type associations because the vegetation is slow to reestablish
following removal. The proportion of core habitat in a fragment decreases over time,
and before long no point in the remnant is more than a meter or two from some kind
of artificial opening. These internal disturbances represent secondary fragmentation
that occurs within the larger scale fragmentation of the area.
In a study of the effects of fragmentation in a shrub habitat in California, effects
on plants and wildlife were found to go hand in hand. Extinctions after fragmenta-
tion occur quickly, with the least common species disappearing first. The size of the
remnant was the major predictor of extinction, with larger reserves generally supe-
rior for conserving species. In chaparral habitats in southern California, it was found
that in habitat remnants in the 10–100 ha range, only the most abundant chaparral-
dependent animal species survive for long, and most of these are doomed within
lative habitat disturbance and perhaps also because of changes in the frequency of
fire. In conclusion, Soulé, Alberts and Bolger (1992) argue that much more needs to
be learned about managing habitat remnants.
Exurban residents may plant species capable of naturalizing and moving out into
wildlands. The shrubs French broom (Genista monspessulana)andScotchbroom
(Cytisus scoparius)wereoriginallyplantedbyhomeownersfortheirhardinessand
showy yellow flowers. They have now spread throughout the west coast and cre-
ated new plant communities, thus changing the appearance of landscapes, shading
out native species, and altering soil characteristics to favor weedy, invasive species
(Vitousek et al. 1997).
Many shrubland ecosystems, such as intermountain west sagebrush steppe and
California chaparral, have natural, high-intensity crown fire regimes that do not mix
well with exurban development (Keeley 2006). A major contributor to increased
fire-suppression costs and increased loss of property and lives is the continued
urban sprawl into wildlands naturally subjected to high-intensity crown fires. Dif-
ferent shrublands have different kinds of fire regimes, however, requiring differ-
ent fire-management tactics, yet in most cases, our knowledge is far from adequate
(Keeley 2002).
8 Into the Wild: Vegetation, Alien Plants, and Familiar Fire 149
Shrub invasion can occur in western ecosystems as a result of fire suppression,
ultimately increasing fire risk. In the San Francisco Bay area, fire suppression and
reduced grazing have resulted in plant community change in the open spaces sur-
rounding the urbanized areas of the San Francisco Bay. There has been signifi-
cant conversion of grassland to shrubland dominated by coyote brush (Baccharis
pilularis). A significant increase in biomass resulting from the change from grass-
dominated to shrub-dominated communities was evident. Using fire modeling to
examine the effects of shrub increases on fire hazard showed that the replacement
of grass-dominated areas with shrub-dominated landscapes has increased the prob-
ability of high-intensity fires (Russell and McBride 2003).
On the other hand, frequent fires can obliterate the woody component of some
shrublands. For example, if fire occurs too often in sagebrush steppe, sagebrush
is unable to recover. Invasion by cheatgrass, as discussed previously, facilitates this
conversion. In chaparral, fires create opportunities for invasion of nonnative species.
There is considerable argument about the appropriate fire regimes in the various
shrubby regions of the west, but it is clear that fire regimes vary among ecosystems
(Jensen and McPherson 2008). In addition, the increasing presence of nonnative
species complicates predictions of fire outcomes.
Desert Considerations
In desert ecosystems, water is the key to life. Natural and artificial ponds and water-
ways may be focal habitat for plant communities that depend on consistent access to
water. Areas with water are rare and should be focal points for conservation. These
areas contain key habitats, have a high diversity of species in need of conserva-
tion, and are highly attractive to people for recreation and residence. Ranches and
farms typically center on water, and these areas are highly attractive for exurban
As development occurs in desert areas, land is re-contoured, vegetation is planted
or removed, road networks are built, and buildings are erected. New landscapes and
plant communities attractive to residents are created. In arid and semiarid ecosys-
tems, these designed, engineered ecosystems are often characterized by plantings
with high water demand, so water must be brought in from elsewhere. Assessing the
impacts of development on a wash in central Arizona, Roach et al. (2008) found that
the construction of canals created new flowpaths that cut across historic stream chan-
nels, and the creation of artificial lakes produced changed nutrient cycling. Further
hydrologic manipulations, such as groundwater pumping, linked surface flows to
the aquifer and replaced ephemeral washes with perennial waters. These alterations
of hydrologic structure are typical by-products of urban growth in semiarid regions.
Wash es ar e u sua lly di stu r bed o r tran sfo r med i nto dr ain a ge st r uct ure s , cha n gin g flood
disturbance regimes characteristic of these waterways and eliminating habitat for
desert vegetation (Stiles and Scheiner 2008).
Desert plant communities are slow to recover from the impacts of volunteer
roads, campsites, and plant removal, all of which can be associated with exurban
150 L. Huntsinger
development. Slow-growing desert plants such as ironwood (Olneya tesota), cre-
osote bush (Larrea tridentate), and saguaro cactus (Cereus giganteus)maybe
harmed directly by construction and roads. Plant theft and vandalism also increase
with an increased human presence and more roads. Erosion from roads and soil com-
paction increases, as planned roads are augmented by volunteer roads and off-road
vehicle tracks. These can serve as vectors for nonnative species introduction. Non-
native species that produce biomass and can support fires are especially dangerous
to desert ecosystems.
Species within deserts can respond to fragmentation in varied and potentially
contradictory ways. For example, contrary to expectations, low-density exurban
development benefits some species by providing water, forage, and shade; these
benefits disappear as housing density increases (Bock, Jones and Bock 2008).
One of the most important conclusions to be drawn from this review is that plan-
ning should consider ways to reduce the introduction and spread of nonnative plant
species. Nonnative plant species change the outlook for neighboring vegetation in
unpredictable ways. The changes wrought by the introduction of nonnatives can
be widespread, altering habitats, structure, species composition, and ecological pro-
cesses. The patterns of vegetation response and stability of the past become less use-
ful in predicting the outcomes of development. Retaining as much of the native flora
and ground cover as possible can help reduce the spread of nonnatives. Research
in forests, rangelands, and deserts supports the notion that invasive plants invade
more quickly when gaps in tree or plant cover are created, especially when this
exposes open ground. Encouraging or requiring use of native species for landscap-
ing within developments would be ideal, but seems unlikely to be implemented or
enterprises such as agriculture, grazing, or forestry lands is a good idea (Fig. 8.4).
These working landscapes ideally act as a buffer, providing a barrier to new nonna-
tive species and limiting the direct impacts of the activities of exurban residents. In
addition, such lands can help prevent the spread of wildfire to residences, because
crop, livestock, and forestry enterprises manipulate vegetation in ways that, if prop-
erly managed, can reduce fire hazard. In addition, prescribed burning and grazing
are still available as vegetation management tools on many of these lands.
waterways and wetlands. This reduces the possibility of flooding and also pro-
tects habitats that are often peak areas for wildlife activities, and important small-
scale plant habitats. In arid lands, water is of particular importance, and the associ-
ated habitats are relatively rare. Waterways, whenever possible, should be buffered
from the direct impacts of development and if possible, native flood disturbance
regimes should be allowed to continue. Vegetated riparian buffers contribute terres-
trial biomass to the aquatic food chain, regulate water temperature, control floods,
8 Into the Wild: Vegetation, Alien Plants, and Familiar Fire 151
Fig. 8.4 Rural working
landscapes can buffer
wildland and urban
environments. Photograph
by Lynn Huntsinger
provide wildlife habitat, and reduce erosion, sedimentation, and pollution (Perlman
and Milder 2005).
Fourth, for western ecosystems, planners should make the assumption that wild-
land fire is likely to occur. The costs of fire fighting and suppression should be taken
into account when determining where exurban development should take place. It is
unlikely that “natural” fire regimes will ever be restored in areas near or intermixed
with development because of the risks to residents and property, air quality concerns,
and the changes in the vegetation that have occurred because of fire suppression. If
employed, prescribed burning should be strategically designed to insure the most
efficient fire-hazard reduction and to minimize the amount of landscape exposed to
unnaturally high fire frequency (Keeley 2006). Leaving some overstory canopy and
minimizing exposure of bare ground may be less likely to promote nonnative plants
(Merriam, Keeley and Beyers 2006).
Fifth, development should strive to protect as much core habitat as possi-
ble. Various development strategies are proposed to minimize fragmentation and
edge effects. The ability of conservation development to protect biodiversity and
152 L. Huntsinger
ecosystem services depends on the size of remnant undeveloped areas, the amount
of change to natural disturbance regimes and ecological processes, and the relation-
ship of the exurban development to the rest of the landscape—whether remnants are
connected with larger wildlands, or whether the development abuts public lands, and
so forth. Ultimately, undeveloped fragment size affects the total number of individ-
uals present in a continuous patch of vegetation. Larger patches have more individ-
uals, which allows for larger populations and a lower extinction rate for the remnant
vegetation. Smaller patches have larger edges and lack buffer zones, so that their
limited expanse is exposed to repeated impacts from people (Stiles and Scheiner
Although it has been suggested that developments can be designed to reduce
impacts, for example by clustering dwellings, Lenth, Knight and Gilgert (2006)
found no evidence that cluster development had any impact on the proportion of
nonnative species found in remnant areas compared to more typical dispersed devel-
opment. Although the proportion of land area in clustered developments further
than 200 m from development was nearly twice that of dispersed housing devel-
opments, nonnative vegetation dominated both clustered and dispersed develop-
ments (Fig. 8.5). The habitat patches left undeveloped by clusters were significantly
smaller than those of undeveloped areas, and patches were often not connected. Sub-
urban edge effects may extend up to 200 m into grasslands and shrublands (Bock,
Bock and Bennett 1999; Odell and Knight 2001). Most of the open area in a typical
clustered development is within this zone, and as a result, edge species dominate.
Finally, the open spaces of clustered developments may not be managed in ways
that promote conservation values.
Fig. 8.5 This cluster
development retains patches
of open lands. Photograph by
Lynn Hunts inger
The value of clustered housing developments can be enhanced by planning
that connects clusters with each other or with other wildlands (Lenth, Knight and
Gilgert 2006). When possible, the location and configuration of open areas should
be planned on a regional scale, aggregating open-space areas and minimizing the
construction of roads and power lines. It is also possible that clustering homes may
8 Into the Wild: Vegetation, Alien Plants,and Familiar Fire 153
foster stronger community relationships, enabling collaborative community efforts
in the long run. Providing places where people will naturally meet each other helps
to develop a sense of community. Developed areas have an important role in the
maintenance of native ecosystems and the ability to maintain ecological integrity
will depend as much on the activities, practices, and politics of the local population
as on management conducted by land management agencies (Heckmann, Manley
and Schlesinger 2008).
An assessment of conservation-oriented limited development projects in the east-
ern United States found that they were protecting threatened conservation resources,
including rare biodiversity and ecosystem functions. They also resulted in signifi-
cantly more conservation benefits than other types of conservation developments,
including typical cluster developments (Milder 2007). On average more than 85% of
each site was protected as interior habitat, and project design and management gen-
erally addressed the conservation, restoration, and stewardship needs of site-specific
conservation targets (Milder, Lassoie and Bedford 2008). Despite containing rela-
tively little development, most are financially self-sustaining and many realize a
profit. The sale of a relatively small amount of subdivided land ready for con-
struction can finance the protection of a much larger amount of undivided land.
In addition, many of these developments benefit from federal, state, and/or local
tax incentives for land conservation (Milder 2007; Wright and Anella 2007). More
study of these kinds of options is needed.
Finally, it is important to remember that ongoing changes in plants, vegetation
structure, and climate make the exurban environment a true frontier, in the sense that
our ability to look beyond the boundaries of the present and anticipate the future is
limited. Turning back to the past for answers about how plant communities will
respond to future impacts is of limited use. To cope with this changing and new
world will require tough decisions, with special attention to decision-making pro-
cesses and to who is included in them. Planning should seek to maintain options for
vegetation management in order to be able to cope with the unanticipated changes
of the future.
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... The ecological impacts include decreased biodiversity, fragmentation of forests and wildlife habitat, and an inability to conduct management like prescribed burning to prevent wildfires. 11 New landowners may manage for habitat types other than the open grassland and savanna habitats typical of ranched landscapes. 12 Similar processes occur in forested landscapes. ...
... In one analysis of the 2008 data, landowners were grouped into four typologies according to ownership motivations. 11 The groups were distinguished by landowner motives centered on rural lifestyles, working landscapes, natural amenities, or financial investment. All but the financial-investment-oriented group considered living near natural beauty the most important or second most important reason for owning their land. ...
... All but the financial-investment-oriented group considered living near natural beauty the most important or second most important reason for owning their land. 11 Those with larger properties were also far more likely to consider income an important reason for owning their land, with more than 70% of those with more than 200 ha, compared to less than 20% of those with 1 to 9 ha, responding that income from the land was important to them. All groups considered land appreciation an important motive for owning their land. ...
On the Ground California landownerships are changing—becoming smaller and more amenity-driven, with important implications for ecosystem service production. Residence on the property, larger property size, source of income from the land, having a long-term outlook, and using an advisory service are associated with landowner management for ecosystem services for the owner and for society. Advisory services like Cooperative Extension and the Natural Resources Conservation Service, as well as private consultants and professional organizations, have an important role in the future of ecosystem service production.
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A social–ecological system (SES) is a combination of social and ecological actors and processes that influence each other in profound ways. The SES framework is not a research methodology or a checklist to identify problems. It is a conceptual framework designed to keep both the social and ecological components of a system in focus so that the interactions between them can be scrutinized for drivers of change and causes of specific outcomes. Resilience, adaptability, and transformability have been identified as the three related attributes of SESs that determine their future trajectories. Identifying feedbacks between social and ecological components of the system at multiple scales is a key to SES-based analysis. This chapter explores the spectrum of different ways the concept has been used and defined, with a focus on its application to rangelands. Five cases of SES analysis are presented from Australia, China, Spain, California, and the Great Basin of the USA. In each case, the SES framework facilitates identification of cross-system feedbacks to explain otherwise puzzling outcomes. While information intensive and logistically challenging in the management context, the SES framework can help overcome intractable challenges to working rangelands such as rangeland conversion and climate change. The primary benefit of the SES framework is the improved ability to prevent or correct social policies that cause negative ecological outcomes, and to achieve ecological objectives in ways that support, rather than hurt, rangeland users.
We examined the impacts of exurban development on bird communities in Essex County, New York and Madison County, Montana by comparing differences in abundance of songbirds between subdivisions and control sites in both regions. We hypothesized that impacts to bird communities would be greater in the relatively homogeneous, closed canopy Adirondack forest of northern New York State than they would be in the more naturally heterogeneous grasslands interspersed with trees and shrubs of the Greater Yellowstone Ecosystem. We examined birds in five functional groups expected to be responsive to exurban development, and determined relative abundance within subdivisions and control sites across these two distinct regions. We found little support for our hypothesis. For birds in the area-sensitive, low nesting, and Neotropical migrant functional groups, relative abundance was lower in subdivisions in the Adirondacks and in Madison County, while relative abundance of edge specialists was greater in subdivisions in both regions. The direction and magnitude of change in the avian communities between subdivisions and controls was similar in both regions for all guilds except microhabitat specialists. These similarities across diverse ecosystems suggest that the ecological context of the encompassing region may be less important than other elements in shaping avian communities in exurban systems. This finding suggests that humans and their specific behaviors and activities in exurban areas may be underappreciated but potentially important drivers of change in these regions.
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When attempting to value ecosystem services and support their production, two critical aspects may be neglected. The term "ecosystem services" implies that they are a function of natural processes; yet, human interaction with the environment may be key to the production of many. This can contribute to a misconception that ecosystem service production depends on, or is enhanced by, the coercion or removal of human industry. Second, in programs designed to encourage ecosystem service production and maintenance, too often the inter-relationship of such services with social and ecological processes and drivers at multiple scales is ignored. Thinking of such services as "social–ecological services" can reinforce the importance of human culture, perspectives, and economies to the production of ecosystem services. Using a social–ecological systems perspective, we explore the integral role of human activity and decisions at pasture, ranch, and landscape scales. Just as it does for understanding ecosystems, a hierarchical, multiscaled framework facilitates exploring the complexity of social–ecological systems as producers of ecosystem services, to develop approaches for the conservation of such services. Using California's Mediterranean rangelands as a study area, we suggest that using a multiscaled approach that considers the importance of the differing drivers and processes at each scale and the interactions among scales, and that incorporates social–ecological systems concepts, may help avoid mistakes caused by narrow assumptions about "natural" systems, and a lack of understanding of the need for integrated, multiscaled conservation programs.
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Comparative research into the human-maintained economic and ecological systems referred to as working landscapes is a rarity in the literature. Nonetheless, developing such comparisons is the end goal of this book. Altogether, 44 field scientists are contributing authors, with some appearing in multiple contributions, but others spelling out the specific knowledge crucial to just one part of a single chapter. In this final commentary, the book’s editors lay out the conclusions attained in this extended inquiry, suggest research needs and lessons learned, and raise the issue of policies that are needed, some urgently, to support oak woodland working landscapes. We recognize a number of takeaway lessons from this long-term project, including advances in economic analysis that make it possible to assess the total economic value of a landscape. We have come to, as we journeyed through the production of this volume, an overall conclusion that seems to us important: Just because two places appear similar hardly means that they are alike; oftentimes the variations are far more than skin deep. But with that as an initial concession, it pays to acknowledge how much can be learned from comparative research that matches physical, cultural, historical, economic, and geographical features, and then carefully places likenesses and departures side-by-side, in a deliberate attempt to learn across oceans, landscapes, economies, and societies.
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A large portion of the carbohydrates that a plant assimilates each day are expended in respiration in the same period (Table 1). If we seek to explain the carbon balance of a plant and to understand plant performance and growth in different environments, it is imperative to obtain a good understanding of respiration. Dark respiration is needed to produce the energy and carbon skeletons to sustain plant growth; however, a significant part of respiration may proceed via a nonphosphorylating pathway that is cyanide resistant and generates less ATP than the cytochrome pathway, which is the primary energy-producing pathway in both plants and animals. We present several hypotheses in this chapter to explore why plants have a respiratory pathway that is not linked to ATP production.
Conservation easements provide a surprising diversity of alternative strategies for maintaining the ranch.
We counted nesting songbirds for three summers on 62 200-meter-diameter plots on City of Boulder, Colorado, Open Space grasslands. Habitats included upland mixed-grass prairie and low-lands with tallgrass prairie and irrigated hayfields. Plots were located either at habitat edges adjacent to suburban developments or at least 200 meters interior to such edges. Grassland-nesting songbirds collectively were nearly twice as abundant on interior as on edge plots. Species significantly more abundant on interior plots, independent of habitat type, included Vesper Sparrow (Pooecetes gramineus), Savannah Sparrow (Passerculus sandwichensis), Grasshopper Sparrow (Ammodramus savannarum), Bobolink (Dolichonyx oryzivorus), and Western Meadowlark (Sturnella neglecta). By contrast, combined counts of five suburban species - American Robin (Turdus migratorius), European Starling (Sturnus vulgaris), Common Grackle (Quiscalus quiscula), House Finch (Carpodacus mexicanus), and House Sparrow (Passer domesticus) - were nearly five times greater on edge than on interior plots. If it is a goal to conserve native grassland birds on the western Great Plains, we conclude that grassland open-space systems in this region should be designed to reduce edges with suburban development. More research is needed to determine what causes edge effects, which might include increased nest predation, human interference with the nesting process, and increased competition with suburban species.
Vernal pools are seasonal ephemeral wetlands that fill and dry each year, and are one of the few low-elevation habitats in California which are dominated by native plant species. Vernal pools continue to be converted into agricultural lands and urban housing developments; as a result, many vernal pool taxa are now rare and endangered. This chapter reviews the geologic, hydrologic, and edaphic settings of vernal pools. It also examines the evolution of the vernal pool flora, autecological traits of vernal pool species, and diversity and classification of plant communities. The conservation and management of vernal pool ecosystems are also discussed.
Fire, both inevitable and ubiquitous, plays a crucial role in North American ecosystems. But as necessary as fire is to maintaining healthy ecosystems, it threatens human lives and livelihoods in unacceptable ways. This volume explores the rich yet largely uncharted terrain at the intersection of fire policy, fire science, and fire management in order to find better ways of addressing this pressing dilemma. Written in clear language, it will help scientists, policy makers, and the general public, especially residents of fire-prone areas, better understand where we are today in regard to coping with wildfires, how we got here, and where we need to go. Drawing on abundant historical and analytic information to shed new light on current controversies, Living with Fire offers a dynamic new paradigm for coping with fire that recognizes its critical environmental role. The book also tells how we can rebuild the important ecological and political processes that are necessary for finding better ways to cope with fire and with other complex policy dilemmas.