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a Natural Habitat Through Riparian Zone Restoration


is extremely important for the survival of all living things. Humans use freshwater
to “drink, clean, for irrigation, fishing and recreation, but also for
navigation, hydroelectric power generation and waste disposal” (Berger et al.
2017). However, although human life relies on water, the freshwater systems are
continuously polluted by dumping chemicals and waste, introducing invasive
species, clearing natural vegetation, adding nutrients via agricultural
processes, etc. (Berger et al. 2017). To continue to use freshwater ecosystems,
particularly streams and riparian zones, for all the benefits that they provide
for the human population, more care needs to be given begin to the freshwater
systems by reducing the amount of damage that they are subjected to and by
restoring the habitat that has been damaged. Stream restoration is the act of
restoring or regenerating a riparian zone (the area encompassing the interactions
between the freshwater aquatic and terrestrial environments) to achieve
multiple goals including: “to enhance water quality, to manage riparian zones, to
improve in- stream habitat, for fish passage, and for bank stabilization”
(Bernhardt et al. 2005). Riparian restoration is becoming more important due to
the increasing degradation of the country’s freshwater. In fact, in 2015, the
EPA reported that more than 40,000 miles of California’s rivers and streams are
currently threatened by pollution (Shadowski, 2016). And in 2005, a study
reported that “more than one- third of the rivers in the United States were
listed as impaired or polluted” (Bernhardt et al. 2005). Deciding on a riparian
restoration project has become a profitable business and often plays a role in
management of the environment and various policy decisions (Bernhardt et al.
2005). The movement towards freshwater restoration could be due to the benefits
that freshwater provides society. In addition, global restoration efforts of
riparian zones are completed on areas that have some sort of value such as
economic, cultural or spiritual (Roni et al. 2008). When successful, riparian zone
restoration can have a lot of great impacts on the environment. Focusing on two
goals of restoration: increased habitat heterogeneity and biodiversity and improved
hydrologic connectivity, the following paper will analyze the effectiveness of riparian
zone restoration techniques in a regeneration framework.

streams hold great biological value. They contain a very broad and rich biota
and are home to a vast diversity of fish, other vertebrates, microbiota and micro-
and megafauna (Malmqvist and Rundle, 2002). Additionally, running freshwater
habitats encase various niches and smaller ecological habitats from mountainous
springs to valley rivers (Malmqvist, 2002). The flora and fauna in these lotic
systems are very diverse and valuable, but they are also very vulnerable to
pollution, and loss of habitat heterogeneity and biodiversity can be attributed
to both instream activities and riparian zone activities (Bond and Lake, 2003).

habitat biodiversity is a valuable goal of most stream restoration projects and
there are different techniques of restoration that aim to increase the
heterogeneity. Some of these techniques include additions of large items such
as woody debris and boulders and small patches of gravel to increase habitat
for fish and invertebrates, and nutrient enrichment to improve biotic
production (Turunen et al. 2017, Roni et al. 2008). The addition of large woody
debris and boulders serves to increase habitat diversity by providing stable
habitats and new patches with complexity of flow patterns that add specific
niches to the stream community (Spanhoff and Arle, 2007). The addition of
boulders also leads to less sedimentation on the stream bed and, according to a
study by Turunen et al., (2017) excessive fine sediment buildup “reduces
habitat availability, for crevice- dwelling macroinvertebrates, impairs
salmonid spawning success and scour periphytic algae”. Therefore, in the same
study, the stream that had been restored with boulders had a higher
concentration of aquatic bryophytes and benthic macroinvertebrates than one
that had been restored with other materials. A meta study by Roni et al. (2008)
looked at the effectiveness of various stream restoration techniques reported
that in studies where log and boulder additions took place, the following
benefits in terms of macroinvertebrate populations were recorded: an increase
in abundance, an increase in population richness, increased biomass, and one
study showed that log additions create hot spots for primary producers.
However, small sediments and patches of gravel also have a place in streams and
the addition of these in stream restoration show benefit for both fish and
macroinvertebrate populations. For fish, the Roni et al. (2008) study of the
effectiveness of restoration techniques listed gravel addition to result in:
more spawning trout (as much as five times as many in one study), more spawning
Chinook salmon whose embryos had higher survival rates than those at unenhanced
sites, and a higher percentage of fish eggs surviving to the fry stage. And for
macroinvertebrates, it was found that gravel addition resulted in: increased
abundance of macroinvertebrates and in one study, “within 4 weeks, abundance
and biomass of macroinvertebrates on newly placed gravels was similar to or
higher than that of natural gravel deposits” (Roni et al. 2008)  The landscape attributes listed (boulders,
logs and gravel) naturally occur in these habitats, but increased anthropogenic
influence on these places changes the “proportional abundance of different
streambed substratum types” (Malmqvist et al., 2002). A reduction in variation
of ecological habitats within streams leads to a decrease in biodiversity and
heterogeneity making it important to re- establish these microhabitats.

interesting stream restoration technique is to add organic and inorganic
nutrients to “boost productivity of system to improve biotic production and to
compensate for reduced nutrient level” (Roni et al. 2008) The water chemistry
of a stream is extremely important, and it is not only the organisms living in
the stream that rely on the availability of nutrients but the communities of
plants and animals around the area. A paper written by Björn Malmqvist and
Simon Rundle (2002) lists the factors and some causes for the changing
chemistry of running freshwater to be acidification from industrial emissions,
nutrient addition from agriculture, toxic metals from mining, organochlorine
toxins from industrial use, organic pollution from urbanization and endocrine
disruptors from industry. Nutrient addition as a stream restoration technique
has proven to be effective in multiple ways for primary and secondary
production as well as for fish populations. Across multiple studies, the
recorded benefits of nutrient addition on primary and secondary producers was:
increased standing crop and biomass of periphyton, caddisfly population
increase, increase in macroinvertebrate biomass, and an increased growth rate
of macroinvertebrate collectors (Roni et al. 2008). For fish, the benefits were
seen in increased juvenile density, growth and survival, increased growth rates
of adults, increased neutral lipid storage in Thymallus arcticus, increased
salmonid biomass, and increased growth condition factor (Roni et al.2008). The
various nutrients added in the studies reviewed by Roni et al. (2008) include
inorganic nitrogen and phosphorus, chlorophyll, phosphoric acid, salmon
carcasses and analogs, and inorganic phosphate fertilizer. In a study by V.
Gulis and S. Suber (2003) in North Carolina, the leaves of two trees, Acer
rubrum and Rhodendron maximum were placed in two different reaches of a
headwater stream- one reach that was being continuously enriched with ammonium,
nitrate and phosphate and the other was not being enriched at all. The
researchers studied how the nutrient addition affected the decomposition of the
leaves and how the microbial community responded to the enriched habitat. The
scientists did this by recording the microbial restoration rate, biomass of
fungi and bacteria, the sporulation rate and the composition of the
hyphomycetes (a mold fungi) community (Gulis and Suber 2003).  The study found the decomposition of the
leaves to be faster, the respiration rates to be higher, an increase in the
fungal biomass, a higher sporulation rate and a higher number of hyphomycetes
species in the nutrient enriched zone (Gulis and Suber 2003). The study proved
that with the nutrient addition, the stream habitat was significantly more
productive. However, the addition of nutrients can be dangerous to the stream
habitat and should only be used in environments where organic and naturally
occurring nutrients have previously been tested at a very low rate. A potential
problem with nutrient addition restoration that freshwater streams face is
eutrophication, which is an excessive amount of nutrients added to a body of
water. Although this phenomenon might not be a problem if it were to happen
naturally, if it were to happen by the hand of human activities, then the
natural processes in the stream would be increased dramatically and the stream
may experience trophic cascading, which is essentially when predators in a food
chain suppress their prey and therefore, eliminate the pressure on the food
chain below their prey, throwing off the whole ecosystem (Zheng and Paul 2016).
Therefore, extra caution should be applied when considering nutrient addition
as a stream restoration technique.

the restoration technique of adding a landscape attribute and the addition of
nutrients aim to increase habitat biodiversity and heterogeneity. Within this
goal, one of the benefits discussed in the addition of landscape attributes
through stream restoration was an increase in the macroinvertebrate communities
and something to assess for before utilizing nutrient addition as a restoration
technique is stream health. Interestingly, the macroinvertebrate population of
a freshwater ecosystem can be a good indicator of water quality. In this
method, macroinvertebrates from the benthic community are designated as
indicator species put into categories of tolerant, facultative or intolerant
regarding their ability to withstand water pollution (Resh and Unzicker). These
designations allow researchers to survey the macroinvertebrate community in a
stream ecosystem and then determine the water quality and pollution level based
on the rating of the organisms found. This method has been used for quite some
time and has proven to be effective, so it gives good reason to pay attention
to the macroinvertebrate community within a stream ecosystem and, also gives
reason to maintain the health of that ecosystem.

second overall goal of stream habitat restoration is to improve hydrologic
connectivity. Hydrologic connectivity is the “water-mediated transfer of
matter, energy and/or organisms within or between elements of the hydrologic
cycle” (Pringle 2003). The benefits of stream connectivity include fish
migration, movement of nutrients from one geographic location to another, and
the general ability of moving freshwater to be purified through the process of
just running the stream course (Pringle 2003). Unfortunately, the freshwater in
the United States is being dammed and impounded at an extremely fast rate and
as of 2003, only 2% of the rivers in the United States remained free- flowing
(Pringle 2003). Hydrologic connectivity and dynamics are both very dependent on
flow regime and topography of the stream and river systems and this is seen in
the relationship between lying beneath the connectivity of floodplains with
mainstream rivers and headwaters (Kondolf et al., 2006). The disruption of the
connectivity through “levee construction, mainstem incision, or reduced floods
downstream from dams” can decrease the productivity of organisms on the
floodplain, it can negatively affect nutrient exchange from headwater to tributary
and it also affects the dispersal of biota, vertebrates other than fish, that may
use the stream to seek passage to the wetlands (Kondolf et al., 2006).  In this paper, fish migration needs, and
further benefits of hydrologic connectivity on the surrounding natural environment
will be focused on.

passage barriers, or structures such as dams and culverts are having a huge
impact on fish migration and therefore, are leading to “restricted range size,
reduced abundance, loss of genetic diversity and changes in community
composition” in fish species (O’Hanley et al. 2011). Large barriers such as
dams result in full blockage of fish movement, but small barriers also have an
effect on fish migration depending on the season and can also reduce access to
different parts of the stream to smaller fish at any time of the year (O’Hanley
and Tomberlin, 2005). The negative effects of preventing fish movement does not
end at just reducing fish migration but because of that fact, it also increases
“the level of inbreeding among resident fish, lowering nutrient inputs to
upstream reaches provided by the carcasses of anadromous adults and causing
artificial selection for stronger swimming fish species” (O’Hanley and
Tomberlin, 2005). Overall, this will negatively affect the biodiversity of the
stream, surrounding lakes, and possibly the overall freshwater network in a
given region. Because it seems implausible to take out all of the dams,
prioritizing smaller passage barriers can potentially have large effects and seems
to be the best option when planning a restoration project. As stated, even the
smaller barriers have a large impact on fish movement. To prioritize a
restoration project based on removal of fish passage barrier, O’Hanley and
Tomberlin (2005) have proposed a Fish Passage Barrier Removal Problem which is
an opportunity for the designer of the project to consider all of the barriers
that a fish may need to cross to go from one place to another, and the
increased passability rate should a current barrier be removed (O’Hanley and
Tomberlin, 2005). The researchers also state that other things may be
considered including the environmental quality, any threatened or endangered
species that must take precedent over another, any risk that the project may
pose and potential improvement for human consumption after the project is
completed (O’Hanley and Tomberlin, 2005). A different study done in British
Columbia looked at a stream that had been affected by a rockslide after the
implementation of the railroad in the area. The presence of the rocks made it
exceedingly difficult for the fish, especially the pink salmon, to make passage
upstream. When the barrier was removed, the salmon were able to reestablish
their spawning grounds and population and within two decades of the barrier
being removed, the pink salmon had fully restored their population in the
stream and even experienced larger than normal population growth rates (Pess et
al., 2011). This case study is a good example of a small barrier as minor as a
rock slide being removed and improving the population of one species of fish.
It also shows the resiliency of animals and their drive to succeed in the
habitat that they are in. Which gives meaning to restoration efforts and
specifically, the importance of having hydrologic connectivity for the health
of biotic species.

connectivity and keeping rivers free- flowing is important for fish species
migration but also proves to be beneficial for other reasons as well. Free-
flowing rivers and their interaction with the riparian zones around them are
crucial to the physical and chemical profile of the river itself and
surrounding area (fluvial system) (O’Hanley, 2011). Reasons for this include:
“stream discharge, depth and temperature of the stream, dissolved oxygen
content, suspended and bedload sediment transport, nutrients and large woody
debris supply, substrate composition and river and coastal morphology”
(O’Hanley, 2011). Natural stream and fluvial ecosystems are accustomed to
climate and weather- related happenings that would naturally occur in that area
however, when they are being held back by some sort of barrier, the ecosystem
can begin to change and when hit with something like a flood, although it may
normally occur, the fluvial ecosystem may be extremely affected by that
(O’Hanley, 2011). Including the drying up a stream altogether. In the example
of the San Joaquin River in California, the Friant Dam caused tributaries to
dry up completely, therefore losing that natural habitat (Kondolf et al., 2006).

paper written by Kondolf et al. (2006) argues that when tackling projects that aim
to restore stream habitat connectivity, it is important to re- establish the
connectivity in three different dimensions: longitudinal, latitudinal and vertical.
The researchers note that the interaction of these three dimensions underlie
almost all ecosystem processes and patterns in freshwater systems.  The paper includes description of a case study
of a restoration project that took place on the Merced River in California
where the longitudinal, latitudinal and vertical dimensions were not all met. The
Merced River in California was dammed up in the 20th century which
affected the migration of the salmon population upstream for spawning and also
affected the movement of necessarily spawning gravel downstream, which as
stated above, can be detrimental to salmon population success. When the
planners recognized that the dam was affecting the salmon population, they
attempted to restore the habitat by adding a hatchery and constructed riffles
using flat gravel beds, held in place by boulder weirs. However, because the
restored habitat was so different than what the salmon and trout would normally
spawn in- it was too flat and did not account for the preferred naturally occurring
riffles and pools- the area was only used for spawning at a 10% rate of what was
expected. This restoration project, although in good faith, failed to connect
the latitudinal, longitudinal and vertical aspects of the normally occurring habitat.
In other words, the dam itself was blocking the longitudinal connectivity, the
natural occurring riffles and pools were no longer present therefore blocking
the vertical connectivity and because the project involved narrowing the river,
it reduced lateral connectivity (Kondolf et al., 2006). The idea of three
dimensions of connectivity needing to work together is, as will be explained
later in this paper, similar to the concept of regenerative studies being the
overlap of multiple disciplines.

The aforementioned
case studies prove that the barriers affecting hydrologic connectivity are
changing the whole ecosystem of the stream and not just what species can move
up and down it, even further affecting the multitude of benefits that free-
flowing fresh water provide for society. Jesse R. O’Hanley of Kent Business
School explains the importance of fluvial systems and planning for barrier
removal in a lot of his work. In Open
rivers: Barrier removal planning and the restoration of free- flowing rivers,
O’Hanley (2011) argues that it is not always about taking out the largest
barrier but rather figuring out the passes that can be made to optimize the
restored habitat. He states that in addition to his solution methods which are
based on cost and optimum barrier removal, one could take into consideration
surface flow, sediment transport, fish population, community dynamic, and
bioeconomic models to evaluate the full benefits of the range of different
models based on environment, ecology and economy. He offers that an approach
like this would be multi- objective and by looking at the project in a bigger
scope, the best outcome could be achieved. This viewpoint is also reminiscent
of a definition of regenerative studies that called on multiple disciplines to
solve a problem.

habitat restoration were to be viewed through a definition of regeneration that
stated that a regenerative system: reused present materials, kept the future
generations in mind with a goal of not depleting natural resources, and promoted
an interest in the health of the environment, it would be considered a
regenerative cycle. Stream and riparian zone restoration are essentially acts
of regeneration in themselves because they are rejuvenating a landscape but
broken down, the following is how they fit into the different frameworks of a
regenerative system definition. A regenerative system is one that reuses
present materials and does not add any new ones, essentially a regenerative
system is a closed- loop system that reuses the byproducts as opposed to
wasting them like a degenerative system. The habitat restoration of a stream is
using the area that is provided to create something new instead of digging out
a brand-new channel and creating a stream or making a man- made lake. Although
technology and additional products may go into the restoration, like nutrient
addition or the addition of a boulder or log, these items are used by the
system itself- the stream habitat so they are not going to waste.

A regenerative
system keeps the future generation in mind with a goal of not depleting natural
resources. The overarching goal of stream restoration is to preserve the
natural habitat and the benefits that it provides to society. The goal is not
to lose that resource in all but to restore it and rejuvenate it so that hopefully
it will be around for years to come. And in this case, the goal of stream
restoration is to make sure that the area is not just around for human
consumption but for organism consumption as well. In the studies presented in
this paper, as well as many other studies of their kind, the research design
was to restore the habitat and monitor the way that future generations
responded and adapted to the changes. A common intention was to re- establish a
population successfully. Habitat restoration would not exist without this piece
of the definition for the very ideas behind it are based in the future.

A regenerative
system promotes an interest in the health of the environment. Stream and
riparian zones are so important to the health of human beings that it is hard
to not care about the health of them but, as is a common roadblock in connecting
human empathy with the environment, it may be that members of society have never
even see a natural free- flowing stream. With the implementation of stream and
riparian zone restoration, the chances of that happening are becoming much more
likely. Also, similarly to other regenerative systems, recognizing that human
impact is largely what caused current freshwater degradation is the first step
in restoring the world’s streams and maintaining that unique and diverse
ecosystem. Through the implementation of the techniques in this paper and others,
habitat restoration in the riparian zone is attainable and will in turn,
positively impact and benefit all involved. 

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