Supplementary Material
The impact of river regulation on the biodiversity intactness of floodplain wetlands
Jan J. Kuiper1,2*, Jan H. Janse1,3, Sven Teurlincx1, Jos T.A. Verhoeven2 & Rob Alkemade3
1
Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box
50 NL-6700 AB, Wageningen, The Netherlands. 2 Ecology and Biodiversity, Institute of
Environmental Biology, Utrecht University, H.R. Kruytgebouw, Padualaan 8, 3584 CH,
Utrecht, The Netherlands. 3 PBL -Netherlands Environmental Assessment Agency, P.O. Box
303, 3720 AH Bilthoven, The Netherlands.
* Corresponding author. Email: jankuiper87@gmail.com
This document contains:
Online Resource 1 – Short description of the studies
Online Resource 2 – Variances & Categorization
Online Resource 3 – Forest plots & Funnel plots
Online Resource 4 – Linking up with GLOBIO-aquatic
1
Online Resource 1
Table S1. Short introduction of the studies that met the selection criteria, and were used for the meta-analyses.
Reference
Location
Biome
Taxon
Methods
No. sets
Mallik and
Richardson
2009
British
ColumbiaCanada
Temperate
forest
Plants
Reference in space;
same river. 3 rivers. 1
site per treatment per
river, 5 transects per
site, 14 plots per
transect.
6
(3 rivers; LR
and MSA)
Paetzold,
Yoshimura
and
Tockner
2008
Multiple
Alpine
Rivers,
Europe
Temperate
forest
Inverte
brates
Reference in space;
different rivers. 3
sites at the control
rivers, 3 sites at the
impacted rivers. 3
sampling periods in
the same year, 24
plots per site per
sampling period.
6 (three
disturbance
treatments;
LR and
MSA)
2
Type of
regulation
Dam
(hydroelectric)
Channeliza
tion and
hydropeaking
Hydrological impact
The natural regime comprises
moderate flows in the spring
resulting from snow melt. A
recession during the drier
summer months, followed by
periods of frequent high
discharge associated with storm
events in the winter. Water is
diverted away from the original
outflow, and the flow to those
receiving streams has been
regulated (stabilized) and
maintained at low levels.
The natural flow regime was
controlled by rainfall glacier
and snow melt. Hydro power
operation caused major diel
flow variations and reduced
seasonal and inter-annual flow
extremes as a result of
decreased summer and
increased winter discharge.
Channelization increased
inundation frequency.
Degree of
regulation
‘high’ and
‘medium’
Effects
‘high’ and
‘low’
Reduction in
abundance and
richness.
Inconsistent
changes in
richness and
abundance of
riparian
vegetation,
reduction in
abundance of
trees.
Table S1. Short introduction of the studies that met the selection criteria, and were used for the meta-analyses.
Reference
Location
Biome
Taxon
Methods
No. sets
Type of
regulation
Dam
(waterstorage)
Hydrological impact
Beauchamp
and
Stromberg
2008
Verde
River,
Arizona
USA
Grassland
and Steppe
Plants
1 (LR)
Shafroth,
Stromberg
and Patten
2002
Bill
Williams
River,
Arizona
USA
Hot desert
Plants
Reference in space;
same river. 3
unregulated and 4
regulated sites. 9
100m2 plots per site,
5 quadrates within
each plot. Two
sampling period per
year, 2 years in a
row.
Reference in space;
different reaches. 8
sites per river, 5 plots
per transect, sampled
two times. Sampled
during different
seasons.
Jansson et
al. 2000
Several
Rivers,
Sweden
Boreal
Forest
Plants
Reference in space;
different rivers (2
pairs). Number of
sites per river ranged
from 10 – 46, each
site encompassed a
200 m transects.
Sampling period was
spread over several
years.
1 (MSA)
Dam
(floodcontrol)
2 (2 pairs of
rivers; LR)
Dam
(hydroelectric)
3
Degree of
regulation
‘medium’
Effects
Dramatic reduction of the
magnitude of the 10-yr peak
flows. The natural flow was
controlled by frontal winter rain
and convectional monsoonal
rain in late summer and early
fall.
‘high’
The natural regime includes
large seasonal water-level
fluctuations. The annual waterlevel maximum occurs during
the spring or early summer due
to snowmelt. The maximum
flood is typically two orders of
magnitude larger than the
annual minimum discharge in
late winter. Regulation causes
the water level to be at its
lowest in spring. Also the
average discharge is reduced,
and hydro-peaking occurs.
‘high’ and
‘medium’
Flow regulation
narrowed the river
creating more
riparian habitat
and increased the
abundance of
riparian
vegetation.
In general
regulated rivers
showed lower
species richness
and reduced
abundance.
Dams are operated for water
storage and have no hydropower
capabilities or diversion
structures. Large floods still
occur due to the relative small
storage capacity of the
reservoirs. Smaller floods are
prevented.
Reduction in
abundance and
richness.
Table S1. Short introduction of the studies that met the selection criteria, and were used for the meta-analyses.
Reference
Location
Biome
Taxon
Methods
No. sets
Chauhan
and Gopal
2005
River
Yamuna,
India
Scrubland
Plants
Reference in time. 1
site, 40 plots per
survey, multiple
surveys per year.
4 (2
disturbance
classes; LR
and MSA)
Ellis,
Crawford
and Molles
2001
Rio
Grande,
New
Mexico,
USA
Grassland
and Steppe
Inverte
brates
2 (LR and
MSA)
Levee
Gergel,
Dixon and
Turner
2002
Wisonsin
River,
Wisconsin,
USA
Temperate
Forest
Plants
Reference in space;
same river. 1 site per
treatment, 30 traps
per site, sampled
multiple times per
year, during several
succeeding years.
Reference in space;
same river. 10
transects, 33 plots per
treatment.
1 (MSA)
Levee
(Flood
control)
4
Type of
regulation
Dyke
Hydrological impact
A floodplain area lying next to a
newly constructed reservoir
initially experienced increasing
depth, duration and frequency of
flooding due to seepage. Dyke
compaction however resulted in
cessation of seepage and the site
dried out.
The natural regime includes
large seasonal water-level
fluctuations. The annual waterlevel maximum occurs during
late summer. The levee
prevented that any flooding
could occur.
Upstream dams cause
daily fluctuations. Average
water level is highest in spring,
when the discharge is three
times higher than in autumn.
Small floods occur every two
years. The mean number of
floods and days inundated were
all zero (significantly lower) in
areas outside of levees.
Degree of
regulation
‘high’ and
‘low’
Effects
‘high’
No effect on
taxonomic
richness, some
species showed
reduced
abundance.
‘high’
Changes in
species
abundance.
Reduced richness
and changes in
abundance.
Table S1. Short introduction of the studies that met the selection criteria, and were used for the meta-analyses.
Reference
Location
Biome
Taxon
Methods
No. sets
Franklin et
al. 2009
Several
rivers,
Tennesee,
USA
Temperate
Forest
Plants
Reference in space;
different rivers. 2
rivers per treatment.
+/- 13 plots per river
per treatment.
4 (2
disturbance
classes; LR
and MSA)
Gubiani et
al. 2007
Upper
Parana
River,
Brazil
Tropical
forest
Fish
1 (MSA)
Dam
(hydroelectric
and flood
control)
Falck,
Wilson and
Andersen
2003
Green and
Yampa
river,
Colorado,
USA
Grassland
and Steppe
Mamm
als
Reference in time; 6
lagoons sampled
before impact, 7
lagoons sampled after
impact. Location and
size of the lagoons
varied between study
periods.
Reference in space
(same river/different
river). 1 site per
treatment, sampled at
different distances
from the river during
different periods with
respect to the flood
pulse, in two
succeeding years.
Trap-nights ranged
from 19 to 1402 for
location and period.
4 (2
disturbance
classes; LR
and MSA)
Dam
(hydroelectric)
5
Type of
regulation
Levee
Hydrological impact
Naturally, floods occur in most
years during winter and spring
and occasionally during
summer. In channelized and
leveed systems, the floodplain is
completely cut off from the
channel. Without levees,
flooding remains potentially
important for channelized
reaches as high water table
levels are then maintained.
An intense flood pulse caused
regularly flooding of flood plain
lagoons. No flood pulse
occurred after damming. Winter
water levels decreased, summer
water level increased. No
migration was possible due to
reduced connectivity.
The early summer flow peak
disappeared; winter discharge
was increased.
Degree of
regulation
‘high’ and
‘low’
Effects
‘medium’
Reduced
abundance
‘high’ and
‘medium’
More species
captured in the
most regulated
site. Differences
in species
abundance.
Small reduction in
richness and
differences in
species
abundances.
Table S1. Short introduction of the studies that met the selection criteria, and were used for the meta-analyses.
Reference
Location
Biome
Taxon
Methods
No. sets
Hyslop
1988
Rima
River,
Nigeria
Scrubland
Fish
2 (LR and
MSA)
Jenkins and
Boulton
2007
Teryaweyn
ya
floodplain
lakes
system,
Australia
South Fork
Repuclican
River,
Colorado
USA
Hot desert
Inverte
brates
Reference in time.
Approx. 100 days of
fishing per year. 3
years in a row before
completion of the
dam, 1 year after
completion.
Reference in space
(different lakes). 3
lakes per treatment.
2x5 samples per lake.
Grassland
and Steppe
Plants
Multiple
floodplain
lakes,
Australia
Scrubland
Birds
Katz,
Friedman
and Beatty
2005
Kingsford,
Jenkins and
Porter 2004
Type of
regulation
Dam
(flood
control and
irrigation)
Hydrological impact
1(LR)
Dams
(water
withdrawal)
Reference in space
(same river). Three
sites per treatment. 1
transect per site, 5
plots per transect.
1 (MSA)
Dam
(flood
control and
recreation)
Reference in space
(different floodplain
lakes). 3 floodplain
systems per
treatment, 2 lakes per
floodplain system.
Annual aerial surveys
over a period of 19
years
2 (LR and
MSA)
Water
table
regulation
Without river regulation, time
between medium-sized floods
resulting in flood plain
inundation was approx. 6 years,
after regulation this became 20
years.
Above the dam, there is high
discharge in spring and summer.
Peak flows are driven by
storms. Both the peak and mean
discharge were reduced, leading
to channel narrowing.
Regulated floodplain lakes
(reservoirs) had stable water
levels. Unregulated lakes dried
out regularly. The mean
coefficient of variation for
flooded area was about half as
much on regulated as on
unregulated lakes.
6
Summer flood pulse was
reduced and delayed; the
floodplain was only marginally
flooded.
Degree of
regulation
‘high’
Effects
‘high’
Reduced richness.
‘high’
Reduced
abundance
‘high’
Reduced richness
and reduced
abundance.
Reduced richness
and reduced
abundance.
Table S1. Short introduction of the studies that met the selection criteria, and were used for the meta-analyses.
Reference
Location
Biome
Taxon
Methods
No. sets
Vanhara
1991
Dyje and
Morava
Rivers,
former
Checkslovakia
Temperate
forest
Inverte
brates
2 (2 types of
hydrologic
alteration;
LR)
Uowolo,
Binkley and
Adair 2005
Green
River &
Yampa
River,
Colorado
USA
Nederrijn,
Waal/Ijssel
lowland
rivers, The
Netherland
s
Grassland
and Steppe
Plants
Temperate
forest
Plants
St.
Lawrence
River, New
York, USA
Temperate
mixed
forest
Mamm
als
Reference in time.
Sampling occurred 2
or 3 times per month
for period of resp. 9
and 11 years. For the
reference location
existing data on
species richness was
used.
Reference in space
(different river). 20
sites at the reference
river an 16 sites at the
impacted river. One
1000m2 plot per site.
Spatial (different
river branches). 66
lakes at the reference
river branches, 34
lakes at the impacted
reach. 4- 31 plots per
river. For the
abundance another
115 lakes were
sampled in total.
Spatial (experimental
site). 5 year field
surveys.
Van Geest
et al. 2005
Toner,
Farrel and
Mead 2010
Type of
regulation
Dam
(flood
control);
complete
inundation
/drying.
Hydrological impact
1 (LR)
Dam
(hydroelectric)
2 (LR,
MSA)
Weirs
1 (MSA)
Water
table
regulation/
experiment
al flooding
7
Degree of
regulation
‘high’ and
‘high’
Effects
The early summer flow peak
disappeared; winter discharge
was increased.
‘high’
Reduced richness
The natural flow varies resulting
in a difference in water levels of
up to 8 m. The highest flows
occur in winter and the lowest
in late summer and early
autumn. During the growing
season, periods of extreme low
water levels occur. Water-level
fluctuations are reduced
preventing drawdown.
High water levels during winter
months were replaced by a fall
drawdown; a management
action to accommodate winter
storage.
‘medium’
Reduced richness
and change in
species
abundance.
‘medium’
Reduced
abundance
The floodplain forest used to be
flooded each year, even several
times per year. After regulation,
maximum groundwater level
dropped by an average of 90
cm, and regular floods were
prevented.
Reduced richness
and reduction in
abundance of
original species
Table S1. Short introduction of the studies that met the selection criteria, and were used for the meta-analyses.
Reference
Location
Biome
Taxon
Methods
No. sets
Type of
regulation
Experimen
tal
flooding
Hydrological impact
Robertson,
Bacon and
Heagney
2001
Gulpa
Island State
Forest,
Murray
river
Australia
Scrubland
Plants
3 (3
disturbance
classes; LR)
Quinn et al.
2005
Kihansi
Gorge,
Tanzania
Scrubland
Plants
Reference in space
(same river). 6
replicas per
treatment, divided
over shallow and
deep regions of the
wetlands, sampled
two years in a row.
Some treatments had
fewer replicas
Reference in time. 40
1m2 plots, sampled
once per treatment.
2 (LR,
MSA)
Dam
(hydroelectric)
1 (LR)
Dam
(waterstorage)
This is a spray maintained
wetland. River regulation
caused a marked reduction of
the average natural flow and dry
season flow, causing loss of
spray that maintains the wetland
habitat
High flows in the Verde
typically occur in early spring
and are driven by winter pacific
frontal storms and by snowmelt.
Winter–spring floods occur
about once every 5–10 years.
Smaller flood flows, of the
order of the 1.5-year return
interval. There was a nearly
50% decrease in overbank
flooding frequency.
Beauchamp
Stromberg
and Stutz,
2007
Verde
River,
Arizona
USA
Grassland
and Steppe
Plants
Reference in space
(same river). 3
control sites with 27
100m2 plots, and 4
regulated sites with
34 100m2 plots.
8
The natural flood regime for
these forests was flooding in
spring. Since river damming,
small and medium floods are
less frequent in spring and small
floods are more frequent in
summer
Degree of
regulation
‘low’,
‘medium’
and ‘high’
Effects
‘high’
Small reduction in
species richness,
changes in species
abundance (mixed
effects)
‘medium’
Reduction in
abundance and
richness.
Reduced richness
Table S1. Short introduction of the studies that met the selection criteria, and were used for the meta-analyses.
Reference
Location
Biome
Taxon
Methods
No. sets
Nilsson et
al. 1991
Vindel
River and
Ume River,
Sweden
Boreal
Forest
Plants
Reference in space
(different river). 25
sites per river, each
site encompassed a
200m transect.
2 (LR and
MSA)
Lovell,
Gibson and
Heschel
2009
Arkansas
river Co
USA
Grassland
and steppe
Plants
Reference in space
(same river). One site
per treatment per
location, two 150m2
plots per site, two
transects per plot.
2 (2
locations;
MSA)
9
Type of
regulation
Dam
(hydroelectric)
Dams
(flood
control and
water
storage)
Hydrological impact
The natural flow regime
includes spring flooding and a
subsequent lowering of the
water level during the summer
and winter, with some minor
increases during the fall. In the
major water-storage reservoirs,
water level is at its lowest in
spring and is raised during
summer to reach its highest
storage level in summer. There
was reduced variation in the
discharge. Mean annual
discharge did not differ, neither
did the width and height of the
river margin.
Flow rate was similar above and
below the Pueblo Dam sites,
though small flooding events
were relatively more severe at
sites above the Pueblo Dam.
Flooding was greater in both
flow rate and flood height above
the John Martin Dam than
below it.
Degree of
regulation
‘medium’
Effects
‘medium’
Changes in
species abundance
Reduction in
abundance and
richness.
Table S1. Short introduction of the studies that met the selection criteria, and were used for the meta-analyses.
Reference
Location
Biome
Taxon
Methods
No. sets
Merritt and
Poff 2010
Several
locations in
SW USA
Grassland
and steppe
Plants
2 (2
disturbance
classes;
MSA)
Nilsson and
Jansson
1995
Several
Rivers in
Sweden
Boreal
Forest
Plants
Reference in space
(different rivers). 64
reaches on 13 rivers.
One 200 m transect
per reach parallel to
the river. 200 1m
wide belts were
established
perpendicular to the
transects across the
whole floodplain
Reference in space
(different rivers). 10
sites per river, each
site encompassed a
200m transect.
3 (3 sets of
rivers, LR)
10
Type of
regulation
Multiple
types
Hydrological impact
Dam
(hydroelectric)
The natural regime includes
large seasonal water-level
fluctuations. The annual
maximum occurs during the
spring/early summer due to
snowmelt. The regulation of
rivers has implied that riparian
corridors have been widened or
narrowed and exposed to
modified or artificial water-level
fluctuations. The water level in
the impoundments is rather
stable, whereas in the dam-todam stretches the flow is still
rather variable.
The index of flow modification
was used to compare pre- and
post-impact change in eight
relevant flow attributes. IFM
levels ranged from 0.05 to 0.99.
(0.34 average, 0.23 std). The
rivers were grouped into two
categories.
Degree of
regulation
‘medium ‘
and ‘low’
Effects
‘high’,
‘medium’
and
‘medium ‘
Reduction in
abundance and
richness.
Changes in
species abundance
Table S1. Short introduction of the studies that met the selection criteria, and were used for the meta-analyses.
Reference
Location
Biome
Taxon
Methods
No. sets
Stromberg
et al. 2007 a
San Pedro
River, Gila
River,
Arizona
USA
Scrubland
Plants
Spatial (different
reaches). 6 to 10 sites
per reach.
1 (MSA)
Stromberg
et al. 2007 b
Multiple
reaches SW
USA
Scrubland
Plants
Spatial (different
river). 9 free flowing,
5 regulated perennial
reaches. 2 to 10
transects per reach.
Several quadrates per
transect.
1 (MSA)
11
Type of
regulation
Dam and
water
abstraction
Multiple
types
Hydrological impact
Flood patterns are nonstationary, reflecting the highly
variable climate. The total flow
volume is not altered, but there
is a decreased average peak
flow rate, flood frequency, and
variability, and shifted the
timing of flow maxima
and minima. Small floods are
captured in the reservoirs, large
floods may still occur.
Reductions in flood frequency,
shifts in flood timing and abrupt
decline of flood waters, together
with changes in river
geomorphology. Not specified
per river.
Degree of
regulation
‘high’
Effects
‘medium’
Changes in
species abundance
Changes in
species abundance
Beauchamp, V.B. & Stromberg, J.C. (2008). Changes to herbaceous plant communities on a
regulated desert river. River Research and Applications, 24, 754-770.
Beauchamp, V.B., Stromberg, J.C. & Stutz, J.C. (2007). Flow regulation has minimal
influence on mycorrhizal fungi of a semi-arid floodplain ecosystem despite changes in
hydrology, soils, and vegetation. Journal of Arid Environments, 68, 188-205.
Chauhan, M. & Gopal, B. (2005). Vegetation structure and dynamics of a floodplain wetland
along a subtropical regulated river. River Research and applications, 21, 513-534.
Ellis, L.M., Crawford, C.S. & Molles Jr, M.C. (2001). Influence of annual flooding on
terrestrial arthropod assemblages of a Rio Grande riparian forest. Regulated Rivers:
Research & Management, 17, 1-20.
Falck, M.J., Wilson, K.R. & Andersen, D.C. (2003). Small mammals within riparian habitats
of a regulated and unregulated arid land river. Western North American Naturalist, 63,
35-42.
Franklin, S.B., Kupfer, J.A., Pezeshki, S.R., Gentry, R. & Smith, R.D. (2009). Complex
effects of channelization and levee construction on western Tennessee floodplain forest
function. Wetlands, 29, 451-464.
Gergel, S.E., Dixon, M.D. & Turner, M.G. (2002). Consequences of human-altered floods:
Levees, floods, and floodplain forests along the Wisconsin river. Ecological
Applications, 12, 1755-1770.
Gubiani, É.A., Gomes, L.C., Agostinho, A.A. & Okada, E.K. (2007). Persistence of fish
populations in the upper Paraná river: Effects of water regulation by dams. Ecology of
Freshwater Fish, 16, 191-197.
Hyslop, E.J. (1988). A comparison of the composition of the juvenile fish catch from the
Sokoto–Rima floodplain, Nigeria in years preceding and immediately after upstream
dam completion. Journal of fish biology, 32, 895-899.
12
Jansson, R., Nilsson, C., Dynesius, M. & Andersson, E. (2000). Effects of river regulation on
river-margin vegetation: A comparison of eight boreal rivers. Ecological Applications,
10, 203-224.
Jenkins, K.M. & Boulton, A.J. (2007). Detecting impacts and setting restoration targets in
arid‐zone rivers: Aquatic micro‐invertebrate responses to reduced floodplain
inundation. Journal of Applied Ecology, 44, 823-832.
Katz, G.L., Friedman, J.M. & Beatty, S.W. (2005). Delayed effects of flood control on a
flood-dependent riparian forest. Ecological Applications, 15, 1019-1035.
Kingsford, R.T., Jenkins, K.M. & Porter, J.L. (2004). Imposed hydrological stability on lakes
in arid australia and effects on waterbirds. Ecology, 85, 2478-2492.
Lovell, J.T., Gibson, J. & Heschel, M.S. (2009). Disturbance regime mediates riparian forest
dynamics and physiological performance, Arkansas river, CO. The American Midland
Naturalist, 162, 289-304.
Mallik, A.U. & Richardson, J.S. (2009). Riparian vegetation change in upstream and
downstream reaches of three temperate rivers dammed for hydroelectric generation in
British Columbia, Canada. Ecological Engineering, 35, 810-819.
Merritt, D.M. & Poff, N.L.R. (2010). Shifting dominance of riparian Populus and Tamarix
along gradients of flow alteration in western North American rivers. Ecological
Applications, 20, 135-152.
Nilsson, C., Ekblad, A., Gardfjell, M. & Carlberg, B. (1991). Long-term effects of river
regulation on river margin vegetation. Journal of Applied Ecology, 963-987.
Nilsson, C. & Jansson, R. (1995). Floristic differences between riparian corridors of regulated
and free‐flowing boreal rivers. Regulated Rivers: Research & Management, 11, 5566.
13
Paetzold, A., Yoshimura, C. & Tockner, K. (2008). Riparian arthropod responses to flow
regulation and river channelization. Journal of Applied Ecology, 45, 894-903.
Quinn, C.H., Ndangalasi, H.J., Gerstle, J. & Lovett, J.C. (2005). Effect of the lower kihansi
hydropower project and post-project mitigation measures on wetland vegetation in
Kihansi Gorge, Tanzania. Biodiversity and Conservation, 14, 297-308.
Robertson, A.I., Bacon, P. & Heagney, G. (2001). The responses of floodplain primary
production to flood frequency and timing. Journal of Applied Ecology, 38, 126-136.
Shafroth, P.B., Stromberg, J.C. & Patten, D.T. (2002). Riparian vegetation response to altered
disturbance and stress regimes. Ecological Applications, 12, 107-123.
Stromberg, J.C., Beauchamp, V.B., Dixon, M.D., Lite, S.J. & Paradzick, C. (2007).
Importance of low-flow and high-flow characteristics to restoration of riparian
vegetation along rivers in arid south-western united states. Freshwater Biology, 52,
651.
Stromberg, J.C., Lite, S.J., Marler, R., Paradzick, C., Shafroth, P.B., Shorrock, D. et al.
(2007). Altered stream-flow regimes and invasive plant species: The tamarix case.
Global Ecology and Biogeography, 16, 381-393.
Toner, J., Farrell, J.M. & Mead, J.V. (2010). Muskrat abundance responses to water level
regulation within freshwater coastal wetlands. Wetlands, 30, 211-219.
Uowolo, A.L., Binkley, D. & Carol Adair, E. (2005). Plant diversity in riparian forests in
northwest colorado: Effects of time and river regulation. Forest Ecology and
Management, 218, 107-114.
Van Geest, G.J., Coops, H., Roijackers, R.M.M., Buijse, A.D. & Scheffer, M. (2005).
Succession of aquatic vegetation driven by reduced water‐level fluctuations in
floodplain lakes. Journal of Applied Ecology, 42, 251-260.
14
Vaňhara, J. (1991). A floodplain forest mosquito community after man‐made moisture
changes (culicidae, diptera). Regulated Rivers: Research & Management, 6, 341-348.
15
Online Resource 2
Variances. Following Benitez-Lopez et al. 2010, the variance of the MSA value for each
dataset was estimated by calculating the variance of the external error (eq. 1), or the internal
error (2), which are both forms of the variance of a sample mean (Mood et al. 1973). Taking a
conservative approach, the larger of the two variances was used in the meta-analysis
(DerSimonian and Laird, 1986). The variances were calculated as:
2 
ext

2
int
 (MSA
s
 Ris )
2
i
(1)
N s ( N s  1)


2
Ris
(2)
N s2
Where σ2Ris is the individual variance for each ratio, which is a first-order approximation of
the variance of a ratio of two random variables, calculated using the Delta Method (3)
(Oehlert, 1992; Winzer, 2000).

2
Ris
A2
 isd
2
Aisc
 A2
 A2isc 2    Aisx   Aisp 
isd
 2  2 

Aisc
Aisx  Aisp 
 Aisd
(3)
In this equation σ2Aisd and σ2Aisc are the sampling variances of Aisd and Aisc, respectively, and ρ
their correlation coefficient. We assume Aisx and Aisp to be independent and, therefore, the
correlation coefficient ρ to be zero. In some studies no information was provided on sample
variances, in those cases we calculated variances assuming the data showed a Poisson
distribution whereby σ2 = µ (Sokal & Rohlf 1981).
2
 1
Aisd
1 

(4)

2 
Aisc  Aisd Aisc 
Finally, a continuity correction factor (k=0.05) was added to the numerator and denominator
Thus: σ2Aisd =Aisd, σ2Aisc =Aisc, and  R2is 
of the ratio of each species (also for those with densities larger than zero), resulting in slightly
higher variance estimates (Cox, 1970; Sweeting et al. 2004).
16
Categorization. Hydrological alterations were categorized into three subclasses on an ordinal
scale (low, medium high) to formalize the degree of alteration. When provided, formal indices
of hydrological alteration were used to subdivide the cases over the three categories:
Disturbance class
Low
Medium
High
Index flow modification (IFM)
< 0.33
0.33-0.66
> 0.66
Amended Annual Proportional Flow Deviation
< 1.0
1.0 – 3.0
> 3.0
(AAPFD)
When hydrographs were presented we were able to calculate the AAPFD (5) (Ladson &
White, 1999):
1
𝐴𝐴𝑃𝐹𝐷 =
𝑄𝑖 −𝑄𝑖0 2 2
[∑12
(
) ]
𝑖=1
̅̅̅̅̅
𝑄
(5)
𝑖0
In the formula, Q1 stands for adjusted discharge of the ith month. Qi0 stands for the natural
runoff of the ith month and Ǭi0 for the average of natural runoff.
In the remaining cases we considered the proportional change of the primary hydrological
components that were presented, with reference to the qualitative descriptions that were given
by the authors to divide the cases over the disturbance classes.
Disturbance class
Low
Medium
High
Proportional change (%)
< 0.33
0.33-0.66
> 0.66
One reviewer assessed the degree hydrological disturbance, with reference to a second
reviewer in cases of uncertainty.
17
References cited
Benítez-López, A., Alkemade, R. & Verweij, P.A. (2010). The impacts of roads and other
infrastructure on mammal and bird populations: A meta-analysis. Biological
Conservation, 143, 1307-1316.
Cox, D.R. (1970). The analysis of binary data. Methuen & Co Ltd, London, UK.
DerSimonian, R. & Laird, N. (1986). Meta-analysis in clinical trials. Controlled clinical trials,
7, 177-188.
Ladson, A.R., White, L.J., Doolan, J.A., Finlayson, B.L., Hart, B.T., Lake, P.S. et al. (1999).
Development and testing of an index of stream condition for waterway management in
Australia. Freshwater Biology, 41, 453-468.
Mood A.M., Graybill F.A., Boes D.C. (1973). Introduction and Theory of Statistics
(McGrawHill, Auckland), 3rd Ed.
Oehlert, G.W. (1992). A note on the delta method. American Statistician, 27-29.
Sokal, R.R. & Rohlf, F.J. (1981). Biometry: The principles and practice of statistics in
biological research. W.H. Freeman, New York, USA.
Sweeting, M.J., Sutton, A.J. & Lambert, P.C. (2004). What to add to nothing? use and
avoidance of continuity corrections in meta-analysis of sparse data. Statistics in
medicine, 23, 1351-1375.
Winzer, P.J. (2000). Accuracy of error propagation exemplified with ratios of random
variables. Review of Scientific Instruments, 71, 1447-1454.
18
Online Resource 3
Fig. S1. Forest plot for the all-encompassing meta-analysis with MSA as the metric of effect
size. The dashed vertical line represents the line of no effect (1) and the diamond indicates the
pooled effect. Error bars are the 95% confidence intervals.
19
Fig. S2. Forest plot for the all-encompassing meta-analysis with the LR as the metric of effect
size. The dashed vertical line represents the line of no effect (0) and the diamond indicates the
pooled effect. Error bars are the 95% confidence intervals.
20
Fig. S3. Funnel plot for the all-encompassing meta-analysis with MSA as the metric for effect
size. The study outcome is plotted as a function of the corresponding standard error to assess
publication bias. The solid line presents the pooled effect.
21
Fig. S3. Funnel plot for the all-encompassing meta-analysis with the LR as the metric of
effect size. The study outcome is plotted as a function of the corresponding standard error to
assess publication bias. The solid line presents the pooled effect.
22
Online Resource 4
Linking up with GLOBIO-aquatic.
GLOBIO-aquatic is a modeling framework to calculate the impact of environmental drivers
on biodiversity for present and future on a global scale. GLOBIO-aquatic is built on
empirically based cause effect relationships between environmental drivers and biodiversity
impacts, and uses spatial information on environmental drivers as input (Alkemade et al.
2009). Here we provide an example of how the results of the meta-analysis presented in this
study can be cautiously included into GLOBIO-aquatic. For input we used the water module
of the global vegetation model LPJmL (Biemans et al. 2011) to calculate the ‘amended annual
proportional flow deviation’ (AAPFD) for the year 2000. The discharge is based on a water
balance per pixel, including precipitation, evaporation, snowmelt and water abstraction as
well as the presence and management of dams and reservoirs (Biemans et al. 2011). The
AAPFD is a measure that gives the deviation between natural and impacted flow pattern
(Ladson & White, 1999). For each grid cell that includes flood-dependent wetland area (based
on the Global Lakes and Wetlands Database map) (Lehner & Doll, 2004) the continuous
AAPFD output was scaled to three ordinal disturbance classes (Online Resource 2) and linked
to the MSA values that resulted from the subgroup meta-analysis (Fig. S5). Accordingly, the
effect of hydrological alteration on the MSA can be studied in concert with impacts of other
environmental drivers represented in the GLOBIO-aquatic framework, and used for scenario
analysis (see www.globio.info for details on GLOBIO and its applications).
23
Figure S5. Spatial representation of the estimated impact of river regulation (AAPFD) on the
biodiversity intactness (MSA) in flood-dependent wetlands on a global scale (resolution
0.5°x0.5°).
Literature Cited
Alkemade, R., van Oorschot, M., Miles, L., Nellemann, C., Bakkenes, M. & Ten Brink, B.
(2009). GLOBIO3: A framework to investigate options for reducing global terrestrial
biodiversity loss. Ecosystems, 12, 374-390.
Biemans, H., Haddeland, I., Kabat, P., Ludwig, F., Hutjes, R., Heinke, J. et al. (2011). Impact
of reservoirs on river discharge and irrigation water supply during the 20th century.
Water Resources Research, 47.
Ladson, A.R., White, L.J., Doolan, J.A., Finlayson, B.L., Hart, B.T., Lake, P.S. et al. (1999).
Development and testing of an index of stream condition for waterway management in
Australia. Freshwater Biology, 41, 453-468.
Lehner B., & Doll, P., (2004). Development and validation of a global database of lakes,
reservoirs and wetlands. Journal of Hydrology, 296, 1-22.
24