Environmental Engineering Reference
In-Depth Information
species in some cases (Christian et al. 1997, 1998; Hanowski et al. 1997), but they do not provide
a satisfactory substitute for original native forest (Christian et al. 1998). Similarly, perennial native
grasses such as
P. virgatum
can provide suitable habitat for some but not all grassland-dependent bird
species (Murray and Best 2003; Murray et al. 2003; Roth et al. 2005), which are in severe decline in
part because of native habitat loss (With et al. 2008).
6.3.2.1.3 Water Quality
The decreasing quality and quantity of fresh water is a global problem that is, in part, a result of the
progressive replacement of native habitat with “thirsty” human-dominated productive ecosystems.
For example, plantation forests established in inappropriate areas (e.g., historically nonforested
landscapes) can result in decreased regional water availability (Jackson et al. 2005). On the basis
of current information, present-day biofuel production in the United States is not thought to be a
significant stress on water availability; however, future expansion of bioenergy crops (particularly
corn) could place significant demands on scarce water resources with concurrent effects on water
quality because of fertilizer and pesticide application (NRC 2007). However, it should be acknowl-
edged that quantification of U.S. water supplies is currently inadequate (OSTP 2007). Although
plantations may use more water than some arable crops, if planted in historically forested areas,
regional water balances are likely to return to their “natural state”. For example, plantation forests
that have appropriate riparian buffers to mitigate against unwanted sediment introduction and
solar-induced temperature increases after harvesting have better water quality relative to adjacent
pastoral areas in New Zealand (Quinn et al. 1997). However, reduced forest rotation lengths for
woody biomass crops will increase the frequency of catchment disturbance rates and enhance the
risks of detrimental effects such as stream sedimentation and solar-induced temperature increases
on aquatic fauna.
6.3.2.2 system stability and landscape considerations
In addition to the unintended consequences of the establishment of biofuel plantations on bio-
diversity conservation, there are concerns that this could have other unforeseen consequences.
Although Lindenmayer's (2009) review addressed concerns about the establishment of plantations
for general climate change mitigation, they are equally applicable to plantations for biofuel produc-
tion. Plantations that are more liable to destruction by wildfire than the vegetation they replaced
(Thompson et al. 2007) are potentially counterproductive to the aims of increased carbon seques-
tration. Likewise, monoculture plantations are potentially more susceptible to insect and disease
problems than mixed plantings (Jactel and Brockerhoff 2007; Jactel et al. 2008). This may be the
case with native and exotic species. Such unintended potential consequences should be carefully
considered when crops are selected for biofuel production.
Apart from habitat loss, the fragmentation of remaining areas of natural habitat is considered a
main cause of biodiversity loss (Hunter 1990; Murcia 1995; Henle et al. 2004). Fragmentation can
alter species richness and abundance, increase biological invasions, and alter community structure
and ecosystem processes (Laurance et al. 2002). Small, isolated patches of habitat may be inad-
equate for larger species that require large territories to have access to sufficient food sources. Some
species avoid forest edges and occur only in core areas of habitat that are not present in smaller
fragments. For some migratory songbirds in the northern Great Lakes region, forest edges created
by logging increased breeding density and nesting failure, creating an ecological trap (Flaspohler
et al. 2001). Even small areas of nonhabitat can become barriers that are impassable. For example,
many Amazonian rainforest species avoid clearings of as little as 100 m width, which can lead to
greatly reduced dispersal (Laurance et al. 2002). Combined with the fact that fragmentation gener-
ally reduces the size of local populations, this affects reproduction and increases the risk of genetic
deterioration and extinction (Nason and Hamrick 1997; Fahrig 2001). For example, lizards in habi-
tat fragments have been found to exhibit reduced levels of allelic diversity, which is likely to cause
inbreeding depression or reduced recruitment (Stow and Briscoe 2005).
