ArticlePDF Available

Global Threats to Human Water Security and River Biodiversity


Abstract and Figures

Protecting the world’s freshwater resources requires diagnosing threats over a broad range of scales, from global to local. Here we present the first worldwide synthesis to jointly consider human and biodiversity perspectives on water security using a spatial framework that quantifies multiple stressors and accounts for downstream impacts. We find that nearly 80% of the world’s population is exposed to high levels of threat to water security. Massive investment in water technology enables rich nations to offset high stressor levels without remedying their underlying causes, whereas less wealthy nations remain vulnerable. A similar lack of precautionary investment jeopardizes biodiversity, with habitats associated with 65% of continental discharge classified as moderately to highly threatened. The cumulative threat framework offers a tool for prioritizing policy and management responses to this crisis, and underscores the necessity of limiting threats at their source instead of through costly remediation of symptoms in order to assure global water security for both humans and freshwater biodiversity.
Content may be subject to copyright.
ARTICLE doi:10.1038/nature09440
Global threats to human water security
and river biodiversity
C. J. Vo
*, P. B. McIntyre
*{, M. O. Gessner
, D. Dudgeon
, A. Prusevich
, P. Green
, S. Glidden
, S. E. Bunn
C. A. Sullivan
, C. Reidy Liermann
& P. M. Davies
Protecting the world’s freshwater resources requires diagnosing threats overa broad range of scales, from global to local.
Here we present the first worldwide synthesis to jointly consider human and biodiversity perspectives on water security
using a spatial framework that quantifies multiple stressors and accounts for downstream impacts. We find that nearly
80% of the world’s population is exposed to high levels of threat to water security. Massive investment in water
technology enables rich nations to offset high stressor levels without remedying their underlying causes, whereas
less wealthy nations remain vulnerable. A similar lack of precautionary investment jeopardizes biodiversity, with
habitats associated with 65% of continental discharge classified as moderately to highly threatened. The cumulative
threat framework offers a tool for prioritizing policy and management responses to this crisis, and underscores the
necessity of limiting threats at their source instead of through costly remediation of symptoms in order to assure global
water security for both humans and freshwater biodiversity.
Water is widely regarded as the most essential of natural resources, yet
freshwater systems are directly threatened by human activities
stand to be further affected by anthropogenic climate change
systems are transformed through widespread land cover change, urb-
anization, industrialization and engineering schemes like reservoirs,
irrigation and interbasin transfers that maximize human access to
. The benefits of water provision to economic productivity
often accompanied by impairment to ecosystems and biodiversity, with
potentially serious but unquantified costs
. Devising interventions to
reverse these trends, including conventions
and scientific assessments
to protect aquatic biodiversity and ensure the sustainability of water
delivery systems
, requires frameworks to diagnose the primary threats
to water security at a range of spatial scales from local to global.
Water issues feature prominently in assessments of economic
, ecosystem services
, and their combination
However, worldwide assessments of water resources
rely heavily on
fragmented data often expressed as country-level statistics, seriously
limiting efforts to prioritize their protection and rehabilitation
High-resolution spatial analyses have taken understanding of the
human impact on the world’s oceans
and the human footprint on
to a new level, but have yet to be applied to the formal assessment
process for freshwater resources
despite a recognized need
The success of integrated water management strategies depends on
striking a balance between human resource use and ecosystem pro-
. To test the degree to which this objective has been
advanced globally, and to assess its potential value in the future,
requires systematic accounting. An important first step is to develop
a spatial picture of contemporary incident threats to human water
security and biodiversity, where the term ‘incident’ refers to exposure
to a diverse array of stressors at a given location. Many stressors
threaten human water security and biodiversity through similar
pathways, as for pollution, but they also influence water systems in
distinct ways. Reservoirs, for example, convey few negative effects on
human water supply, but substantially impact on aquatic biodiversity
by impeding the movement of organisms, changing flow regimes and
altering habitat. Similarly, non-native species threaten biodiversity
but are typically inconsequential to human water security.
Here we report the results of a global-scale analysisof threats to fresh
water that, for the first time, considers human water security and
biodiversity perspectives simultaneously within a spatial accounting
framework. Our focus is on rivers, which serve as the chief source of
renewable water supply for humans and freshwater ecosystems
use river networks to redistribute the distinctive impacts of stressors on
human water security and biodiversity along a continuum from head-
waters to ocean, capturing spatial legacy effects ignored by earlier
studies. Our framework incorporates all major classes of anthro-
pogenic drivers of stress and enables an assessment of their aggregate
impact under often divergent value systems for biodiversity and
human water security. Enhancing the spatial resolution by orders-of-
magnitude over previous studies (using 309latitude/longitude grids)
allows us to more rigorously test previous assertions on the state of the
world’s rivers and to identify key sources of threat at sub-national
spatial scales that are useful for environmental management. Finally,
we make the first spatial assessment of the benefits accrued from tech-
nological investments aimedat reducing threats to human water secur-
ity, revealing previously unrecognized, global-scale consequences of
local water management practices that are used extensively worldwide.
Global patterns of incident threat
Using a global geospatial framework
, we merged a broad suite of
individual stressors to produce two cumulative incident threat indices,
one for human water security and one for biodiversity. The resulting
The Environmental CrossRoads Initiative, City University of New York, The City College of New York, New York, New York 10035, USA.
School of Natural Resources and Environment, University of Michigan,
Ann Arbor, Michigan 48109, USA.
Department of Aquatic Ecology, Eawag: Swiss Federal Institute of Aquatic Science and Technology, and Institute ofIntegrative Biology (IBZ), ETH Zurich,8600 Du
Switzerland and Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), 16775 Stechlin, Germany.
Division of Ecology and Biodiversity, School of Biological Sciences, The University of Hong
Kong, Hong Kong SAR, China.
Water Systems Analysis Group, University of New Hampshire, Durham, New Hampshire 03824, USA.
Australian Rivers Institute, Griffith University, Nathan, Queensland
4111, Australia.
School of Environmental Science and Management, Southern Cross University, New South Wales 2480, Australia.
School of Aquatic and Fishery Sciences, University of Washington,
Seattle, Washington 98195, USA.
Centre of Excellence in Natural Resource Management, The University of Western Australia, Albany 6330, Australia. {Present address: Center for Limnology, University of
Wisconsin, Madison, Wisconsin 53706, USA. *These authors contributed equally to this work.
30 SEPTEMBER 2010 | VOL 467 | NATURE | 555
Macmillan Publishers Limited. All rights reserved
maps reflect the central role of hydrology in spatially configuring
environmental impacts, with local stressor loads routed downstream
through digital river networks
and adjusted for new sources and
dilution (Supplementary Methods and Supplementary Fig. 1).
Similar to an approach used for marine systems
, multiple stressors
were combined using relative weights to derive cumulative threat
indices. Stressors were expressed as 23 geospatial drivers organized
under four themes (catchment disturbance, pollution, water resource
development and biotic factors). Expert assessment of stressor impacts
on human water security and biodiversity produced two distinct
weighting sets, which in turn yielded separate maps of incident threat
reflecting each perspective.
We find that nearly 80% (4.8 billion) of the world’s population (for
2000) lives in areas where either incident human water security or
biodiversity threat exceeds the 75th percentile. Regions of intensive
agriculture and dense settlement show high incident threat (Fig. 1), as
exemplified by much of the United States, virtually all of Europe
(excluding Scandinavia and northern Russia), and large portions of
central Asia, the Middle East, the Indian subcontinent and eastern
China. Smaller contiguous areas of high incident threat appear in
central Mexico, Cuba, North Africa, Nigeria, South Africa, Korea
and Japan. The impact of water scarcity accentuates threat to dry-
lands, as is apparent in the desert belt transition zones across all
continents (for example, Argentina, Sahel, Central Asia, Australian
Murray–Darling basin).
Spatial differentiation of incident threat also arises from the inter-
action of multiple factors. China’s arid western provinces would be
expected to show high threat due to minimal dilution potential, but
sparse population and limited economic activity combine to keep
indices low. In contrast, heavily populated and developed eastern
China shows substantially higher threat, despite greater rainfall and
dilution capacity, especially within the Yangtze basin. Other large
rivers are incapable of fully attenuating the impacts of concentrated
development. Over 30 of the 47 largest rivers, which collectively dis-
charge half of global runoff to the oceans, show at least moderate
threat levels (.0.5) at river mouth, with eight rivers (for human water
security) and fourteen (for biodiversity) showing very high threat
A strikingly small fraction of the world’s rivers remain unaffected
by humans. Remote areas of the world including the high north
(Siberia, Canada, Alaska) and unsettled parts of the tropical zone
(Amazonia, northern Australia) show the lowest threat levels.
Across remote areas (Fig. 1), incident threat arises largely from
trans-boundary atmospheric pollution. A mere 0.16% of the Earth’s
area experiences low scores for every contributing stressor (that is,
lowest decile globally).
Upstream–downstream transects of incident threat yield signatures
of human water security or biodiversity conditions unique to each
river that arise from the action of hydrology and networked flow paths
(Fig. 2). Such transects highlight the diversity of stressors in river
No appreciable ow
No appreciable ow
0.2 0.6
0.4 0.80
Incident human water
security threat
0.2 0.6
0.4 0.80
Incident biodiversity
Figure 1
Global geography of incident threat to human water security and
biodiversity. The maps demonstrate pandemic impacts on both human water
security and biodiversity and are highly coherent, although not identical
(biodiversity threat 50.964 3human water security threat 10.018; r50.97,
P,0.001). Spatial correlations among input drivers (stressors) varied, but were
generally moderate (mean
50.34; n5253 comparisons). Regional maps
exemplify main classes of human water security threat (see main text and
Supplementary Fig. 4). Spatial patterns proved robust in a varietyof sensitivity
tests (Supplementary Methods and Supplementary Discussion). Threat indices
are relative and normalized over discharging landmass.
556 | NATURE | VOL 467 | 30 SEPTEMBER 2010
Macmillan Publishers Limited. All rights reserved
systems, combining the accumulation of diffuse non-point source
pollutants with dilution by less impacted tributaries, often punctuated
by point sources from large urbanized areas. Levels of threat often
grow in the downstream direction (for example, the Huang He and
Nile rivers), indicating the accumulation of residual stressor impacts
generated upstream and augmented by dense development along
major river corridors. The Amazon shows the reverse, with impacts
from human-dominated source areas in Peru and Bolivia persisting
but progressively diluted downstream. Even sparsely settled basins
like the Lena in Siberia with generally low threat can show the impact
of development near the river mouth. The proliferation of densely
settled areas in the coastal zone including mega-cities means that its
many rivers show high threat over virtually their entire length (for
example, Paraı
´ba do Sul (Sa
˜o Paulo state), Pasig (Manila), Ogun
Our results agree with recent field surveys, underscoring the dire
state of river health. Recent sampling of rivers across the United States
showed impairment across 750,000 km (50%) of sampled river length
and demonstrated the coincidence of multiple stressors, with agricul-
tural factors predominant
. In China, 45% of major river reaches
surveyed in 2008 were moderately to badly polluted
. Reviews of
global pollution based on water monitoring
and modelling studies
have shown broadly similar patterns to our threat maps. Our results
are also congruent with previous threat assessments conducted at the
coarser catchment and ecoregional scales
Discussion), yet provide the much greater levels of spatial detail
needed for environmental planning and management.
Despite the variety of stressors that we considered, our study and all
previous assessments
of anthropogenic impacts are conservative
owing to insufficient information on pharmaceutical and other syn-
thetic compounds, mining, interbasin water transfers, and other com-
monplace stressors
. Our current inability to account for in-stream
transformations, stressor synergies
, concentrated impacts during
low flow periods, and threats to smaller streams (#Strahler order 5;
1:62,500 scale)
are additional limitations. Finally, uncertainties in
stressor data are inevitable, but our standardization procedures lim-
ited their influence on our results (Supplementary Information).
Chief determinants of global threat
Globally, the catchment disturbance, pollution, and water resource
development themes are spatially well correlated (r$0.75 for human
water security, P,0.001; r$0.62 for biodiversity, P,0.001;
n546,517 grid cells), reflecting congruent gradients of human activ-
ities and their impacts (Supplementary Table 3). Biotic factors are less
strongly correlated with other themes (r#0.37 for human water
security, P,0.001; r#0.44 for biodiversity, P,0.001), reflecting
the spatial decoupling of fish species introductions from human
population density (Supplementary Table 3) and the broad distri-
bution of inland fisheries. Incident threats to human water security
and biodiversity are themselves well correlated (Fig. 1), with the high-
est levels in heavily settled regions.
In areas of high incident threat (.0.75), water resource develop-
ment and pollution are dominant contributing themes for both
human water security and biodiversity (Fig. 3), and they typically
occur together. Their combined importance derives from the water-
borne nature of the stressors: water pollution distributed throughout
the world’s rivers is broadly coincident with the widespread presence
of engineering works that enable the overuse and mismanagement of
water in many locations. Catchment disturbance and biotic factors
have a secondary role in high incident threat areas as their stressors
often represent more localized effects.
High levels of incident human water security and biodiversity
threat emerge only from the spatial concordance of high scores for
many stressors (Fig. 3). Stressors within the catchment disturbance
and pollution themes generally act in unison across human water
security and biodiversity, highlighting shared sources of impact, with
cropland the predominant catchment stressor and nutrient, pesticide
and organic loads dominating pollution sources. For the remaining
themes, stressors act more independently, reflecting distinctions
between human water security and biodiversity perspectives.
Stressors associated with impoundments and flow depletion are the
clearest sources of biodiversity threat by directly degrading habitat,
while negligibly affecting human water security. These results high-
light the diverse and unique sets of stressor impacts confronting
rehabilitation efforts in high impact areas, and argue for replacing
current fragmentary approaches to management with integrative
strategies that deliberately alleviate multiple sources of threat
Reducing threats to human water security
Our incident threat maps do not reflect technological investments
that can improve human water security. To capture this effect, we
derived an ‘investment benefits factor’, depicting supply stabilization,
improved water services and access to waterways, then used it to
calculate an ‘adjusted human water security threat’. Comparison of
incident and adjusted human water security threats reveals that tech-
nological investments produce globally significant, positive impacts
on human water security and substantially reconfigure exposure to
threat (Fig. 4 and Supplementary Information). Highly developed
Distance to ocean (km)
Huang He
3,500 3,000 2,500 2,000 1,500 1,000 500 0
4,500 4,000 3,500 3,000 2,500 2,000 1,500 1,000
500 0
4,000 3,500 3,000 2,500 2,000 1,500 1,000 500 0
Mixture of
White + Blue
Nile waters
headwaters Settlements
on mainstem Aswan
High Dam
Atbara R.
4,000 3,000 2,000 1,000 05,000
Biodiversity threat index
Figure 2
Incident biodiversity threat transects from headwaters to ocean.
Distinctive patterns characterize each river system resulting from complex
spatial patterns of stressor loadings across the catchment plus mixing of higher
and lower concentration tributary waters through river networks. Transects
represent the collective impact of stressors operating within particular
development settings, and thus serve to diagnose the chief factorsgiving rise to
threat or to identify critical areas at risk, as shown for the Nile (Natl, National).
Threat indices depict conditions over the full basin at set distances from river
mouth, but can be reconfigured to track individual reaches or tributary sub-
30 SEPTEMBER 2010 | VOL 467 | NATURE | 557
Macmillan Publishers Limited. All rights reserved
regions with high incident threat (for example, United States, Western
Europe) often show much lower adjusted threat indices, gaining bene-
fit from massive investments in water infrastructure, the total value of
which is in the trillions of US dollars
. Investments by high-income
countries benefit 850 million people, lowering their exposure to high
incident threat by 95%, with corresponding values for upper middle-
income countries of 140 million and 23% (Table 1). Minimal invest-
ment in developing countries means that their vulnerability remains
high, with 3.4 billion people in these regions residing in areas showing
the highest adjusted threat category.
Our analysis is a spatial expression of the many water security
challenges facing the world’s poor, as identified in case studies, docu-
mentary evidence and global, although fragmentary, data
(Fig. 4).
Most of Africa, large areas in central Asia and countries including
China, India, Peru, or Bolivia struggle with establishing basic water
services like clean drinking water and sanitation
, and emerge here as
regions of greatest adjusted human water security threat. Lack of
water infrastructure yields direct economic impacts. Drought- and
famine-prone Ethiopia, for example, has 150 times less reservoir stor-
age per capita than North America
and its climate and hydrological
Pollution Watershed
Water resource
Human water security
1,000 2,000 3,000
Dam density
River fragmentation
Consumptive water loss
Human water stress
Agricultural water stress
Flow disruption
Soil salinization
Nitrogen loading
Phosphorus loading
Mercury deposition
Pesticide loading
Sediment loading
Organic loading
Potential acidication
Thermal alteration
Non-native shes (%)
Non-native shes (no.)
Fishing pressure
Aquaculture pressure
Livestock density
Impervious surfaces
Water resource developmentWatershed disturbance
Biotic factors
1,000 2,000 3,000
1,000 2,000 3,000
1,000 2,000 3,000
Aggregate score
ate score
Aggregate score
Aggregate score
ate score
Figure 3
Theme and driver contributions in areas where incident threat
exceeds the 75th percentile. High incident threat typically arises from the
spatial coincidenceof multiple themes and/or drivers of stress acting in concert.
Each aggregate score represents the number of grid cells exceeding the 75th
percentile for each individual theme or driver over the high incident threat
areas. Influence of each of the four themes (left)is relative to its contribution to
overall incident threat. For the individual drivers (right), scores are relative to
other drivers in the same theme. Bars summarize results over the entire
discharging landmass.
No appreciable ow
HWS threat
benets factor
HWS threat
HWS threat
Adjusted HWS threat
0.2 0.6
0.4 0.80
1 0.2 0.6
0.4 0.80
10.2 0.6
0.4 0.80
1 0.2 0.6
0.4 0.80
0.2 0.6
0.4 0.80
Figure 4
Shifts in spatial patterns of relative human water security threat
after accounting for water technology benefits. Inset maps illustrate the
analytical approach and net impact of investment over a north–south transect
(top). Incident human water security (HWS) threat is converted to reduced
threat (inset maps), which is then globally re-scaled into adjusted human water
security threat. The final map shows relative units: areas with substantial
technology investments have effectively limited exposure to threat whereas
regions with little or no investment become the most vulnerable in a global
context. Colour spectra depictthree measures of threat (increasing, blue to red)
and investment benefits (increasing, light to dark).
558 | NATURE | VOL 467 | 30 SEPTEMBER 2010
Macmillan Publishers Limited. All rights reserved
variability takes a 38% toll on gross domestic product (GDP)
. The
number of people under chronically high water scarcity, many of
whom are poor, is 1.7 billion or more globally
, with 1.0 billion
of these living in areas with high adjusted human water security threat
Contrasts between incident and adjusted human water security
threat are striking when considered relative to national wealth.
Incident human water security threat is a rising but saturating func-
tion of per capita GDP, whereas adjusted human water security threat
declines sharply in affluent countries in response to technological
investments (Fig. 5). The latter constitutes a unique expression of
the environmental Kuznets curve
, which describes rising ambient
stressor loads during early-to-middle stages of economic growth
followed by reduced loading through environmental controls insti-
tuted as development proceeds. The concept applies well to air pollu-
tants that directly expose humans to health risks, and which can be
regulated at their source
. The global investment strategy for human
water security shows a distinctly different pattern. Rich countries
tolerate relatively high levels of ambient stressors, then reduce their
negative impacts by treating symptoms instead of underlying causes
of incident threat.
The biodiversity dilemma
We find that 65% of global river discharge, and the aquatic habitat
supported by this water, is under moderate to high threat (.0.5). Yet,
we were unable to compute a globally meaningful estimate of adjusted
biodiversity threat due to the paucity of relevant data but also the
reality that much less comprehensive investment has been directed
to biodiversity conservation than to human water security
Limited global investment in environmental protection and rehab-
ilitation means that stresses on biodiversity for many locations go
unabated. In addition, the substantial reductions in incident human
water security threat through point-of-service strategies emphasizing
water supply stabilization and delivery incorporate some of the very
factors that negatively impact biodiversity through flow distortion
and habitat loss. This helps to explain why environmental Kuznets
curve benefits that typically rise with increasing levels of affluence do
not necessarily hold for fish biodiversity
or water quality
, and why
river restoration efforts often fail
. Indeed, Europe still suffers sig-
nificant biodiversity threat despite concerted, high-level efforts aimed
at achieving the contrary
The worldwide pattern of river threats documented here offers the
most comprehensive explanation so far of why freshwater biodiversity
is considered to be in a state of crisis
. Estimates suggest that at least
10,000–20,000 freshwater species are extinct or at risk
, with loss
rates rivalling those of previous transitions between geological epochs
like the Pleistocene-to-Holocene
. Although we have not established
causality, our results establish a precursor to future studies that could
link the role of stressors to biodiversity loss more directly.
Rising to a dual challenge
Given escalating trends in species extinction, human population, cli-
mate change, water use and development pressures
, freshwater sys-
tems will remain under threat well into the future. Without major
policy and financial commitments, stark contrasts in human water
security will continue to separate rich from poor. We remain off-pace
for meeting the Millennium Development Goals for basic sanitation
, a testament to the lack of societal resolve, when one con-
siders that a century of engineering know-how is available and returns
on investment in facilities are high
. For Organisation for Economic
Co-operation and Development (OECD) and BRIC (Brazil, Russia,
India and China) countries alone, 800 billion US dollars per year will
be required in 2015 to cover investments in water infrastructure, a
target likely to go unmet
. The situation is even more daunting for
biodiversity. International goals for its protection lag well behind
Table 1
Reconfiguring global exposure to incident human water security threat through technology investments
Income level*GDP (PPP){
US dollars per capita)
Global population
by income level{(%)
Fraction of population within each income level{where HWS threat .0.75
Incident HWS threat (%) Adjusted HWS threat (%)
Low ,1 7 43 96
Lower middle 1–5 61 85 88
Upper middle 5–10 14 79 61
High .10 18 90 5
Percentages were determined by summing populations within national-scale designations of income that were exposed initially to high levels of incident human water security (HWS) threat and then residual
adjusted human water security threat, after benefits were tabulated and results re-scaled globally. Differences in the last two columns indicate a major global-scale realignment of relative risk, with human water
security most assured for wealthy nations and least so for the world’s poor. Investments are represented by existing infrastructure comprising water supply, use and delivery services, plus access to waterways
(specific driver data sets and calculation procedures used are given in Supplementary Methods ‘Overview’).
*Approximated from World Bank categories
{Classifications are for 2008
{Computed over the discharging landmass.
GDP (PPP) 103 US dollars per capita
Incident threat
Reduced threat
Benecial effect
of investments
< 0.5
Relative threat to water security
0.0 <0.25 <0.5 <0.75 <1.0
Null expectation
Fraction of global population
Threat to human water security
Figure 5
Globally aggregatedhuman water security threat indices linked to
population and level of economic development. Investments in engineering
infrastructure and services improve water security, with their value expressed
here in reduced threat units. Net benefits accrue to only a fraction of global
population (top). Technology investments greatly benefit wealthy nations,
shifting them from most to least threatened (bottom). The fraction of global
population is over the discharging landmass. GDP (PPP) refers to annual gross
domestic product in 2008 at purchasing power parity exchange
, with
associated grid-cell means of incident human water security threat (red bars)
and reduced threat (yellow; see Fig. 4). Vertical lines represent ranges.
30 SEPTEMBER 2010 | VOL 467 | NATURE | 559
Macmillan Publishers Limited. All rights reserved
expectation and global investments are poorly enumerated but likely
to be orders of magnitude lower than those for human water secur-
, leaving at risk animal and plant populations, critical habitat
and ecosystem services that directly underpin the livelihoods of many
of the world’s poor
. Left unaddressed, these linked human water
security–biodiversity water challenges are forecast to generate social
instability of growing concern to civil and military planners
Our threat maps enable spatial planning to enhance water security
for humans and nature
. Although our intent is not to develop formal
priorities to mitigate risk, we present a final analysis that is instructive
in considering options. Comparing adjusted human water security to
incident biodiversity threats highlights regions where either human
water security or biodiversity challenges, or their conjunction, pre-
dominate (Fig. 6). Such patterns are important to identify because the
main stressors determining human water security and biodiversity
threat are sometimes distinct, thus requiring different and potentially
conflicting management solutions (Fig. 3).
In remote areas with low indices of both human water security and
biodiversity threat, preserving critical habitat and ecosystem pro-
cesses may be the single best strategy to contain future risk, yet the
issue of who will pay for such protection is unresolved
. Solutions
for densely settled regions will be more elusive. Although there may be
easy consensus on controlling factors that lead to both human water
security and biodiversity threat (for example, pollution), the decision
to construct large-scale dams is a prime example of how development
pressure is often at odds with biodiversity conservation and thus more
. In populated regions of the developed world, existing
human water security infrastructure will require re-engineering to
protect biodiversity while retaining human water services. Across
the developing world, establishing human water security for the first
time while preserving biodiversity constitutes a dual challenge, best
met through integrated water resource management
that expressly
balances the needs of humans and nature. Although our results offer
prima facie evidence that society has failed to institute this principle
broadly, there are promising, cost-effective approaches to preserve
and rehabilitate ecosystems
. Engineers, for instance, can re-work
dam operating rules to maintain economic benefits while simulta-
neously conveying adaptive environmental flows for biodiversity
Protecting catchments reduces costs for drinking water treatment,
whereas preserving river floodplains sustains valuable flood protec-
tion and rural livelihoods
. Such options offer developing nations the
opportunity to avoid the high environmental, economic and social
costs that heavily engineered water development systems have pro-
duced elsewhere
The need to mobilize financial resources to support integrated
approaches remains urgent, lest further deterioration of fresh water
becomes the accepted norm
. Habitat monitoring
and spatially
explicit species inventories
are essential in evaluating the success of
and detecting the emergence of new challenges. Trade-
offs and difficult choices involving competing stakeholders are already
and resolving these dilemmas more effectively
requires high-resolution spatial approaches that engage policymakers
and water managers at scales relevant to their decisions, including sub-
national administrative units, river basins and individual stream
reaches. Uniting our current approach with ocean-based assess-
will identify areas where improved freshwater and land
management would benefit the world’s impaired coastal zones. If cli-
mate mitigation is any guide, a generational timeframe may be neces-
sary to stimulate sufficient political willpower to address the global
river health challenge. In the meantime, a substantial fraction of the
world’s populationand countless freshwater species remainimperilled.
Maps of incident threat to river systems were based on spatially explicit data
depicting 23 stressors (drivers), grouped into four major themes representing
environmental impact. We chose drivers based on their documented role in
degrading river systems and the availability of global-scale information with
sufficient fidelity and spatial resolution. Conceptual and computational details
are given in Supplementary Methods. Briefly, impacts of individual drivers ori-
ginated from the spatial distribution of loadings onto 309(latitude 3longitude)
grid cells covering the actively discharging portion of global landmass bearing
local runoff or major river corridor flow (46,517 cells representing 99.2 million
). Driver loadings were routed down digital river networks
, accounting for
new stressor inputs, and dilution or concentration from tributary mixing, based
on spatial changes in river discharge determined from net precipitation and
abstraction, where appropriate. Global, high-resolution maps of each driver were
then standardized using a cumulative density function that ranked all grid cells,
yielding final driver scores between 0 and 1 that reflect the relative stressor level
on each cell across the globe. The re-scaled driver scores were combined into
overall incident threat indices using a two-tiered relative weight matrix derived
from expert opinion (first among drivers within each theme, then among
themes). We used separate weights to capture differences between human water
security and biodiversity perspectives on each driver and theme (Supplementary
Table 1). Separately, we applied the same procedure to an additional set of five
drivers to derive an index of the beneficial effects of water-related capital and
engineering investments
in alleviating threats to human water security. By
applying this investment benefits factor to the incident human water security
threat index and re-scaling the global results, we produced the map of relative
adjusted human water security threat (Fig. 4). There is insufficient information to
map corresponding adjustments to incident biodiversity threat.
Biodiversity threat
Low High
Human water
security threat
High Low
Figure 6
Prevailing patterns of threat to human water security and
biodiversity. Adjusted human water security threat is contrasted against
incident biodiversitythreat. Much of the developed world faces the challenge of
reducing biodiversity threat and protecting biodiversity, while maintaining
established water services. The developing world shows tandem threats to
human water security and biodiversity, posing an arguably more significant
challenge. Large, contiguous areas of low threat to biodiversity and human
water security remain where dense population and agriculture are absent.
These contrasts help to identify target regions and investment strategies to
enhance water stewardship and biodiversity protection
. In this Figure, a
breakpoint of 0.5 delineates low from high threat.
560 | NATURE | VOL 467 | 30 SEPTEMBER 2010
Macmillan Publishers Limited. All rights reserved
Received 21 January; accepted 19 August 2010.
1. Meybeck, M. Global analysis of river systems: from Earthsystem controls to
Anthropocene syndromes. Phil. Trans. R. Soc. Lond. B, (2003).
2. World Water Assessment Programme. Water in a Changing World. The United
Nations World Water Development Report 3 (UNESCO, 2009).
3. Vo
¨smarty, C. J. et al. in Millennium Ecosystem Assessment Vol. 1, Ch. 7, 165–207
(Island Press, 2005).
4. Karl, T. R., Melillo, J. M. & Peterson, T.C. (eds) Global Climate Change Impacts in the
United States (Cambridge Univ. Press, 2009).
5. Framing Committee of the Global Water System Project. Humans transforming
the global water system. Eos AGU Trans. 85, 513–514 (2004).
6. United Nations Development Programme. HDR 2006—Beyond Scarcity: Power,
Poverty and the Global Water Crisis (UNDP, 2006).
7. Abell, R. et al. Freshwater ecoregions of the world: a new map of biogeographic
units for freshwater biodiversity conservation. Bioscience 58, 403–414 (2008).
8. International Union for Conservation of Nature and Natural Resources. The IUCN
Red List of Threatened Species 2009. 1 Æhttp://www.iucnredlist.orgæ(2009).
9. Convention on Biological Diversity. Text of the Convention on Biological Diversity
10. United Nations Environment Programme. Report of the third ad hoc
intergovernmental and multi-stakeholder meeting on an intergovernmental
science-policy platform on biodiversity and ecosystemservices. UNEP/IPBES/3/3
11. Gleick, P. H. Global freshwater resources: soft-path solutions for the 21st century.
Science 302, 1524–1528 (2003).
12. Sullivan, C. & Meigh, J. Targeting attention on local vulnerabilities using an
integrated index approach: the example ofthe Climate Vulnerability Index. Water
Sci. Technol. 51, 69–78 (2005).
13. Esty, D. et al. The 2005 Environmental Sustainability Index: Benchmarking National
Environmental Stewardship (Yale Center for Environmental Law and Policy, 2005).
14. Esty, D. et al. The Pilot 2006 Environmental Performance Index Report (Yale Center
for Environmental Law & Policy and CIESIN, 2006).
15. Vo
¨smarty, C. J., Green, P., Salisbury, J. & Lammers, R. Global water resources:
vulnerability from climate change and population growth. Science 289, 284–288
16. Halpern, B. S. et al. A global map of humanimpact on marine ecosystems.Science
319, 948–952 (2008).
17. Halpern, B. S. et al. Global priority areas for incorporating land–sea connections in
marine conservation. Conser. Lett. 2, 189–196 (2009).
18. Sanderson, E. W. et al. The human footprintand the last of the wild. Bioscience 52,
891–904 (2002).
19. Food and Agriculture Organization. Water Monitoring: Mapping Existing Global
Systems & Initiatives (FAO, 2006).
20. Vo
¨smarty, C. J. Global water assessment and potential contributions from earth
systems science. Aquat. Sci. 64, 328–351 (2002).
21. Dudgeon, D. et al. Freshwater biodiversity: importance, threats, status and
conservation challenges. Biol. Rev. Camb. Philos. Soc. 81, 163–182 (2006).
22. Vo
¨smarty, C. J., Douglas, E. M., Green, P. A. & Revenga, C. Geospatial indicators of
emerging water stress: an application to Africa. Ambio 34, 230–236 (2005).
23. Fekete, B. M., Vo
¨smarty, C. J. & Lammers,R. B. Scaling gridded river networks for
macroscale hydrology: development, analysis, and control of error. Wat. Resour.
Res. 37, 1955–1967 (2001).
24. US-EnvironmentalProtection Agency.The Quality of Our Nation’s Waters. EPA-841-
R-02–001 (US EPA, 2000).
25. Ministry of Environmental Protection.The State of the Environmentof China in 2008
t20090618_152932.htmæ(Ministry of Environmental Protection, The People’s
Republic of China, 2009).
26. UNEP GEMS/Water Programme. Water Quality for Ecosystem and Human Health
2nd edn (UNEP GEMS/Water Programme, 2008).
27. Seitzinger, S. P., Harrison, J. A., Dumont, E., Beusen, A. H. W. & Bouwman, A. F.
Sources and deliveryof carbon, nitrogen, and phosphorus to the coastal zone: an
overview of Global Nutrient Export from Watersheds (NEWS) models and their
application. Glob. Biogeochem. Cycles 19, GB4S01 (2005).
28. World ConservationMonitoring Centre.Freshwater Biodiversity: a Preliminary Global
Assessment. WCMC Biodiversity Series No. 8 (World Conservation Press, 1998).
29. Palmer, M. A. & Filoso, S. Restoration of ecosystem services for environmental
markets. Science 325, 575–576 (2009).
30. Ashley, R. & Cashman, A. The impacts of change onthe long-term future demand
for water sector infrastructure. In: Infrastructure to 2030: Telecom, Land Transport,
Water and Electricity Ch. 5 (Organization for Economic Co-operation and
Development, 2006).
31. WHO/UNICEF. Progress on Sanitation and Drinking-Water: 2010 Update. Joint
Monitoring Programme for Water Supply and Sanitation (World Health
Organisation/UNICEF, 2010).
32. Grey, D. & Sadoff, C. W. Water for Growthand Development. ThematicDocuments of
the IV World Water Forum (Comisio
´n Nacional del Agua: Me
´xico, 2006).
33. Dinda, S. Environmental Kuznets curve hypothesis: a survey. Ecol. Econ. 49,
431–455 (2004).
34. The Global Environmental Facility. Financing the Stewardship of Global Biodiversity
(GEF, 2008).
35. Butchart, S. H. M. et al. Global biodiversity: indicators of recent declines. Science
328, 1164–1168 (2010).
36. Clausen, R. & York, R. Global biodiversity decline of marine and freshwater fish: a
cross-national analysis of economic,demographic, and ecological influences. Soc.
Sci. Res. 37, 1310–1320 (2008).
37. Tockner, K., Uehlinger, U. & Robinson,C. T. (eds) Rivers of Europe (Academic,2009).
38. Balian, E. V., Le
ˆque, C., Segers, H. & Martens, K. The freshwater animal diversity
assessment: an overview of the results. Hydrobiologia 595, 627–637 (2008).
39. Ricciardi, A. & Rasmussen, J. B. Extinction rates of North American freshwater
fauna. Conserv. Biol. 13, 1220–1222 (1999).
40. Kottelat, M. & Freyhof, J. Handbook of European Freshwater Fishes (Kottelat and
Freyhof, 2007).
41. Jelks, H. L. et al. Conservation status of imperiled North American freshwater and
diadromous fishes. Fisheries 33, 372–407 (2008).
42. Strayer, D. L. & Dudgeon, D. Freshwater biodiversity conservation: recent progress
and future challenges. J. N. Am. Benthol. Soc. 29, 344–358 (2010).
43. Zalasiewicz, J. et al. Are we now living in the Anthropocene? GSA Today 18, 4–8
44. Steffen, W., Crutzen, P. J. & McNeill, J. R. The Anthropocene: are humans now
overwhelming the great forces of nature? AMBIO 36, 614–621 (2007).
45. Brooks, T. M. et al. Global biodiversity conservation priorities. Science 313, 58–61
46. Reid, W. V. et al. Millennium Ecosystem Assessment: Ecosystems and Human Well-
Being—Synthesis Report (World Resources Institute, 2005).
47. Brown, O. & Crawford,A. Rising Temperatures, Rising Tensions: Climate Change and
the Risk of Violent Conflict in the Middle East (International Institute for Sustainable
Development, 2009).
48. World Commission on Dams. Dams and Development: A New Framework for
Decision-Making (Earthscan, 2000).
49. Arthington, A. H., Bunn, S. E., Poff, N. L. & Naiman, R. J. The challenge of providing
environmental flow rules to sustain river ecosystems. Ecol. Appl. 16, 1311–1318
50. The World Bank.. Country Classifications Æ
country-classificationsæ(17 May 2010).
Supplementary Information is linked to the online version of the paper at
Acknowledgements We thank A. DeSherbinin, L. Poff, C. Revenga, J. Melillo and O.
Young for comments on the manuscript; D. Allan, R. Abell, J. Bogardi, M. Meybeck, W.
Wollheim, R. F. Wright, D. Boswell, R. Lacey, N. Schneider and D. Vo
¨smarty for advice;
and D. Dube and B. Fekete for technical support. Grant support for database and tool
developmentwas from NASA Inter-Disciplinary ScienceProgram Grant NNX07AF28G,
with additional support from the NSF Division of EarthSciences (Hydrologic Sciences
Program Award #0854957) and Global Environment Facility (UPI 00345306). P.B.M.
was supported by a D.H. Smith Fellowship. Financial and logistical support for expert
group meetings and communications was from the Global Water System Project
(Bonn), DIVERSITAS-freshwaterBIODIVERSITY (Paris), NSF BestNet, and Australian
Agency forInternational Development (AusAID) throughthe Australian Water Research
Facility. Conference facilities were provided by the Swiss Federal Institute of Science &
Technology (Eawag) and The City College of New York/CUNY.
Author Contributions All authors contributed to project conceptualization during
workshops led by C.J.V. C.J.V. designed the global analysis, and P.B.M., A.P., P.G. and
M.O.G. designed and implemented the analytical approach with essential input from
S.E.B., D.D., C.A.S., P.M.D. and C.R.L. A.P., P.G. and S.G. developed the database and
mapping tools.Several authors led a separatecomponent of data set developmentand
all providedquality assurance.C.J.V., P.B.M. andM.O.G. wrote the manuscriptwith input
from all authors.
Author Information Reprints and permissions information is available at The authors declare no competing financial interests.
Readers are welcome to comment on the online version of this article at Correspondence and requests for materials should be
addressed to C.J.V. (
30 SEPTEMBER 2010 | VOL 467 | NATURE | 561
Macmillan Publishers Limited. All rights reserved
Global threats to human water
security and river biodiversity
C. J. Vo
¨smarty, P. B. McIntyre, M. O. Gessner, D. Dudgeon,
A. Prusevich, P. Green, S. Glidden, S. E. Bunn, C. A. Sullivan,
C. Reidy Liermann & P. M. Davies
Nature 467, 555–561 (2010)
In this Article, the full present address for author P. B. McIntyre was
inadvertently missing from the bottom of the page. The correct pre-
sent address is: Center for Limnology, University of Wisconsin,
Madison, Wisconsin 53706, USA. This has been corrected in the
online PDF.
Macmillan Publishers Limited. All rights reserved

Supplementary resource (1)

... 3. According to recent studies, approximately 80% of the world's population is currently facing severe threats to water security and the destruction of river habitats (Vörösmarty et al., 2010). The World Water Council estimates that more than half of the world's rivers are polluted or at risk of drying up. ...
... As one of the fundamental components of the Earth's natural ecosystem, surface water plays a critical role in maintaining biodiversity, ecological balance, and the development of human societies [47]. Due to its wide spatial and temporal distribution, using satellite imagery to detect and map the global surface water is a feasible and conve-* corresponding author. ...
Full-text available
Global surface water detection in very-high-resolution (VHR) satellite imagery can directly serve major applications such as refined flood mapping and water resource assessment. Although achievements have been made in detecting surface water in small-size satellite images corresponding to local geographic scales, datasets and methods suitable for mapping and analyzing global surface water have yet to be explored. To encourage the development of this task and facilitate the implementation of relevant applications, we propose the GLH-water dataset that consists of 250 satellite images and manually labeled surface water annotations that are distributed globally and contain water bodies exhibiting a wide variety of types (e.g., rivers, lakes, and ponds in forests, irrigated fields, bare areas, and urban areas). Each image is of the size 12,800 $\times$ 12,800 pixels at 0.3 meter spatial resolution. To build a benchmark for GLH-water, we perform extensive experiments employing representative surface water detection models, popular semantic segmentation models, and ultra-high resolution segmentation models. Furthermore, we also design a strong baseline with the novel pyramid consistency loss (PCL) to initially explore this challenge. Finally, we implement the cross-dataset and pilot area generalization experiments, and the superior performance illustrates the strong generalization and practical application of GLH-water. The dataset is available at
... Freshwater ecosystems appear more vulnerable to biodiversity loss due to many and heterogeneous pressures such as overexploitation, water pollution, habitat degradation, flow modification and exotic species introductions (Vörösmarty et al., 2010;Carpenter et al., 2011;Dudgeon, 2019), and due to the high number of endemic and rare species in a limited spatial extension (Gleick, 1998;Balian et al., 2008;Collen et al., 2014). Indeed, reserve networks were not primarily designed to protect freshwaters, and therefore may not adequately address its biodiversity and related threats, such as, non-native species impacts, water flow changes, habitat alterations, contaminants from upstream stream stretches, among others (Chessman, 2013;Hermoso et al., 2015). ...
Full-text available
Protected areas (PAs) are the cornerstones of global biodiversity conservation efforts, but to fulfil this role they must be effective at conserving both habitat and species. Among protected taxa, freshwater fish are exposed to multiple disturbances and are considered one of the most endangered. The Natura 2000 reserves network was established with the aim of preserving biodiversity across Europe, but few assessments have been made on its effectiveness on the conservation of freshwater fish species. We tested the hypothesis that fish community is exposed to less anthropogenic pressures within the Natura 2000 sites than outside, hosting a higher number of native species and maintain lower number of non-native species. We tested these hypotheses considering 3,777 sampling sites, found across the entire Italian territory. Results showed that PAs did not guarantee less anthropogenic impacts and higher fish species richness than outside PAs, suggesting that PAs are not a panacea for anthropogenic pressures and safeguarding fish diversity. Nevertheless, more caution should be applied to the management measures and the design of new PAs due to the limitations of the protection of a single stretch within a whole river ecosystem. Moreover, the impossibility to operate any management of invasive fish species on the broad scale of a whole river basin is likely the most limiting factor to fish biodiversity conservation in Italy. Finally, it is also necessary to extend the analysis to other basins and Natura 2000 sites in Europe.
... Because of overpopulation and associated human induced growth, inland wetlands in aquatic habitats have been easily destroyed, and interconnection among wetland habitats has decreased (Davidson 2014;Gibbs 2000;Mori et al 2018a, b). Understanding and mapping wetland distribution for broadscale valuations is hence a key initial stage concerning crucial and ranking exact conservation requests (Nel et al. 2007;Vörösmarty et al. 2010). In the last few decades, land use land cover changes caused by humans assumed responsibility for wetland deterioration. ...
Full-text available
The wetland stagnation is the premise of the wetland depth (WD) but is lacking in detail. The research looks into the correlation of stagnant wetland’s depth and their ecological status in the Central Tamil Nadu District (CTND) because of few studies. Seventy-five chosen stagnant wetlands are hydrologically isolated; depths were categorized into less than 5 ft., 6 to 10 and above 10 ft., surveyed by the range of methods from districts such as Karur (KD), Namakkal (ND) and Tiruchirappalli (TD). The human disturbance score (HDS) is categorized as least impacted (0–33), moderately impacted (33–67) and highly impacted (67–100). The impacts of land use and land cover (LULC) changes over 9 years (2010–2019) through the maximum likelihood method. Overall, 54% of wetland depths (WD) were less than 5 ft.; 25.6% were 6–10 ft. and 20.2% were 100 ft. District-wise, wetland degradation was the utmost in the TD, followed by ND and KD. Except in KD, the remaining district wetlands were of MI category with diverse HDS. The correlation test revealed a positive relationship between WD against the alteration of the buffer zone, habitat, hydrology and HDS. However, it is a negative relationship between landscape alteration and wetland pollution. The impacts of land use and land cover (LULC) changes confirm that severe decline in wetlands habitat and water bodies’ area is due to built-up area, cultivated land expansion and increasing population. Our study provided evidence that the WD is connected to wetland conditions that have a quantitative influence, and the ramifications of the findings were examined in the context of local development planning. Additional research will be needed due to limited surveyed wetlands with similar geographical locations.
Full-text available
درجهان معاصر با توسعۀ شهریِ بی‌وقفه‌ای مواجه هستیم که با آسیب به اکوسیستم‌های طبیعی درون‌شهری، شرایط اکولوژیکی شهرها را دچار اختلال کرده است. رودخانه‎های درون‌شهری اکوسیستم‌های طبیعی هستند که ماهیت اکولوژیکی دارند و بر بهبود شرایط اکولوژیکی شهرها اثر می‌گذارند. چارچوب شهرسازی اکولوژیک بر تداوم ساختارهای اکولوژیکی اکوسیستم‌های طبیعی در شهرها تأکید می‌کند و در جهت بهسازی آنها برنامه‌ریزی کرده و راهبردهایی تدوین می‌نماید. این پژوهش در چارچوب شهرسازی اکولوژیک بر بهسازی اکوسیستم رودخانه‎های شهری متمرکز شده، با مرور ادبیات تحقیق به بررسی مبانی نظری شهرسازی اکولوژیک، ماهیت اکولوژیکی رودخانه‎ها، آسیب‌های اکولوژیکی ناشی از توسعه‌های شهری و بهسازی رودخانه‎های شهری پرداخته می‌شود. سپس با روش قیاسی-استنتاجی، براساس منابع معتبر علمی، مبتنی‌بر نظر پژوهشگران، مؤلفه‌ها در جهت بهسازی اکولوژیک رودخانه‎های شهری مبتنی‌بر فرایند استخراج می‌شود. در نهایت به روش استنتاجی، براساس مؤلفه‌های اکولوژیک، راهبردهایی در مقیاس کلان و خُردِ برنامه‌ریزی به منظور بهسازی مجدد و حفاظت از اکوسیستم رودخانه‎ها و کرانه‌ها و اراضی مجاور، افزایش انعطاف‌پذیری اکوسیستم رودخانه در مواجهه با اغتشاشات اقلیمی آینده و جلوگیری از تداخل انسانی در فرایندهای طبیعی تدوین می‌شود. شناخت دلایل اصلی تخریب اکوسیستم، حفاظت از سلامت رودخانه، بازیابی مجدد ژئومورفولوژی رودخانه در شهر، ایجاد واتصال شبکه‌های اکولوژیکی زیستی، ممانعت از ورود فاضلاب و روان‎آب آلودۀ شهری، کنترل سیلاب با حفظ شرایط اکوسیستم رودخانه، برنامه‌ها و اقدامات بهسازی متناسب با توسعۀ شهری، تغییر نگرش مردم در حفاظت رودخانه و محدودیت حضور شهروندان در حریم آن، راهبردهایی در مقیاس کلان برنامه‌ریزی و اجرایی هستند که به‌واسطۀ راهبردهایی در مقیاس خُرد میسر می‌شوند تا در برنامه‌ریزی‌های توسعۀ شهری، با شرایط مشابه، مورد استفاده قرار گیرند و شهرسازی اکولوژیکْ آیندۀ شهرهای معاصر شود.
This paper documents an externality from the agricultural use of the most widely applied herbicide in the world—glyphosate—on birth outcomes of surrounding populations. We focus on the subclinical effects of water contamination in areas distant from the original locations of application. Our identification relies on: (i) the regulation allowing the introduction of genetically modified seeds in Brazil; (ii) the potential gain in municipality-level productivity from adoption of genetically modified soybean seeds and the strong complementary between these seeds and glyphosate; and (iii) the direction of water flow within water basins. We document a significant deterioration in birth outcomes for populations downstream from locations that are likely to have increased relatively more the use of glyphosate. According to our preferred specification, the average increase in glyphosate use in the sample during 2000–10 period led to an increase of 5% of the average in infant mortality rate.
Full-text available
Accounting for natural differences in flow variability among rivers, and understanding the importance of this for the protection of freshwater biodiversity and maintenance of goods and services that rivers provide, is a great challenge for water managers and scientists. Nevertheless, despite considerable progress in understanding how flow variability sustains river ecosystems, there is a growing temptation to ignore natural system complexity in favor of simplistic, static, environmental flow ''rules'' to resolve pressing river management issues. We argue that such approaches are misguided and will ultimately contribute to further degradation of river ecosystems. In the absence of detailed empirical information of environmental flow requirements for rivers, we propose a generic approach that incorporates essential aspects of natural flow variability shared across particular classes of rivers that can be validated with empirical biological data and other information in a calibration process. We argue that this approach can bridge the gap between simple hydrological ''rules of thumb'' and more comprehensive environmental flow assessments and experimental flow restoration projects.
Full-text available
Freshwater habitats occupy ,1% of the Earth's surface, yet are hotspots that support ,10% of all known species, and ,M of vertebrate species. Fresh waters also are hotspots for human activities that have led to widespread habitat degradation, pollution, flow regulation and water extraction, fisheries overexploitation, and alien species introductions. These impacts have caused severe declines in the range and abundance of many freshwater species, so that they are now far more imperiled than their marine or terrestrial counterparts. Here, we review progress in conservation of freshwater biodiversity, with a focus on the period since 1986, and outline key challenges for the future. Driven by rising conservation concerns, freshwater ecologists have conducted a great deal of research over the past 25 y on the status, trends, autecology, and propagation of imperiled species, threats to these species, the consequences of biodiversity loss for ecosystem functioning, metapopulation dynamics, biodiversity hotspots, reserve design, habitat restoration, communication with stakeholders, and weaknesses of protective legislation. Nevertheless, existing efforts might be insufficient to stem the ongoing and coming multitude of freshwater extinctions. We briefly discuss 4 important challenges for freshwater conservation. First, climate change will imperil both freshwater species and human uses of fresh water, driving engineering responses that will further threaten the freshwater biota. We need to anticipate both ecological and human responses to climate change, and to encourage rational and deliberate planning of engineering responses to climate change before disasters strike. Second, because freshwater extinctions are already well underway, freshwater conservationists must be prepared to act now to prevent further losses, even if our knowledge is incomplete, and engage more effectively with other stakeholders. Third, we need to bridge the gap between freshwater ecology and conservation biology. Fourth, we suggest that scientific societies and scholarly journals concerned with limnology or freshwater sciences need to improve their historically poor record in publishing important papers and influencing practice in conservation ecology. Failure to meet these challenges will lead to the extinction or impoverishment of the very subjects of our research.
Protecting the worlds freshwater resources requires diagnosing threats over a broad range of scales, from global to local. Here we present the first worldwide synthesis to jointly consider human and biodiversity perspectives on water security using a spatial framework that quantifies multiple stressors and accounts for downstream impacts. We find that nearly 80% of the worlds population is exposed to high levels of threat to water security. Massive investment in water technology enables rich nations to offset high stressor levels without remedying their underlying causes, whereas less wealthy nations remain vulnerable. A similar lack of precautionary investment jeopardizes biodiversity, with habitats associated with 65% of continental discharge classified as moderately to highly threatened. The cumulative threat framework offers a tool for prioritizing policy and management responses to this crisis, and underscores the necessity of limiting threats at their source instead of through costly remediation of symptoms in order to assure global water security for both humans and freshwater biodiversity.
Water is like no other commodity, excepting food, in that it is essential to human life. The greatest challenges facing us relate to the conditions in which we live, how we are nourished and sheltered. Water is a central issue in a world that is increasingly urbanised and has a rising population to feed and seemingly ever increasing risks. The 20th century saw global population triple and the development of megacities. Water consumption rose, both in total amount needed and in per capita demand. Increasing pollution loads and abstractions have outstripped the assimilative capacity of ecosystems. Across the world, urbanisation has progressed through stages of ever denser habitation. Water service and infrastructure are meant to keep pace with these changes in developed countries: Typically, there is an assumption that the services will follow the newest needs in terms of how people work and live. (For a fuller discussion see Juuti and Katko, 2005.) Ironically, in many of the countries, water is undervalued by the citizens who live in towns and cities because it is readily available from the tap. Once used, it is then flushed away down the toilet or the sink and is never seen or thought of again. Up to one-third of the water supplied to domestic properties is used for toilet flushing and a further significant proportion is used for purposes other than drinking; in some countries, including Australia, water used for domestic gardening can constitute more than 50% of domestic use. Worldwide, the demand for water for irrigation is now consuming some 75% of the total abstracted. In anticipation of this explosion in water use there was significant investment in the past in the provision and operation of water infrastructure, much of it in informal and low-technology groundwater pumping, some of which helps grow cheap crops exported from the developing countries to the developed world. Worryingly, much of this water use is unsustainable (New Scientist, 2006).