advancing the conservation of freshwater biodiversity through...

Advancing The ConservationOf Freshwater Biodiversity

Through Ecoregion Planning

An information paper summarizing WWF’sSourcebook for Conducting Biological Assessments and Developing Biodiversity Visions for Ecoregion

Conservation – Volume II: Freshwater EcoregionsJune 2002

2 Advancing The Conservation Of Freshwater Biodiversity Through Ecoregion Planning

What does the Sourcebook contain?

The WWF Sourcebook for Freshwater Ecoregions is acompanion volume to the Workbook for TerrestrialEcoregions published by WWF in 2000. While theoverall process of ecoregion conservation is broadlysimilar for terrestrial, freshwater, and marine ecosys-tems, there are some crucial differences. This secondvolume is essentially a technical manual that guidesusers through the theory and practice of ecoregionconservation for freshwater ecosystems worldwide.Its 201 pages include:

� An introduction to ecoregion conservation and thespecial requirements of ecoregion conservation forfreshwater ecosystems;

� Guidance on integrating freshwater and terrestrialecoregion conservation and discussion of the rela-tionship between ecoregion conservation and inte-grated river basin management;

� Guidance on how to conduct a freshwater biologi-cal assessment and develop a ‘vision’ at the ecore-gional scale;

� Illustrated examples of freshwater biologicalassessments as part of ecoregion conservation;

� Extensive references and internet links.

Who is it aimed at?

The Sourcebook for Freshwater Ecoregions is relevantto anyone engaged in conservation planning for fresh-water ecosystems, including local, regional andnational authorities, the water industry, and non-gov-ernmental organizations. It is recommended readingfor those conducting biological assessments or devel-oping biodiversity visions in any ecoregion, regardlessof whether the ecoregion is formally designated asbeing freshwater, terrestrial, or coastal/marine. TheSourcebook will help those engaged in planning forterrestrial ecoregions to incorporate conservation offreshwater biodiversity, while practitioners working oncoastal/marine ecoregions will find important infor-mation on coastal river basins.

Where is it available?

The Sourcebook can be obtained as a pdf file onCD–ROM from WWF-US ([email protected]), or as adownloadable pdf file via the WWF internet athttp://www.panda.org/livingwaters/pubs.html.

Summary of key issues

1. Defining ‘freshwater’ ecosystems

For the purposes of the Sourcebook, freshwaterecosystems include all inland bodies of water,whether fresh or saline, including – among others –lakes, rivers, and associated wetlands. The Sourcebookalso defines wetlands as “those transitional landsbetween terrestrial and aquatic systems where thewater table is usually at or near the surface, or theland is covered by shallow water”. It is acknowledgedthat the wide range of definitions for the terms fresh-water and wetlands may generate some confusion.Thus, commonly agreed and understood definitionsare important for everyone involved in a given ecore-gion conservation project.

2. Why a focus on freshwater ecoregions?

While rivers, lakes, and wetlands contain a mere 0.01%of the Earth’s water, these ecosystems support a dis-proportionately large part of global biodiversity.Freshwater fishes alone account for approximatelyone quarter of all living vertebrate species. It is esti-mated that there are 44,000 scientifically namedspecies of freshwater biota.

Tallies of endangered species indicate that freshwaterbiodiversity is generally more threatened than terres-trial biodiversity. For example, of those species consid-ered in The World Conservation Union’s (IUCN) RedList for 2000, 20% of amphibians and 30% of fishes(mostly freshwater) were considered threatened. At aregional scale, the projected future extinction rate forNorth American freshwater fauna is about five times

3An information paper

greater on average than that for terrestrial fauna, andthree times higher than for coastal/marine mammals.

Freshwater biodiversity faces a broad range of threats.These include the direct impacts of dams, exotic species,overfishing, pollution, stream channelization, waterwithdrawals and diversions, as well as the indirect con-sequences of terrestrial activities such as logging, agri-culture, industry, housing development, and mining.Action is needed urgently; yet, until recently, conserva-tion planning to protect freshwater biodiversity hasbeen more of an afterthought than a prime considera-tion. WWF and its partners are seeking to reverse thistrend by focusing on freshwater habitats and specieswithin the framework of ecoregion conservation.

Ecoregions designated as terrestrial or coastal/marineare likely to include a freshwater component. Becauseof the real differences that exist between freshwaterecoregion planning and the terrestrial ecoregions withwhich practitioners are most familiar, freshwaterspecies and habitats within such ecoregions should beconsidered from the start. Failure to do so will presentdifficulties later on.

3. The concept of ecoregion conservation

An ecoregion is a relatively large unit of predomi-nantly land or water that contains a distinct assem-blage of natural communities sharing many speciesand environmental conditions.

Ecoregions are suitable units for biodiversity conserva-tion planning because they:

� enable the ecological driving forces of biodiversityto be analysed and addressed;

� enable the conservation needs of wide rangingspecies, or species that require particularly largeareas of habitat, to be addressed effectively;

� enable the biological communities representativeof an entire region to be identified;

� enable threats to biodiversity that operate acrossan entire ecoregion to be addressed coherently,rather than on an ad hoc site-by-site basis;

� enable identification of key sites and issues for invest-ment of conservation efforts, and a better under-standing of the role that specific projects can andshould play in long-term biodiversity conservation.

The cornerstone of ecoregion conservation is a biodi-versity vision that goes far beyond the current para-digm of protected sites and management practices.Thus, in every ecoregion, it is important to ask, from aconservation perspective, What should the ecoregionlook like 10, 20, and 50 years from now?

To define a vision, conservation managers or practi-tioners are challenged to characterize ‘success’ interms of achieving effective conservation of an ecore-gion’s biodiversity within a given timeframe. This, inturn, will depend greatly on the findings of a biologi-cal assessment – a record of the distribution ofspecies, communities, and habitats in the ecoregion,of ecological processes sustaining that biodiversity,and of current and future threats to its maintenance.

Ecoregion conservation focuses on the maintenance ofecological processes, important evolutionary phenom-ena, higher-order diversity (i.e. at the genus and familylevels), and rare habitat types, in addition to more tradi-tional indicators such as species richness and endemism.Intact or near-intact species assemblages are given par-ticular prominence because of their increasing rarityworldwide. There is also an emphasis on ‘keystone’species and habitats, the loss or degradation of whichwould have a disproportionately large negative effect onthe ecoregion as a whole, through consequent impactson other species, habitats, or ecological processes.

Throughout the Sourcebook, representation – captur-ing the full range of biodiversity of a given biogeo-graphic unit within a system of protected areas – isemphasized, as is the importance of conservation tar-gets. With the intention of focusing activities as far aspossible, the following biodiversity-driven headingsare recommended for the establishment and group-ing of specific targets:

� Distinct communities,habitats,and species assemblages;� Large expanses of intact habitats, and intact

native biotas;� Keystone habitats,species,and processes;� Other species of special concern;� Large-scale ecological phenomena.

4. The extent of freshwater ecoregions

Satellite imagery permits coarse representation of themajor terrestrial vegetation types for refinement usingaerial photography or ground surveys. A similar capac-ity does not yet exist for freshwater flora, and even themost sophisticated technology will not produce animage of how aquatic faunal communities are distrib-uted. To generate aquatic biological community mapsat a landscape scale, it may be feasible to overlay distri-bution maps of species or genera and to look for broadpatterns of similarity. However, with the exception ofthe best-surveyed parts of the world, there are at pres-ent no maps good enough for this kind of exercise.Because of these constraints, hydrological units –rather than species maps – tend to offer the mostworkable units to delineate freshwater ecoregions.

Drainage basins – also referred to as watersheds orcatchments – are the main hydrological and land-scape units of surface water systems. They also havestrong ecological relevance since their physiographicboundaries – except in rare cases – encompass thedispersal routes of species confined to fresh water.Through combining species distribution maps andphysical maps, it is possible to assess the degree ofbiological difference or similarity between neighbour-ing basins. Communities may be similar enough towarrant combining basins into a single, larger ecore-gion (for example, the Amazon River and FloodedForests ecoregion), while in other cases it may be nec-essary to split river basins to capture distinctive bio-logical differences. For example, in Papua New

Guinea, the special characteristics of Lakes Sentaniand Kutubu, relatively small lakes with endemic fauna,distinguish them from the surrounding New GuineaRivers and Streams ecoregion, a larger region coveringmost of the island.

In general, freshwater ecoregions are composed ofone or more ‘major’ basins, that is, those basinsdefined by the largest rivers of a region. An exampleof this would be the Yangtse Rivers and Lakes ecore-gion in China.1

5. The relationship between freshwater EcoregionConservation and Integrated River Basin Management

Integrated river basin management2 (IRBM) is anemerging approach to managing freshwater systemsfor sustainability. Like freshwater ecoregion conserva-tion, it is also fundamentally based on natural hydro-logical units, rather than on artificial political oradministrative regions. The emphasis of IRBM is onintegrated decision-making that takes into accountthe needs, expectations, activities, and basin-wideimpacts of sectoral stakeholders to ensure that watermanagement is economically, socially, and environ-mentally sustainable.

As part of its Living Waters Programme,WWF has devel-oped seven ‘Guiding Principles’ for effective IRBM, basedon the lessons learned from a range of case studiesthroughout the world. These Guiding Principles recog-nize that – until recently – IRBM has been a somewhattheoretical concept and one that has tended to focuson water quantity and quality issues. However, as expe-rience from practical application of IRBM begins toaccumulate, its potential as a key tool for biodiversityconservation has become clear, offering exciting oppor-tunities for synergy and ‘added value’ when ecoregionconservation and IRBM are combined.


1 Amazon River and Flooded Forests, Lake Sentani, Lake Kutubu, New Guinea Rivers and Streams, and Yangtse Rivers and Lakes are all Global 200 ecoregions.

2 Including the closely allied terminology of integrated catchment/watershed management.

WWF is therefore promoting and exemplifying goodpractice in both IRBM-led and ecoregion-ledapproaches to freshwater conservation in differentregions of the world. As highlighted below, eachapproach has its own distinguishing features, butthere are also many underlying similarities.

Key differences between IRBM and ecoregion conservation:

� Ecoregion conservation is primarily biodiversity-focused; IRBM often emphasizes sustainable landand water management that balances environ-mental and socio-economic elements. IRBMtherefore could incorporate or be based on ecore-gion conservation.

� Ecoregion conservation has primarily been appliedin areas of high-biodiversity importance, for exam-ple, the Global 200 Ecoregions. WWF believes thatIRBM can and should be applied to every majorriver basin in the world.

� Ecoregion conservation may or may not operate ata river basin scale, depending on the boundariesestablished for the specified freshwater ecoregion.Many priority freshwater ecoregions consist ofmore than one river basin. IRBM should alwayshave the physiographic and/or hydrological bound-aries of the river basin as its primary scale.

Key similarities between IRBM and ecoregion conservation:

� Both IRBM (as defined and advocated by WWF) andecoregion conservation are governed by a vision.

� Both IRBM and ecoregion conservation shouldspecifically incorporate biodiversity goals.

� Both should take account of the fact that landmanagement far away from a freshwater body canhave profound effects on its ecological processesand biodiversity.

� Both approaches should take account of the factthat threats originating upstream can affect biodi-versity (and indeed people) downstream.

� Both should therefore consider ways of maintainingand, where necessary, restoring water quantity,

water quality and physical structures/habitats, usingan ecosystem approach to whole drainage basins.

� Both should be underpinned by good science andeffective information flows.

� Both should incorporate active and informed com-munity and stakeholder participation.

In practice, this means that where an ecoregion’sboundaries coincide with those of a major river basin, acombined ecoregion conservation-IRBM approach candeliver biodiversity conservation through ensuring thesustainable management of freshwater resources andnatural functioning of the ecosystems that provideand regulate fresh water. In these circumstances themost pragmatic and cost-effective solution is to have asingle process for preparation of an integrated riverbasin management plan and an Ecoregion Action Plan.Furthermore, IRBM can be seen as a building block forachieving ecoregion biodiversity targets where theecoregion consists of more than one basin.

6. Key aspects of planning for freshwater biodiversityconservation and comparisons with terrestrial ecore-gion planning

While the removal of trees from a forested area mayhave little effect on the forest as a whole, the extrac-tion of water from a headwater stream may havemore significant impacts on freshwater ecosystemsdownstream. Ironically, the extraction of trees fromthe headwaters of a river basin may also have down-stream impacts on freshwater ecosystems, demon-strating the interlinkages between terrestrial andaquatic systems. Because the effects of disturbanceare felt downstream, a protected lake, wetland, or riverreach is only secure if threats originating upstreamare removed. Management of the entire basin istherefore essential to protect water quality and quan-tity, as well as physical structures and overall ecosys-tem functioning.

Other considerations that distinguish freshwater ERCare highlighted below:


� ‘Connectivity’ is essential to maintaining freshwaterbiodiversity. This includes connectivity betweenand within aquatic habitats (for example, betweenrivers and floodplains), and connectivity with sub-terranean systems. Loss of connectivity will funda-mentally alter both ecosystem processes andspecies distributions.

� Because humans depend on water sources andoften manipulate them, and because virtually allchanges to the terrestrial landscape affect aquaticsystems, very few freshwater ecoregions remainintact. For this reason, restoration is likely to be alarger component of freshwater ecoregion conserva-tion than it is in terrestrial ecoregion conservation.

� Minimum population sizes and/or minimum criticalarea requirements are only available for a fewfreshwater species. In addition, minimum habitatrequirements may be linear rather than areal inextent, and a species’ habitat needs may varyaccording to life stage or season. For example, inorder to breed, the Murray cod in Australia’s MurrayDarling Basin needs to be able to migrate in latespring and early summer when water levels arehigh and the water is warm. Over hundreds of kilo-metres of rivers, numbers of cod have crashed dueto barriers such as dams, cold water released fromthe bottom of dams, diversion of water for agricul-ture, and the release of water from dams at inap-propriate times of year.

� Perhaps the way in which freshwater ecoregionconservation departs most from the terrestrialapproach is through its focus on protecting andrestoring physical processes. Conserving flow pat-terns, water levels, and water quality will go far toprotecting freshwater biodiversity. This focuses lesson what to protect and more on how to protect it.That is, getting flow patterns and water quality‘right’ will contribute to the objectives of biodiver-sity conservation. At the same time, it is essentialto recognise that successful conservation of fresh-water biodiversity will also depend on the mainte-nance of natural physical structures and ecosystem

processes. Good water quantity and quality –though crucial – are not enough on their own.

� All projects differ, but the biological assessment ofa freshwater ecoregion should be structured prima-rily around the freshwater species, assemblages,and habitats that have identified the ecoregion as apriority, even if the ecoregion also contains excep-tional terrestrial biodiversity. This entails identify-ing the key habitats and processes that sustainimportant elements of freshwater biodiversity.Priority areas are those identified as requiring someform of conservation management, which could beanything from strict, year-round protection to selec-tive sustainable resource use.

By clearly defining both freshwater and terrestrialecoregions, and the differences between them, WWFhas diverged from other conservation organizationsthat are embarking on ecoregion conservation. Thedelineation of overlapping terrestrial and freshwaterecoregions generates a number of important ques-tions. These are addressed below.

Why separate freshwater and terrestrial ecoregions if allfreshwater habitats are part of terrestrial ecoregions?

� Neither the distribution patterns of many freshwa-ter species, nor the ecosystem processes that sustainthem, correspond well with terrestrial ecoregionboundaries. Defining terrestrial ecoregions alonecould therefore risk overlooking important elementsof freshwater biodiversity and lead to the develop-ment of ineffective conservation strategies. Forexample, the loss of part of a forest caused by thedamming and flooding of a river valley might haverelatively little adverse impact on the integrity of thesurrounding forest ecoregion. On the other hand,the effects of the dam on the corresponding fresh-water ecoregion might well be devastating, due, forexample, to the elimination of native fish popula-tions as a consequence of the physical barrier tomigration and changes in water temperature.


� Freshwater habitats and species also suffer fromadditional types of threat. While virtually all of thethreats that confront terrestrial ecosystems alsoaffect freshwater systems, the opposite is not nec-essarily true. For example, conversion of forests foragriculture or timber production can influencedownstream freshwater habitats through increasedsedimentation, greater chemical pollution, alteredwater temperatures, increased runoff, anddecreased organic matter inputs. On the otherhand, construction of an instream impoundment ora channelization project may affect nearby terres-trial habitats, but most of the terrestrial landscapewithin the basin is likely to be relatively unaffected.Exclusively freshwater species may also be less ablethan terrestrial fauna to escape threats such asinvasive exotic species or pollution.

Should a freshwater Ecoregion Action Plan focus exclu-sively on freshwater biodiversity and habitats? Wheredoes the wider basin fit in?

� The identification of priority areas is only one stepof a process that should include a biological assess-ment and development of a biodiversity vision (seesection 7 below). Many of the critical processesthat maintain freshwater biodiversity are linked toprotection of the wider basin, and many of thethreats to biodiversity also originate within thebasin. For example, maintenance of water levelsand flows, critical for most freshwater organisms,depends largely on surface and subsurface flowsacross the basin, and these in turn are heavilyaffected by land use.

How is biodiversity assessed when priority freshwater andterrestrial ecoregions overlap? Are there inherent conflicts?

� Priority freshwater and terrestrial ecoregions oftenoverlap. Where such overlap occurs, it is stronglyrecommended that the biological assessments andvision development are combined. This is impor-

tant to maximize the synergies between, for exam-ple, forest or grassland conservation on one hand,and freshwater conservation objectives on theother. Joint ‘vision’ development is important toensure that freshwater priorities are not inadver-tently overlooked and that planning resources areused as efficiently as possible.

� The degree to which terrestrial and freshwaterecoregions match each other both geographicallyand ecologically will largely determine the extentto which the visioning processes are combined. Ifone ecoregion completely subsumes the other, thelarger ecoregion can define the area of concern. Ifthe two ecoregions overlap only in part, the deci-sion is more complex and should be based on bio-logical criteria. Both ecoregions may be taken intheir entirety, or the boundaries may be modified tomake the process more feasible. If the decision ismade to alter the boundaries of ecoregions, careshould be taken to ensure that biodiversity conser-vation strategies do not suffer as a consequence.

� Invariably, one of the main threats tocoastal/marine ecoregions is land-based pollution,with rivers and streams acting as vectors. In thesesituations, conservation activities in thecoastal/marine ecoregion should be integrated withthe freshwater ecoregion approach to maximizeconservation of both freshwater andcoastal/marine biodiversity.

What is the approach for ‘terrestrial’ ecoregions thatare defined largely by wetlands such as flooded forestsor flooded savannahs?

� The category to which an ecoregion has beenassigned is less important than the biodiversity fea-tures that distinguish it as a conservation priorityand the insight employed during the planningprocess. At the most fundamental level, a freshwa-ter approach to ecoregion planning will be neces-sary wherever hydrological processes are critical forsustaining biodiversity.



Will the existence of separate terrestrial and freshwa-ter ecoregions confuse policy-makers and make conser-vation more difficult?

� The ecoregion concept and that of ecoregion con-servation can be difficult to understand at first, andintroducing two (or three, if coastal/marine areincluded) sets of ecoregions and priority areaswould doubtless be confusing to many people,including policy-makers. For this reason, it is proba-bly wise to combine priority areas where possible,to present a unified vision to all stakeholders, andto emphasize the links between the freshwater andterrestrial realms. Even if separate freshwater andterrestrial analyses produce different strategies, asingle biodiversity vision can encompass both.Theoretically, it should be easier to persuade a pol-icy-maker to commit to an action that conservesboth terrestrial and freshwater biodiversity featuressimultaneously. The process by which priorities arechosen should be transparent and carefully docu-mented, but in most cases people will be less con-cerned with how priorities are chosen, than whythey are chosen.

7. An overview of the vision-building process

The key feature of ecoregion conservation is the cleararticulation of a biodiversity vision that incorporatesthe full range of biological features. A biodiversityvision is essential because it helps to move beyond a‘business-as-usual’ approach to the actions actuallyrequired for effective conservation. It serves as atouchstone to ensure that the biologically and ecolog-ically important features remain the core conservationtargets throughout the ecoregion conservationprocess. Even when responding to local emergenciesin the course of developing an ecoregion programme,a biodiversity vision provides a useful framework forinterpreting threats to the integrity of the entireecoregion rather than to individual sites. Without avision, the overarching conservation targets may belost, there may be difficulty in establishing priorities,and scarce resources could be wasted.

Contributors to the ecoregion planning process will beable to participate most effectively if they understandhow their work fits into the larger vision-buildingprocess. The Terrestrial Workbook presents a flowchartof the steps involved in defining priority areas anddeveloping a biodiversity vision for a terrestrial ecore-gion. These basic steps hold true for freshwater ecore-gions also, but experience suggests that there is roomin freshwater projects for greater flexibility in thesequence of steps, the process of carrying them out,and the final outputs.

A freshwater-oriented flowchart is presented here as asuggested framework only, not as a prescription. Eachecoregion will require a somewhat different approach,based on the types and sizes of habitats, the kindsand quality of available information, and the currentand future threats to biodiversity. For a clear andunambiguous biodiversity vision to emerge, all partici-pants in the process should understand and agree ona standard approach before they begin their work.

8. Key issues for conducting biological assessments infreshwater ecoregions

Knowing the original distribution of native vegetationcommunities in a freshwater ecoregion is often not as crit-ical as knowing about the distribution of aquatic habitats

In some cases, aquatic or riparian vegetation may beprimary determinants of aquatic habitats, but this isnot always the situation. The physical characteristics ofaquatic systems (for example, substrate, water chem-istry, flow regime, temperature) are always importantdeterminants of aquatic habitats, whereas the contribu-tion of associated vegetation varies. It is also importantto recognize that aquatic and riparian vegetation isusually itself determined by physical characteristics. Ifthe outstanding biological features of a given freshwa-ter ecoregion are related to vegetation (for example, fora flooded forest ecoregion), it makes sense to map thedistribution of vegetation communities to the bestextent possible. In other cases, it may be more impor-tant to try to map the distribution of aquatic habitat

Biological importanceStep 1. Revisit ecoregion boundaries, using collected information and expertiseStep 2. Refine biogeographical subregions Step 3. Revisit habitat types, focal elements, and minimum requirementsStep 4. Select candidate priority areasStep 5. Synthesize multiple types or layers of candidate priority areas, if necessaryStep 6. List component habitat types for candidate priority areasStep 7. Conduct representation analysisStep 8. Analyze set of candidate priority areas to determine if all focal elements, and the

minimum requirements for maintaining them, have been addressedStep 9. Assess biological importance of candidate priority areas

Ecological integrity Step 1. Evaluate habitat intactness of candidate priority areasStep 2. Evaluate population/species viability of areas, add or change boundaries if necessaryStep 3. Assess ecological integrity of candidate priority areas

Prioritizing areas at the ecoregion scaleStep 1. Assign priority levels to candidate areas using integration matrix/algorithmStep 2. Conduct representation analysis again, and elevate the priority level of one or more

areas if necessaryStep 3. Analyze portfolio of priority areas to determine if conservation targets have been

addressed, and elevate the priority level of one or more areas if necessaryStep 4. Analyze overlap of priority areas with protected areas, and with results of other pri-

ority-setting exercises

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Identifying specific and overarching future threatsStep 1. Identify future threats specific to priority areas, and the intensity of those threatsStep 2. Identify overarching threats to the region, ecoregion, and subregions, and their intensityStep 3. Identify specific actions or kinds of conservation required for each priority area, sub-

region, or larger areas, and the urgency of action

Developing a biodiversity visionStep 1. Evaluate if priority areas and actions, taken together, would result in the long-term main-

tenance of the ecoregion’s conservation targets, and add new priorities if necessaryStep 2. Synthesize key information gaps and research prioritiesStep 3. Combine priority areas map and priority actions into comprehensive visionStep 4. Draft a vision statementStep 5. Identify next steps

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types based on their physical characteristics, or to mapareas that are known to be critical for maintaining iden-tified conservation targets.

For many freshwater ecoregions only anecdotal informa-tion exists on the demography of potential focal species

With the exception of certain mammals, colonial water-birds, and commercially important fish, the demogra-phy of the majority of target species is likely to be virtu-ally unknown. One task of the ecoregion team is toidentify critical research gaps. In many cases, under-standing the life histories of focal species is moreimportant than charting the demographics of theirpopulations. Although many aquatic taxa are poorlystudied, lotic (flowing water) species often have specifichabitat requirements at different stages of their lifecycle, such as spawning and juvenile rearing. The sameis true for some lake species, particularly those thatmigrate up rivers to spawn. Identifying habitats thatare critical to the survival of key species, and determin-ing the minimum quality and extent of those habitatswhere possible, may be essential lines of investigation.

Considering physical processes, and particularly thenatural hydrologic regime, is of critical importance

It is vital to understand, to the best extent possible,what constitutes the natural hydrologic regime (includ-ing the geographic and temporal scales over which itoperates), how it maintains different aquatic habitats,how freshwater taxa are adapted to that regime, andwhat the main threats are to its maintenance.Consideration should also be given to identifying mini-mum targets (for example, minimum flows, minimumnumber of days of flooding, minimum lake levels) andapproaches for achieving them. It may be far easier todevelop a plan for meeting such targets in impoundedor otherwise engineered systems despite theirdegraded state. In freshwater systems without flow-regulating structures, maintaining natural hydrologicalvariability is crucial. For this reason, the inclusion ofhydrologists in the freshwater project team is essential.

Understanding biodiversity patterns

In a typical biological assessment, one of the first stepsis mapping areas that are important for achieving theconservation targets of the ecoregion, (see page 4):

In most ecoregions, identifying areas supporting thesefeatures will be a challenge because of a lack of data.Even in the best-studied ecoregions, an element ofeducated guesswork is required to identify areas ofbiodiversity importance because the life histories ofmost freshwater species are poorly known. Withinsufficient data, proxies can provide guidance forwhich areas may be the most important for biodiver-sity conservation. Some examples of proxies are:

� Older habitats – those that have not been ‘re-shaped’ by glaciation or tectonic events in therecent past – may contain endemic species, thoughsome species radiations occur in ‘new’ habitats.Isolated habitats may also have a higher degree ofendemism, although they may have fewer speciesbecause of fewer opportunities for colonization.

� Areas characterized by sinkholes, caves, and under-ground drainage may contain rare cave-dwellingspecies, or species adapted to spring outflows.These species can include fish, amphibians, and awide range of invertebrates, which often havehighly restricted ranges.

� Waterfalls often serve as effective barriers in loticsystems, with different biotas found above andbelow them. Large rivers may also serve as barriersto tributary biotas.

� Temperature is one of the primary factors deter-mining the distribution of freshwater fish in thetemperate zone. Although water temperature isstrongly influenced by shade, groundwater inputs,flow, and water transparency, climate will be themain determinant of water temperature at theecoregion scale. For ecoregions spanning large lati-tudinal or altitudinal ranges, climatic isothermsmay give general information on distributions offish species.


� High levels of habitat heterogeneity (complexity)are associated with hotspots of freshwater biodi-versity, particularly in river systems. Dynamic areaswhere habitats are naturally created and destroyedmay be important as priorities.

� Habitats subject to different flooding regimes (tim-ing, duration, and levels) are likely to harbour differ-ent biotas. Some information on flooding may bederived from remotely sensed images.

� Information from geological and soil surveys may alsoyield information that can be used as a proxy for bio-logical data. For example, in limestone areas, perma-nent surface water habitats are likely to be scarce.

Working at practical scales

Most freshwater ecoregions – indeed, most ecoregionsin general – are so large that it can be difficult to con-ceptualize how to conserve biodiversity. Conducting abiological assessment at the scale of an ecoregion, anddeveloping a vision from the results of that assess-ment, ensures that large-scale biodiversity patternsand processes are taken into account and priority unitsfor more focused work are identified. Subsequent pri-oritization as part of an implementation plan mightcomprise work at several scales, such as:

� Local site- or species-specific field projects that areboth strategic and high profile, enabling EcoregionAction Plans to achieve quick successes for buildingcredibility and support;

� Sub-basin field and policy projects that demonstratemedium- to long-term solutions to major threats tospecies, assemblages or ecological processes;

� Basin-scale policy solutions that draw on field expe-rience to put in place the legislation and mecha-nisms needed for long-term conservation.

Giving priority consideration to different ecosystem types

Upstream sub-basins are more likely to be intact andeasier to protect from future disturbance. Protection ofheadwater basins is critical for the maintenance ofdownstream flow regimes and water quality.

Headwater habitats also support species not founddownstream and are the destinations of many migra-tory fish and other aquatic fauna. For these reasons, theinclusion of headwater sub-basins in any conservationportfolio is recommended. However, to capture the fullcomplement of an ecoregion’s freshwater species and tomaintain linked upstream-downstream processes,downstream areas must also be included. This is partic-ularly important for some anadromous fish, such assalmonids, which migrate through downstream watersto reach rearing grounds. Downstream areas are gener-ally more accessible, have more abundant waterresources, are more productive, have greater species rich-ness, and tend to be subject to a greater intensity ofhuman use. Conservation of downstream freshwaterhabitats may require more creative approaches, includ-ing a greater emphasis on restoration or rehabilitation.Conservation of intact upstream sub-basins should bematched by efforts to conserve more disturbed and bio-logically rich lowland freshwater habitats.

The importance of refugia and maintaining connectivity

Studies suggest that a key element in the persistenceof freshwater biota, at least for riverine systems, is thepresence of refugia (habitats or environmental factorsthat convey spatial and temporal resistance and/orresilience to biotic communities affected by biophysi-cal disturbances). Refugia are particularly importantfor freshwater ecoregions containing a predominanceof disturbed habitats as a result of human activity.

Refugia appear to be critical for the persistence ofmetapopulations (partially isolated populationsbelonging to the same species). Studies of the recov-ery of riverine populations following disturbancestrongly suggest that many aquatic species havemaintained their historical distributions through theprocess of recolonization following local extinction.Human activities not only create disturbances (andlocal population extinctions), but also serve to destroyboth refugia and connections among habitats thatwould otherwise permit recolonization.

Specialized ecoregion terminology and definitions:

The WWF Sourcebook for Freshwater Ecoregions provides a comprehensive introduction to the specialized termi-nology used in ecoregion conservation.

For further information, please contact:

Publication Credits:

Authors: Robin Abell, Michele Thieme, Eric Dinerstein, and David OlsonPublication Manager: Robin AbellEditor: GrammariansDesign: 202design

Please cite this publication as: Abell, R., M. Thieme, E. Dinerstein, and D. Olson. 2002. An information papersummarizing WWF’s A Sourcebook for Conducting Biological Assessments and Developing Biodiversity Visions forEcoregion Conservation. Volume II: Freshwater Ecoregions. World Wildlife Fund, Washington, DC, USA.

Acknowledgments:

We would like to acknowledge the many individuals who assisted in the completion of this sourcebook. JamiePittock, Gordon Orians, Curt Freese, and George Powell helped to shape the focus of this document with theirimportant reviews of drafts. Representatives from WWF-Peru and WWF-Brazil permitted us to use the prelimi-nary results of the Amazon River and Flooded Forests assessment to illustrate a suggested approach, and GISspecialists from the Conservation Science Program provided additional maps as well as information on GIS andsatellite imagery. Numerous authors and publishers gave permission for the use of excerpts, which enrich thissourcebook immeasurably. This sourcebook is modeled on a prior volume about terrestrial ecoregions and bor-rows many ideas from it. Many people throughout the WWF network provided encouragement for this source-book, and we particularly want to thank Diane Wood, Judy Oglethorpe, and David Sandalow. We are especiallythankful to Kimberley Marchant, who helped guide this volume to production. WWF gratefully acknowledgesUSAID for its support of this publication.

WWF-US Conservation Science Program:[email protected]

WWF Living Waters Programme:[email protected]

Global 200 Ecoregions information:http://www.wwfus.org/global200/spaces.cfm

WWF staff can also download information from theecoregion and Living Waters pages of the WWF Intranet.

WWF’s mission is to stop the degradation of the planet's natural environment and to build a future inwhich humans live in harmony with nature by:

� conserving the world's biological diversity

� ensuring that the use of renewable natural resources is sustainable

� promoting the reduction of pollution and wasteful consumption

advancing the conservation of freshwater biodiversity through...

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