Synthesis Paper: EAS 539
Adam E. Kaminsky
04.26.2025
How is the composition of riparian corridors changing in northern forests and how does this affect
spatial ecological function?
Forested riparian corridors, like all ecosystems in the modern world, are experiencing
dramatic anthropogenic changes, including those from human development, resource extraction,
and climate change. Riparian ecosystems are a critical point of connection between terrestrial and
aquatic environments. Due to this spatial characteristic, riparian forests experience frequent mild
disturbances from flooding, maintain a moist microclimate, and benefit from high nutrient influx
and productivity. These unique characteristics allow riparian forests to be disproportionately rich in
biodiversity (Graziano et al., 2022). As northern riparian forests are altered or destroyed by human
development and climate change, there are wide-reaching effects on the spatial ecological
function of these systems.
The changes predominantly affecting northern riparian forests can be broken into two broad
categories. First, riparian forests are directly lost or changed due to human activities, including
suburban and urban development, logging, mineral extraction, and agriculture. Second, riparian
forests are altered by climate change.
Within this first category, much of the literature focuses on the effects of logging, as logging
is one of the leading causes of northern riparian forest loss. Since riparian forests are often
intentionally preserved during logging operations, their size and shape are commonly determined
by policy decisions rather than ecological demands (Johnson, 2025). Traditionally, forest managers
construct a fixed-width buffer zone around riparian forests. These fixed widths are easy to design
and implement, but ignore localized spatial heterogeneity (Logan McClendon, 2025). Although
there is evidence to suggest that simply increasing the width of a buffer is correlated with increased
ecological function, there is a growing body of research indicating that small-scale heterogeneity in
riparian forests is also highly correlated with ecological function (Lim, 2025).
Many scientists are now proposing variable-width buffers based on localized hydrology and
ecology. Streams and rivers are surrounded by groundwater discharge sites arranged in a
heterogeneous mosaic around the main stem of water. Proponents of variable-width buffers point
to this heterogeneity as a reason to build site-specific buffers. (Clark, 2025). Forested areas with
groundwater discharge have significantly higher biodiversity than those without, meaning that
buffers preferentially built around groundwater zones have an outsized ecological impact
(Kuglerová et al., 2014). Furthermore, fixed-width buffers create homogenous forests in
unnaturally linear patterns, which result in diminished ecosystem function (Lim, 2025). Variablewidth buffers not only preferentially save important hydrological components of the ecosystem, but
also better mimic the natural heterogeneity of riparian forests (Holmes et al., 2017).
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Figure 1: One example of implementing variable-width buffers as a means of optimizing ecosystem
function in a heterogeneous landscape (Graziano et al., 2022).
Heterogeneity within riparian forests is important, but some studies claim that the
composition of the matrix surrounding riparian forests plays an even greater role in ecological
function. For instance, using bird community composition and structure as a measure of
ecosystem health, Rodewald and Bakermans (2006) examined riparian buffer zones with differing
surrounding matrices. They ran regressions of bird composition measured against both forest
width and matrix composition, and found that surrounding landscape type explained 94% of the
variation in bird communities, compared to only 6% explained by forest width alone (Rodewald &
Bakermans, 2006). Specifically, Rodewald and Bakermans found that both urbanized and
agricultural lands surrounding riparian forests led to diminished ecosystem function, often due to
an increase in invasive species, and changes to the forest structure. Importantly, they found that
the negative effects of surrounding development were significant even in very wide patches of
riparian forest, indicating how forest width alone is less important than the surrounding matrix. This
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study indicates that the matrix surrounding riparian buffers is an extremely important factor
determining ecosystem health in riparian forests.
The role of riparian forests within a broader matrix was further examined by Witing et al. in
2022. The authors developed a model to optimize riparian forest restoration in Belgium, and in the
creation of the model identified several key spatial components dictating riparian ecosystem
health. The model suggested that riparian forest function is greater with shorter distances between
patches, and larger upstream catchment basins. On the other hand, increased proportions of
agricultural and urban lands, as well as increased distance between patches were shown to
decrease ecological function. Furthermore, the model demonstrated how optimization methods
that prioritize forest restoration in headwaters regions had greater benefits than those that
prioritized restoration lower in the watershed (Witing et al., 2022). Overall, this model
demonstrated how riparian forest patches have the highest ecological function when more closely
linked to one another and with less surrounding urbanized and agricultural land. It also determined
that protecting riparian forests closer to the headwaters had an outsized impact on watershed
conservation as a whole.
Figure 2: Visualization of every conservation scenario developed by the model. The y-axis
represents agricultural potential of a given scenario, meaning how much land was put towards
agriculture. The x-axis represents a metric of stream health (the EPT index). As more land is
allocated towards agriculture, stream health, riparian carbon processing, and functional diversity
all decrease.
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Beyond logging, agriculture, and urban development, riparian forests are affected by
mining. Mining activities often lead to significant water contamination (Hoppenreijs et al., 2022), as
well as dramatic alterations to the hydrological regime through stream channel alteration, tailing
pond development, and groundwater pumping (Backstrand, 2025). Furthermore, mining projects
require road networks and other land use alterations that fragment riparian ecosystems
(Backstrand, 2025). Specifically, fragmentation due to mining in northern forests dramatically
increases the edge effect in riparian forests (Frelich, 2019). Along the edges of patches, increased
sun and wind are able to penetrate deep into the forest, resulting in significant changes to the
microclimate of the patch (Johnson, 2025) Furthermore, species composition changes significantly
with an increase in edge effect, largely due to an increase in invasive species (Hoppenreijs et al.,
2022). This fragmentation due to mining also impacts animal movement, leading to negative
consequences on communities of mammals, birds, and amphibians alike (Frelich, 2019).
In addition to direct fragmentation by humans, climate change is a major factor contributing
to northern riparian forest change over time. As the planet warms, weather patterns are becoming
more extreme, with higher intensity rainfall and longer periods of drought affecting northern riparian
forests (Logan McClendon, 2025). Flood events in particular are becoming more intense, leaving
riparian forests susceptible to damage from floodwaters. Likewise, as droughts become more
prolonged, water tables are lowered in riparian forests, which in northern climates is exacerbated
by a drop in snowpack due to climate change. The roots of riparian plants are particularly
susceptible to drought damage, meaning they are poorly adapted to the drying climate (Jarrett,
2025). Whether from extreme flooding or extreme drought, riparian forests are being lost to climate
change.
Another effect of climate change stems from fire. Most northern forests are adapted to a
particular fire regime, but the combination of fire suppression policy and climate change is altering
fires to become more frequent and much more severe (Bailey, 2025). The interaction between
riparian forests and fire is poorly understood. Studies suggest that, depending on climatic
conditions, riparian forests can act as both barriers preventing the spread of fire and corridors
promoting it (Pettit & Naiman, 2007). However, this dynamic has not been well studied with respect
to climate change. One exception to this knowledge gap comes from the seminal paper by Fairfax
and Whittle in 2020, in which they demonstrated how beaver-affected riparian forests consistently
block the spread of wildfires. As beavers actively expand riparian corridors, they help to push back
against the broader trend of riparian forest loss due to human activity, and increase forest resilience
to climate change (Fairfax & Whittle, 2020).
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Figure 3: Aerial images showing beaver affected riparian corridors in relation to fires. In the first
photo, the beaver affected stream retains vegetation after a fire, while the unaffected riparian
corridor is completely burned. In the second set of photos, the area directly adjacent to beaver
activity is spared while everything else is burned.
The literature broadly concludes that climate change is fragmenting riparian forests and
changing their species composition. However, the spatial specifics of this fragmentation, as well
as the effects on spatial ecological function, are not well described. An understanding of the
spatial distribution of climate-affected riparian forests, as well as the parameters determining
susceptibility or resilience of riparian forests would help managers adapt to the changing climate.
Some of this information has been described in the context of species migration. As
climate change affects the globe, many species are forced to migrate in search of favorable climatic
conditions. Riparian forests often span climatic gradients, and are relatively cool and moist
compared to the surrounding environments, allowing them to form the preferred migration route for
many species (Mishra, 2025). In a study by Krosby et al. in 2018, the authors discovered that the
most effective riparian migration corridors spanned large temperature gradients, had high canopy
cover, large relative widths, low exposure to solar radiation, and low levels of human modification
(Krosby et al., 2018). Human development of riparian forests directly reverses many of these
metrics, leading to a direct loss of ecological function and climate resilience. However, Krosby et
al. determined that the effects of humans are not spread evenly throughout the landscape. In fact,
the proportion of protected riparian forests is significantly larger in mountainous terrain compared
to in valleys and flat terrain (Krosby et al., 2018). This led Krosby et al. to recommend that
policymakers and land managers focus conservation efforts on valleys and flat terrain, where those
efforts have the highest potential for ecological benefit. Krosby et al. focused their investigation on
animal migration, but it would be interesting to expand their study to the slow migration of plant
species. Perhaps as the climate becomes hotter and drier, the relatively cooler and wetter riparian
forests can become refugia or migration corridors for plants.
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Figure 4: Maps showing riparian corridor scores (top) and GAP Status (bottom). For the riparian
corridor scores, darker colors indicate higher quality corridors. The left map shows individual
scores while the right map shows averages across watersheds. For the GAP status (legal
protections), darker greens are fully protected and bright green is unprotected. The left map shows
individual scores for the pacific northwest, while the right shows scores within ecoregions.
Comparing the top and bottom maps, it becomes clear that the highest scoring corridors are largely
in protected areas. However, some high scoring areas are completely unprotected, providing
places for managers to focus on for conservation (Krosby et al., 2018). A visual that scored high
priority areas against their protected status would have made this analysis much easier.
Riparian forests have undergone dramatic changes as humans develop the world and
change the climate. Much of this change comes from fragmentation and dramatic alterations to
the matrix in which riparian forests exist. However, the structure of fragmentation from different
causes is largely unknown. Likely, the spatial configuration of fragmentation differs by cause,
leading to differing effects on the fragmented landscape. A study comparing the matrices of
riparian forests fragmented by different human activities might help the scientific community gain a
more thorough understanding of these dynamics.
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Because riparian forests are such an important linkage between land and water, the effects
of changes to riparian forests extend far beyond the resident species. The extent of riparian forest
change and the effects of those changes have been examined through the lens of landscape
ecology, but more research is needed to gain a better understanding of these trends. Specifically,
many of the studies examining this topic are reliant on modeling, which comes with many
assumptions that limit its applicability. Thus far, the models have tended to rely on complicated
metrics of ecosystem health, making it hard to interpret concrete effects of riparian forest change
on specific species or populations. To best understand riparian forest change, more observational
and empirical studies should be conducted to tease apart the complex relationships influencing
riparian forest change, and more specific effects should be investigated. These studies might
provide vital information regarding the changing forests, and could also inform future models to be
more accurate and widely applicable. Landscape ecologists are uniquely suited to conducting this
research, as their focus on the spatial and human dimensions of ecology directly relate to the
scope of change affecting northern riparian forests. As land managers increasingly turn to riparian
forests as a key component of climate resilience, they will be increasingly reliant on the data
provided by studies in landscape ecology.
References:
Backstrand, S. (2025, March 30). Mining, Northern Forests, and Riparian Corridors. Class Blog EAS
539.
Bailey, J. (2025, April 12). Edge effects of wildfire and riparian buffers along boreal forest streams.
Class Blog EAS 539.
Clark, I. (2025, March 29). Digital elevation models have improved our understanding of species
composition drivers in boreal riparian zones and updated our management
recommendations. Class Blog EAS 539.
Fairfax, E., & Whittle, A. (2020). Smokey the Beaver: Beaver-dammed riparian corridors stay green
during wildfire throughout the western United States. Ecological Applications, 30(8), e02225.
https://doi.org/10.1002/eap.2225
Frelich, L. E. (2019). Terrestrial Ecosystem Impacts of Sulfide Mining: Scope of Issues for the
Boundary Waters Canoe Area Wilderness, Minnesota, USA. Forests, 10(9).
https://doi.org/10.3390/f10090747
Graziano, M. P., Deguire, A. K., & Surasinghe, T. D. (2022). Riparian Buffers as a Critical Landscape
Feature: Insights for Riverscape Conservation and Policy Renovations. Diversity, 14(3).
https://doi.org/10.3390/d14030172
Holmes, S. B., McIlwrick, K. A., Kreutzweiser, D. P., & Venier, L. A. (2017). Riparian Partial Harvesting
and Upland Clear Cutting Alter Bird Communities in a Boreal Mixedwood Forest. Forests, 8(5).
https://doi.org/10.3390/f8050141
Hoppenreijs, J., Eckstein, L., & Lind, L. (2022). Pressures on Boreal Riparian Vegetation: A Literature
Review. Frontiers in Ecology and Evolution, 9. https://doi.org/10.3389/fevo.2021.806130
Jarrett, S. (2025, March 29). Changing of riparian corridors and potential impacts on northern
forests. Class Blog EAS 539.
Johnson, A. (2025, March 30). Impacts on riparian microclimates due to logging. Class Blog EAS
539.
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Krosby, M., Theobald, D. M., Norheim, R., & McRae, B. H. (2018). Identifying riparian climate
corridors to inform climate adaptation planning. PLOS ONE, 13(11), e0205156.
https://doi.org/10.1371/journal.pone.0205156
Kuglerová, L., Ågren, A., Jansson, R., & Laudon, H. (2014). Towards optimizing riparian buffer zones:
Ecological and biogeochemical implications for forest management. Forest Ecology and
Management, 334, 74–84. https://doi.org/10.1016/j.foreco.2014.08.033
Lim, D. (2025, April 7). More Dynamic Riparian Buffer Strategies Improve Riparian Corridors’
Ecological Functions for Birds. Class Blog EAS 539.
Logan McClendon, A. (2025, April 12). Hydrological Connectivity and the Changing Composition of
Riparian Corridors in Northern Forests. Class Blog EAS 539.
Mishra, S. (2025, March 29). Edge Effects of Changing Composition in Riparian Corridors of
Northern Forests and Their Ecological Impact. Class Blog EAS 539.
Pettit, N. E., & Naiman, R. J. (2007). Fire in the Riparian Zone: Characteristics and Ecological
Consequences. Ecosystems, 10(5), 673–687. https://doi.org/10.1007/s10021-007-9048-5
Rodewald, A. D., & Bakermans, M. H. (2006). What is the appropriate paradigm for riparian forest
conservation? Biological Conservation, 128(2), 193–200.
https://doi.org/10.1016/j.biocon.2005.09.041
Witing, F., Forio, M. A. E., Burdon, F. J., Mckie, B., Goethals, P., Strauch, M., & Volk, M. (2022).
Riparian reforestation on the landscape scale: Navigating trade-offs among agricultural
production, ecosystem functioning and biodiversity. Journal of Applied Ecology, 59(6), 1456–
1471. https://doi.org/10.1111/1365-2664.14176
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