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\begin{document}

\title{The fluid definition of the `waters of the United States': Non-uniform
effects of regulation on US wetland protections}



\author[1]{Jeffrey Wade}%
\author[1]{Christa Kelleher}%
\author[2]{Adam Ward}%
\author[3]{Rebecca Schewe}%
\affil[1]{Syracuse University}%
\affil[2]{Indiana University Bloomington School of Public and Environmental Affairs}%
\affil[3]{Syracuse University Department of Sociology}%


\vspace{-1em}



  
  \date{June 17, 2024}


\begingroup
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\selectlanguage{english}
\begin{abstract}
Recent revisions to the definition of the ``waters of the United
States'' (WOTUS) have considerably altered how wetlands are federally
regulated under the Clean Water Act. The two most recent modifications
to WOTUS, the Clean Water Rule (CWR) and the Navigable Waters Protection
Rule (NWPR), represent two opposing approaches to the federal wetland
policy. Despite their implementation, the impacts of these rules on the
regulation of wetlands have as of yet been poorly characterized at broad
spatial scales. Using New York State (NYS) as a case study, we evaluated
the jurisdictional statuses of more than 373,000 wetlands under the CWR
and the NWPR to assess the landscape-scale effects of WOTUS
re-definitions. We found that statewide and within each of NYS's
hydrologic regions, the NWPR protects fewer wetlands and less total
wetland area than the CWR. The efficacy of the two regulations varied
considerably in space across NYS, highlighting the need for
comprehensive, nationwide assessments of wetland policy outcomes. We
also observed that both rules produced non-uniform patterns in
jurisdiction across a range of landscape positions and wetland sizes,
preferentially protecting large wetlands close to the stream network.
This effect was particularly pronounced under the NWPR, which excludes
all geographically isolated wetlands from protection. Our findings in
NYS emphasize the existence of unique patterns in protected wetlands
across spatial scales, highlighting the value in applying geospatial
analyses to evaluate environmental policy.%
\end{abstract}%



\sloppy


\textbf{The fluid definition of the `waters of the United States':
Non-uniform effects of regulation on US wetland protections}

\textbf{Running Title:} Non-uniform impacts of WOTUS regulation

Jeffrey Wade\textsuperscript{1}, Christa Kelleher\textsuperscript{1,2},
Adam S. Ward\textsuperscript{3,4}, Rebecca Schewe\textsuperscript{5}

1: Department of Earth and Environmental Sciences, Syracuse University,
Syracuse, NY, USA

2: Department of Civil and Environmental Engineering, Lafayette College,
Easton, PA, USA

3: O'Neill School of Public and Environmental Affairs, Indiana
University, Bloomington, IN, USA

4: Department of Biological \& Ecological Engineering, Oregon State
University, Corvallis, OR, USA

5: Department of Sociology, Syracuse University, Syracuse, NY, USA

\textbf{Keywords:} wetlands, WOTUS, Clean Water Act, Clean Water Rule,
Navigable Waters Protection Rule, regulation, geographically isolated,
New York

\textbf{Data Availability Statement}

The data that support the findings of this study are openly available in
CUASHI Hydroshare
(\emph{http://www.hydroshare.org/resource/b9ef542ef9e84ebdad7fe05f0ee95110}).

\textbf{Acknowledgments}

This work was supported by Grant No. 2017-05390/Project Accession No.
1015116 from the USDA National Institute of Food and Agriculture. Adam
S. Ward's time was supported by Department of Energy award DE-SC0019377,
NSF Award EAR 1652293, the Burnell and Barbara Fischer Fellowship, and
the Fulbright -- University of Birmingham Scholar program.

\textbf{Abstract:}

Recent revisions to the definition of the ``waters of the United
States'' (WOTUS) have considerably altered how wetlands are federally
regulated under the Clean Water Act. The two most recent modifications
to WOTUS, the Clean Water Rule (CWR) and the Navigable Waters Protection
Rule (NWPR), represent two opposing approaches to the federal wetland
policy. Despite their implementation, the impacts of these rules on the
regulation of wetlands have as of yet been poorly characterized at broad
spatial scales. Using New York State (NYS) as a case study, we evaluated
the jurisdictional statuses of more than 373,000 wetlands under the CWR
and the NWPR to assess the landscape-scale effects of WOTUS
re-definitions. We found that statewide and within each of NYS's
hydrologic regions, the NWPR protects fewer wetlands and less total
wetland area than the CWR. The efficacy of the two regulations varied
considerably in space across NYS, highlighting the need for
comprehensive, nationwide assessments of wetland policy outcomes. We
also observed that both rules produced non-uniform patterns in
jurisdiction across a range of landscape positions and wetland sizes,
preferentially protecting large wetlands close to the stream network.
This effect was particularly pronounced under the NWPR, which excludes
all geographically isolated wetlands from protection. Our findings in
NYS emphasize the existence of unique patterns in protected wetlands
across spatial scales, highlighting the value in applying geospatial
analyses to evaluate environmental policy.

\textbf{1.0 Introduction}

Since the expansion of the Clean Water Act (CWA) in 1972, the federal
protection of wetlands and rivers in the United States has been governed
by the debated and fluid definition of the ``waters of the United
States'' (WOTUS). Wetlands are crucial components of terrestrial
landscapes, providing numerous benefits that include biological habitat,
floodwater attenuation, biogeochemical processing, and sediment
retention (Acreman \& Holden, 2013; Capps et al., 2014; Cheng \& Basu,
2017; Lane et al., 2018). Despite these widely recognized benefits,
wetlands have been disregarded, destroyed, and filled for economic
benefit over the past 200 years (e.g., Dahl, 1990; Davidson, 2014;
Golden et al., 2019; Hey \& Philippi, 1995; Van Meter \& Basu, 2015),
resulting in subsequent losses of ecosystem services (e.g., Zedler,
2003). Under the CWA, jurisdiction waters (WOTUS) require permits for
pollutant discharges, dredging, or filling, while non-jurisdictional
waters are afforded no such protections at the federal level. The extent
of WOTUS has been ill-defined for more than 50 years, evolving through a
series of legal cases and iterative rulemaking that have yielded an
operational definition (Walsh \& Ward, 2019; Walsh and Ward; In Review).
Unlike laws that require legislative initiative, the definition of WOTUS
is embedded in the rulemaking process of the executive branch, leaving
operational definitions to be established by regulatory agencies (in
this case, the USEPA and USACE). Through many high-profile judicial
decisions and executive revisions, the extent of WOTUS has seen
continual evolution and interpretation (Walsh \& Ward, In Review).

The last decade has seen two redefinitions of WOTUS, resulting in
significant changes to the federal protection of wetlands in the US.
First, the 2015 Clean Water Rule (CWR) attempted to reconcile prior
Supreme Court rulings (\emph{United States v. Riverside Bayview Homes} ,
1985; S\emph{olid Waste Agency of Northern Cook County v. USACE} ,
2001,\emph{Rapanos v. United States} , 2006) into a clear-cut regulatory
framework that was both consistent and easily interpretable (USDOD and
USEPA, 2015). In addition to protecting intermittent and ephemeral river
systems, the CWR classified adjacent waters and wetlands into
jurisdictional categories using buffer distances from other protected
waters. Leaving room for scientific interpretation, the CWR also
codified the ``significant nexus test'', mentioned in \emph{Solid Waste
Agency of Northern Cook County v. U.S. Army Corps of Engineers} (2001)
and reaffirmed in Justice Kennedy's concurring opinion in \emph{Rapanos
v. United States} (2006). Under the significant nexus test, protections
are extended to adjacent water and wetlands on a case-by-case basis if
they ``significantly affect the chemical, physical, and biological
integrity'' of adjacent navigable waters, taken alone or in combination
with similarly situated waters (\emph{Rapanos v. United States} , 2006).
In response to these changes to the WOTUS definition, 31 states and a
variety of other plaintiffs pursued legal action to oppose the
enforcement of the CWR (e.g., \emph{Georgia v. Pruitt} ,
2018;\emph{North Dakota v. USEPA} , 2015; \emph{Texas v. USEPA} , 2018;
USDOD and USEPA, 2019). After litigation and numerous preliminary
injunctions, the CWR remained enforceable in only 22 US states,
including New York (CRS, 2019). A new rulemaking process, intended to
revise the CWR, was initiated via executive order in 2017 (Exec. Order
No. 13778, 2017).

In 2019, the CWR was repealed and by April of 2020 replaced by the
Navigable Waters Protection Rule (NWPR). To promote economic growth and
development and to reduce regulatory uncertainty, the NWPR sought to
redefine the legal term `navigable waters' consistent with the opinion
authored by Scalia et al. in \emph{Rapanos v. United States} (2006). The
NWPR restricted federal protections to waters that contribute flow to a
traditionally navigable waterway or sea in a typical year (USDOD and
USEPA, 2020). The updated rule also eliminated the significant nexus
test, requiring wetlands to receive continuous surface flow from other
jurisdictional waters to be considered jurisdictional. This redefinition
of WOTUS under the NWPR was vacated by \emph{Pasqua Yaqui Tribe v. USEPA
(2021} ). With the CWR repealed and NWPR struck down, federal wetland
protections in the US have presently reverted to the regulations
codified by the USEPA and USACE in 1986 (USDOD, 1986), though new
rulemaking has been initiated (USDOD and USEPA, 2021).

Given the recency and fluidity of ongoing revisions to US federal water
policy, few studies have assessed how the evolving definitions of WOTUS
have altered the protection of wetlands (Sullivan et al., 2020). While a
limited number of past studies have considered the protection of
wetlands at the watershed scale (Walsh \& Ward, 2019; Meyer \&
Robertson, 2019), additional work is still needed to characterize the
complex implications of these changes to federal water policy, as the
services provided by wetlands are non-uniform and vary considerably as a
function of spatial location (Cohen et al., 2016; Lane et al., 2022;
Marton et al., 2015) and size (Cheng \& Basu, 2017; Ghermandi et al.,
2010). This need is even more pressing given that the USEPA and USACE
have indicated that a WOTUS revision will occur in the near future
(USEPA, 2021). Thus, our objective in this study is to document how
changes to the legal definition of WOTUS under the CWR and NWPR alter
which wetlands are protected as a function of their landscape position
and size. To achieve this objective, we use the wetland-dense state of
New York (NYS) as a case study to demonstrate how changing regulatory
language can yield patterns of protection that are biased against
particular types of wetlands. Through regional analysis, we contribute
to the evolving discourse assessing the implications of WOTUS definition
revisions for wetland protections. We also provide additional discussion
to contextualize the controversial nature of federal wetland protection
and policy amongst numerous competing interests.

\textbf{2.0 Methods}

To date, few studies have investigated how the regulatory shift from the
CWR to the NWPR has impacted US watersheds (Meyer \& Robertson, 2019;
Walsh \& Ward, 2019; Walsh and Ward, In Review). We take NYS as a case
study (Figure 1), providing an assessment in the northeastern US that
spans multiple ecoregions and drains to multiple endpoints (including
the Great Lakes, Susquehanna and Delaware River basins, and the Atlantic
Ocean). The approach used in this study, following prior work of Walsh
\& Ward (2019, In Review) and Meyer \& Robertson (2019), leverages
several publicly available datasets to classify the jurisdictional
status of wetlands in New York. We quantified the federal protections of
more than 373,000 non-marine wetlands present in the US Fish and
Wildlife Service's National Wetland Inventory (NWI), covering over
876,000 ha across the state of New York (U.S. Fish and Wildlife Service,
2021). We excluded wetlands classified as estuarine or marine in NWI
records. Wetlands smaller than 0.01 ha in size were also omitted from
further analysis. We selected this threshold to minimize the inclusion
of small wetland fragments adjacent to larger contiguous wetland
polygons. We summarize wetland protection statuses state-wide and at a
smaller regional scale (defined by USGS HUC--6 basins; Figure 1). Given
that most investigations of wetland policy are performed at the
watershed scale, our analysis allows for an evaluation of policy
outcomes across a range of broader spatial scales.

As the jurisdictional status of wetlands primarily stems from their
proximity to streams, the identification of the location of the stream
network is a key task in the evaluation of WOTUS protections. Previous
approaches (e.g., Walsh \& Ward, 2019) used topographically-based flow
accumulation methods to estimate the spatial extent of the stream
network. We instead chose to define the stream network using the USGS
National Hydrography Dataset (NHD; 1:24,000 scale, Model Version 2.2.1),
as we could not ensure the reliability and accuracy of a
topographically-generated network at the geographic scale of NYS (U.S.
Geological Survey, 2020). While the NHD may underestimate stream network
extent (Elmore et al., 2013), the NHD does provide a consistent and
validated record of the location of streams within our study area and
across most regions in the US (Meyer \& Robertson, 2019). We used NHD
waterways as the basis for the location of the stream network in both
the CWR and NWPR scenarios. This may result in a conservative estimate
of the jurisdictional stream network under the CWR as the version of the
NHD used here only maps perennial and intermittent streams in NYS (U.S.
Geological Survey, 2020). Thus, we assume the NHD network is
representative of the network with flow during a typical year for the
NWPR scenario and serves as a conservative lower bound for the stream
network in the CWR scenario.

To define the protection status of each wetland within NYS, we
translated the regulatory procedures of the CWR and NWPR into a set of
geospatial analysis steps within ArcGIS Pro (Version 2.6.0). Using this
process, we classified each NWI wetland as jurisdictional,
non-jurisdictional, or requiring the application of the significant
nexus test (abbreviated as `significant nexus') for each regulation
based on the spatial relationships of each wetland to the stream
network. Under the CWR, wetlands located (1) within 100 ft (30.5 m) of a
jurisdictional water, (2) within both 1500 ft (457.2 m) of a
jurisdictional water and the 100-year floodplain, or (3) within 1500 ft
(457.2 m) of a traditionally navigable waterway are considered
jurisdictional by rule. As US wetland regulations are based around
imperial system units, we report these values first, followed by SI
units in parentheses. We applied a spatially continuous floodplain map
(Woznicki et al., 2019) to estimate the location of the 100-year
floodplain in our study area, as the commonly used Federal Emergency
Management Agency (FEMA) floodplain dataset was incomplete across NYS.
To identify the extent of traditionally navigable waterways, we used
publicly available streamflow information and channel geometry from the
USGS to create discharge-depth regression relationships across New York
State. We defined `traditionally navigable' waterways as those receiving
at least a median of 0.30 m of inundation per year (following Walsh and
Ward, 2019). All wetlands that do not satisfy the aforementioned
jurisdictional criteria but are located within 4000 ft (1219.2 m) of
another jurisdictional water are subject to the significant nexus test
under the CWR. Given the challenge in applying the case-by-case
significant nexus test to broad spatial scales, we were unable to
determine the precise extent of jurisdictional wetlands when evaluating
the CWR. Instead, depending on the results of site-specific significant
nexus determinations made by the USEPA and USACE, the percentage of
jurisdictional wetlands under the CWR may vary considerably. Wetlands
located further than 4000 ft (1219.2 m) away from a jurisdictional water
are considered non-jurisdictional by rule and are afforded no protection
by the CWR. While not directly assessed in this study, the CWR also
considers the impacts of `similarly situated waters', effectively
assessing aggregate impacts from several wetlands.

In contrast to the buffering approach used by the CWR, the NWPR defines
protections based on a surface-water connection between wetlands and the
jurisdictional stream network. The rule eliminates the significant nexus
test, instead classifying wetlands as either jurisdictional or
non-jurisdictional. For the NWPR scenario, wetlands were considered
jurisdictional only if they directly intersected the jurisdictional
stream network, simulating a surface-water connection. While we
acknowledge that this intersection approach does not necessarily
guarantee federal jurisdiction based on the NWPR, as we cannot confirm a
continuous surface connection at the scale of this analysis, we take
this as a reasonable estimate for protection.

\textbf{3.0 Results}

\textbf{3.1 The NWPR Decreases Wetland Protections Across NYS Compared
to the CWR}

In NYS, the NWPR guarantees protections for considerably fewer wetlands
by both total area and number when compared to the CWR (Figure 2). Under
the CWR, 88.3\% of total wetland area was considered jurisdictional by
rule, 11.7\% of wetland area required further evaluation through the
significant nexus test, and less than 0.1\% of wetland area was
non-jurisdictional. In contrast, the NWPR reduced the area of
jurisdictional wetlands to 78.1\%, leaving 21.9\% of New York's wetland
area non-jurisdictional by rule. The CWR has the potential to protect up
to a maximum of 99.9\% of wetland area, though the true magnitude of
protections is dependent on the site-specific evaluation of the
significant nexus test. We estimate that the NWPR decreases
jurisdictional wetland area by 11.6\% as compared to the CWR state-wide,
resulting in a loss in protection for at least 89,000 ha of wetlands in
NYS. Additional wetland losses, though unquantified in this study, are
likely, given the NWPR's elimination of the significant nexus test.

Across New York's 16 USGS HUC6 basins, we found that federal wetland
protections varied considerably in space (Figure 2). Between hydrologic
basins, CWR jurisdictional wetland area varied from a minimum of 76.5\%
(HUC 041201) to a maximum of 97.4\% (HUC 020302). NWPR jurisdictional
wetland area ranged between a minimum of 55.3\% (HUC 041201) and a
maximum of 86.6\% (HUC 020301). We also observed substantial spatial
variability in shifts in legal protections from the CWR to the NWPR
across basins. For example, the replacement of the CWR by the NWPR
resulted in a 27.5\% loss of jurisdictional wetlands area in HUC 042701,
but only a loss of 4.4\% in HUC 020401.

\textbf{3.2 Federal Wetland Protections Vary as a Function of Wetland
Size and Landscape position}

Wetlands are unevenly distributed across the landscape, both in terms of
individual wetland size and the position of wetlands in relation to
stream networks. The size-frequency relationship of wetlands tends to
follow a power-law distribution, with smaller wetlands occurring orders
of magnitude more frequently on the landscape than comparatively larger
wetlands (Van Meter \& Basu, 2015). This relationship holds for NYS,
where 73.2\% of unique wetlands are smaller than 1 ha in size (Figure
3). However, while the majority of New York wetlands are relatively
small, the largest proportion of total wetland area is concentrated
amongst a limited number of large wetlands. Although wetlands larger
than 30 ha make up only 1.1\% of NYS wetlands by number, they represent
44.2\% of total wetland area (Figure 3).

The position of wetlands in relation to the nearest jurisdictional water
also follows a skewed distribution (Figure 3). Of NYS's wetlands, 52.8\%
of unique wetlands and 84.7\% of total wetland area are located within
100 ft (30.5 m) of the stream network. We also observe that wetlands
located at greater distances from the stream network tend to be smaller
in area than those positioned near streams (Figure 4). While most of New
York's wetlands are relatively small and located across a wide range of
distances from the stream network, the majority of total wetland area is
concentrated near the stream network, contributed by large wetlands.

We observe that both the CWR and NWPR preferentially protect wetlands in
close proximity to the stream network, though this phenomenon is more
pronounced for the NWPR (Figure 4). Within 100 ft (30.5 m) of the stream
network, the CWR protects 100\% of NYS wetlands by rule, representing
over 740,000 ha of total wetland area. Of wetlands located between 100
and 4000 ft (30.5 and 1219.2 m) from streams, 14.1\% of unique wetlands
(23.4\% of total area) are afforded jurisdictional status by the CWR
while the remaining 85.9\% of unique wetlands (76.6\% of total area)
require further evaluation under the significant nexus test. With its
requirement of a surface-water connection, the NWPR considerably narrows
the extent of protected wetlands toward the stream network. In direct
comparison to the CWR, the NWPR protects only 74.4\% of wetlands (92.1\%
of total area) within 100 ft (30.5 m) of the jurisdictional stream
network and no wetlands outside of 100 ft (30.5 m). Despite these
decreases, the NWPR still protects roughly 690,000 ha of wetlands within
100 ft (30.5 m) of the stream networks.

Coupled with the distribution of wetlands on the landscape, these
geographic patterns result in distinct biases in the sizes of wetlands
conserved (Figures 4 and 5). Under both rules, larger wetlands are
considerably more likely to be classed as jurisdictional, while
comparatively smaller wetlands tend to fall into the significant nexus
or non-jurisdictional categories. Of wetlands larger than 30 ha, 99.0\%
and 96.2\% of wetland area are jurisdictional under the CWR and NWPR,
respectively. By comparison, wetlands smaller than 1 ha received
markedly less protection, with only 57.8\% and 36.9\% of wetland area
considered jurisdictional by rule under the CWR and NWPR, respectively.
With decreasing wetland size, wetlands become increasingly dependent on
the CWR significant nexus test to receive legal protection (Figure 5).
Roughly 43\% of wetlands smaller than 1 ha required the application of
the significant nexus test under the CWR, compared to 0.99\% of wetlands
larger than 30 ha. We note that this size bias has little effect on the
total area of wetlands protected, as small but numerous wetlands
contribute a relatively small proportion of wetland area.

\textbf{4.0. Discussion}

\textbf{4.1. What are the Implications of Changing Regulations for
Wetland Protection in NYS?}

The CWR and NWPR's contrasting approaches to wetland protection result
in clear disparities in the protection of wetlands. Across all
hydrologic regions of NYS, the NWPR consistently protects fewer wetlands
by both total area and number compared to the CWR (Figure 2). This
finding is in close agreement with other studies that document decreased
protections for wetlands moving from the CWR to NWPR at both state and
watershed scales (Meyer \& Robertson, 2019; Mihelcic \& Rains, 2020;
Walsh \& Ward, 2019). The consequences of the NWPR on wetland
protections are two-fold. First, the NWPR's strict requirement of a
surface-water connection between a wetland and another jurisdictional
waterway, replacing the CWR's framework of buffer distances, severely
limits the total area of wetlands protected (Figure 2). Compounding
those losses, the removal of the significant nexus test under the NWPR
eliminates potential protections for a diverse subset of wetlands
located at distance from the stream network. While the NWPR claims to
simplify wetland regulation, it does so at the expense of lost
protections for many NYS wetlands.

In NYS, we also observed considerable heterogeneity in wetland
protections across hydrologic regions (Figure 2). Although statewide
statistics of protection can be informative in the aggregate, they mask
a wider range of extreme outcomes at smaller spatial scales. Between
individual hydrologic regions of NYS, we found that the percent of
jurisdictional area protected under the CWR and NWPR varied by up to
20.9\% and 31.3\%, respectively. This result emphasizes that federal
regulations generate considerable spatial non-uniformity in wetland
protections. Indeed, our documentation of spatial inconsistencies in
protections highlights that the conservation of wetlands is a strongly
regional issue. The efficacy of wetland regulation is likely tied to the
distribution of wetlands on the landscape, which is controlled by
gradients in topography, geology, subsurface flow, and climate at
regional to continental scales (e.g., Bertassello et al., 2020). The
patterns of wetland protection in New York, a state that spans a variety
of Northeastern ecoregions, cannot be easily extrapolated to other areas
of the US with dissimilar landscape characteristics and wetland
distributions. This regional heterogeneity underscores the need for
additional analyses of wetland policy in other diverse ecoregions of the
US, furthering a more geographically comprehensive understanding of the
implications of regulation.

\textbf{4.2 Biases in Protection: Which Wetlands Do Our Regulations
Ignore?}

The regulatory approach taken by the NWPR, centered around the criteria
of surface-water connection, contracts the distribution of protected
wetlands inwards towards the stream network and exacerbates historical
trends in upland wetland loss (Van Meter \& Basu, 2015). By requiring a
connection between surface waters and wetlands, the NWPR introduces a
strong bias against small, geographically isolated features. However, as
a considerable proportion of NYS's wetland area is concentrated in large
wetlands near the stream network (Figure 2), the NWPR's spatial
constriction of regulations has an undersized impact on the total area
of wetlands protected (Figure 4). While the CWR has a similar (though
less severe) jurisdictional bias against small wetlands, the existence
of the significant nexus test may serve to protect upload wetlands,
especially as wetland size decreases (Figure 5). The elimination of the
significant nexus test by the NWPR entirely omits protections for these
smaller, distal wetlands.

Although the NWPR results in a mere 11.6\% decrease in jurisdictional
wetland area compared to the CWR, its strong bias against geographically
isolated wetlands could result in outsized impacts on water quality,
nutrient cycling, and other ecosystem services (Cohen et al., 2016;
Sullivan et al., 2019, 2020). Small, isolated wetlands cycle nutrients,
carbon, and pollutants at disproportionately high rates due to their
ratio of reactive area to storage and their long residence times (Cheng
\& Basu, 2017; Ghermandi et al., 2010; Marton et al., 2015). These
wetlands do not meet the criteria for protection under the NWPR, yet
they are undoubtedly linked to the quality of downstream waters through
hydrological and biogeochemical exchanges along slower subsurface flow
paths (USEPA, 2015; Cohen et al., 2016). The heterogeneous aquatic
habitats provided by isolated wetlands also facilitate biological
connectivity across the landscape, enabling regional species dispersal
and enhancing spatial biodiversity (Cohen et al., 2016; Scheffer et al.,
2006).

The NWPR represents a clear step towards a more homogeneous
wetlandscape. While the CWR attempts to protect wetlands spanning a wide
range of sizes and landscape positions, the NWPR takes a contrasting
regulatory approach, focusing protections on (larger) wetlands near the
stream network. These floodplain wetlands undoubtedly provide extensive
benefits such as peak flow attenuation (Ameli \& Creed, 2019). However,
concentrating protections on floodplain wetlands alone could critically
threaten the multitude of ecosystem services provided by isolated,
upland wetlands. Non-floodplain wetlands are inherently heterogeneous,
spanning broad spectrums of size, shape, landscape position,
connectivity, and hydrologic residence time (Evenson et al., 2018;
Golden et al., 2019). The cumulative landscape effects of these diverse
and often isolated wetlands are integral to watershed-scale resilience,
contributing resistance to regime change instigated by hydrological,
biogeochemical, and anthropogenic disturbances (Golden et al., 2021;
Lane et al., 2022). By specifically targeting upland wetlands, the
implementation of regulatory strategies akin to the NWPR could result in
considerable negative impacts on downstream water quality, including
increased peak discharges, sediment and nutrient loading, and
eutrophication (Lane et al., 2022; Yang et al., 2010).

\textbf{4.3. Challenges and Opportunities in Translating Federal Policy
into Quantitative Landscape Impacts}

Overall, the development of federal wetland policy is underlain by an
inherent tension between the recognized economic and environmental
benefits of wetlands and the costs of regulation (Boyle et al., 2017).
Although the preservation of a diverse suite of wetlands may ensure that
a complete set of ecosystem services is maintained, we acknowledge that
striving for policy that is clear, efficient, and interpretable is
equally desirable (Mihelcic \& Rains, 2020). Above all, regulations that
contain definitions such as WOTUS often require interpretation by
scientists and regulators, and consistent and clear guidelines can help
to reduce uncertainty and make enforcement more efficient. While
geospatial analyses such as this study can provide initial evaluations
of policy outcomes, the translation of regulations into quantitative
assessments of landscape impacts often requires more detailed and
site-specific approaches. The implementation of Clean Water Act
protections has long relied upon boots-on-the-ground assessments, and no
amount of geospatial data can substitute for case-by-case field studies.
Still, we assert that while regulatory determinations based on spatial
data may be imperfect, broad-scale geospatial evaluations of wetland
policy still provide considerable utility. Such approaches can be used
to make a significant proportion of preliminary assessments of wetland
jurisdiction, providing substantial benefits to regulators and
landowners alike. While wetland-by-wetland assessments may be more
accurate in determining the regulatory status of individual waters,
geospatial analyses are still needed to capture complex and non-uniform
regional patterns in protections across the landscape.

Despite the unique advantages provided by broad-scale assessments of
wetland policy, we also acknowledge that such approaches are limited by
imperfections inherent to all types of geospatial data. In wetland
inventories, the extent of vulnerable non-floodplain wetlands is often
insufficiently mapped due to their small size and dynamic state (Lane et
al., 2022). Similarly, existing datasets representing the stream network
at regional and broader scales are known to conservatively estimate
river network extent (Elmore et al., 2013). Likewise, the location and
extent of the stream network, which presently determines wetland
protections under the CWA, expands and contracts seasonally and from
year to year, making it difficult to map streams effectively (Godsey \&
Kirchner, 2014; Ward et al., 2018). Wetland locations and their
connectivity to adjacent waters are also uncertain and prone to
variations on a seasonal basis due to shifts in annual weather
conditions and impacts from human activity. In aggregate, these
uncertainties demonstrate that a combination of field evidence and
professional judgment is still required to evaluate the regulatory
status of a particular wetland. Regardless of these challenges,
data-driven investigations such as the one presented here are a
necessary step to ensure that we understand how the policies of today
will impact the landscapes of the future (Mihelcic \& Rains, 2020).

With yet another WOTUS revision on the horizon (USDOD and USEPA, 2021),
it is a crucial time to consider the implications of existing science
and to evaluate how changes to federal regulations will impact wetland
protections and the environment at large. While the effects of recent
WOTUS iterations have been assessed across several watersheds (Meyer \&
Robertson, 2019; Walsh \& Ward, 2019), our understanding of the
potential country-wide impacts of regulations such as the NWPR is
worryingly deficient (Sullivan et al., 2020). Our findings of
non-uniformity in the protection of wetlands across hydrologic regions,
landscape positions, and wetland sizes indicate that the impacts of
regulation are too complex to be extrapolated from studies at individual
watersheds. Current and future wetland policy must be assessed at a
national level to ensure that regulations uphold the CWA's goal of
maintaining the chemical, physical, and biological integrity of US
waters (Federal Water Pollution Control Act Amendments, 1972). By
investigating regulatory impacts at a continental scale, rather than
generalizing from local-scale case studies, policymakers can ensure that
wetlands receive equitable protections across the many diverse
ecoregions of the US.

\textbf{5.0. Conclusion}

The regulatory definition of WOTUS has been the source of a litany of
lawsuits and repeated debates over rulemaking related to federal
wetlands protection. While interpretations of environmental policy will
always require judgment on a case-by-case basis, analyses like ours
present a broad-scale assessment of the changes that will be realized on
the landscape as a function of changing federal rules. Key findings of
our study include:

\begin{itemize}
\tightlist
\item
  In comparison to the CWR, the NWPR decreases the total area and number
  of wetlands protected in New York State. State-wide, we estimate that
  the NWPR protects 11.6\% less total wetland area than the CWR, with a
  potential for greater losses in protection depending on the evaluation
  of the CWR's significant nexus test.
\item
  The impacts of regulatory change on wetland protections are highly
  variable across regions (e.g., HUC-by-HUC differences within a single
  state as shown here). As such, we discourage the extrapolation of
  watershed-scale policy outcomes to broader regions and suggest that a
  comprehensive approach is necessary to understand regulatory impacts.
\item
  Federal wetland regulation can result in a non-uniform distribution of
  protections across the landscape. With its use of a surface water
  connection as criteria for jurisdiction, the NWPR preferentially
  protects larger wetlands close to the stream network, leaving smaller
  and more geographically isolated wetlands particularly vulnerable. The
  loss of these unprotected, non-floodplain wetlands could result in a
  considerable decline in ecosystem function, given their unique
  biological and chemical functions.
\end{itemize}

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\textbf{Figure Captions:}

\textbf{Figure 1.} Distribution of 373,000 non-marine wetlands in New
York State as recorded by the National Wetland Inventory. Within each of
New York's 16 HUC6 basins, the jurisdictional status of wetlands was
assessed based on proximity to the stream network derived from the
National Hydrography Dataset. Inset displays the spatial relationship
between wetlands and the stream network within a single basin.

\textbf{Figure 2.} Percentage of wetland area guaranteed jurisdictional
status under the CWR and NWPR state-wide and within each of New York's
HUC6 basins. Values to the right of bars indicate the percent change in
jurisdictional wetland area from the CWR to the NWPR scenarios.

\textbf{Figure 3.} Relationship between wetland area and proximity to
the nearest jurisdictional water. Wetlands were grouped into bins of
areas and distances to evaluate their distribution on the landscape with
respect to both the number of unique wetlands and total wetland area.
Zero values indicate that no wetlands fell within that particular area
and distance range.

\textbf{Figure 4.} Wetland protection statuses under the CWR and NWPR as
they relate to wetland size and landscape position. Wetlands can receive
protection under the CWR by either being jurisdictional by rule
(leftmost panels) or through the application of the significant nexus
test (center panels). Under the NWPR, wetlands may only receive legal
protection if they are jurisdictional by rule (rightmost panels). The
percent of wetlands protected is calculated based on the proportion of
unique wetlands within each size-distance bin that are classified into
each regulatory category (top panels). Total area protected reflects the
sum of wetland area within each size-distance bin for a particular
regulatory category (bottom panels). NA values indicate that no wetlands
fell within that particular area and distance range.

\textbf{Figure 5.} Percentage of wetland area protected within ranges of
wetland sizes under the NWPR and the CWR. Given the uncertainty in the
regulatory status of wetlands requiring the application of the CWR's
significant nexus test, CWR protections may vary considerably, up to a
maximum jurisdictional percentage (CWR Max Jur.) equal to the sum of
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