125

Diversity of Wetland Ecosystems — Integrating Multiple
Spatio-temporal Scales for Coherent Conservation Strategies
Stefan HOTES
Department of Animal Ecology, Justus-Liebig-University,
35392 Giessen, Germany
e-mail: stefan.hotes@bio.uni-giessen.de

Abstract
Biological diversity, its evolution and functions are a matter of debate in scientific as well as politicalcontexts. The variability of biological units can be studied across a range of spatial and temporal scales, e.g.
from individuals to populations, communities and whole ecosystems, and their dynamics can be followed
over “ecological,” “evolutionary” or “geological” time periods. Knowledge gained from studies at any ofthese levels of complexity can be relevant for decision-making in nature conservation or restoration,although actual projects often rely solely on data related to abundance and distribution of selected taxa collected during short-term surveys. In this paper it is demonstrated how insights concerning organismic andenvironmental variability on different spatial and temporal scales can be combined to develop a comprehensive framework for conservation and restoration of ecosystems, using wetlands in Japan and Europe as an
example.
Key words: Europe, Japan, nature conservation, nature restoration, wetlands

1. Introduction
The diversity of life on earth is essential for humanwell-being, and it is widely agreed that it also has value
in its own right (Millennium Ecosystem Assessment,
2005a). However, socioeconomic change during the last
decades has led to a rapid increase of natural resource
consumption, alteration of land use practices and as aconsequence to a widespread decline of biological diversity. Within the framework of the UN Convention on
Biological Diversity, three levels of biological diversity
are recognized: the genetic level, the species level andthe ecosystem level. In theory, biological diversity at the
species level will be maintained if speciation and extinction are balanced. This requires that ecological processes
like trophic interactions (fluxes of energy and matter),gene flow (pollination, dispersal of individuals) and “appropriate” disturbance regimes function. At the level ofcommunities or ecosystems there is currently no generally accepted theory analogous to evolutionary theory fororganisms that explains their emergence and disappearance. Starting from the debates of the early 20th century
on the “nature” of plant communities that centered aroundquestions of deterministic development versus random
combinations of “whatever is available,” new approaches
have developed that try to bridge the gap between theextremes and explain the observations of both deterministic and stochastic behaviour (Lortie et al., 2004).
Global Environmental Research
11: 125-134 (2007)
printed in Japan

Much of the motivation for the current efforts to prevent a further decline of biodiversity stems from therecognition that ecosystems are the basis for all human
livelihoods through the provision of ecosystem services.
This encompasses both natural ecosystems that are notactively managed and cultural ecosystems that havedeveloped through human land use.
Humans have altered ecosystems for millennia inorder to increase the yield of food and other natural resources. The cultural landscapes that developed throughthese activities are often highly diverse and have now
become the target of “nature” conservation as intensification of land use is threatening their existence. The
importance of the protection of heterogeneous ecosystems from conversion to uniform industrial systems has
been recognized early on in the nature conservation
movement, although it initially had hardly any effect onpolitical decisions (Bramwell, 1989; Kuwako, 1999;
Stiftung Naturschutzgeschichte, 2003). Nowadays, thisknowledge is increasingly becoming part of public policy, and governments have started promoting not only
the protection of remnant ecosystems where populationsof rare or threatened plant and animal taxa persist, butalso the restoration of different types of ecosystems(Thauront et al., 2003). In addition to aesthetic considerations (beauty of landscapes) and “biocentric”
arguments that acknowledge the value of non-humanlife in its own right, economic reorganization, demo©2007 AIRIES126

S. HOTES

graphic trends and disaster prevention have become partof the driving forces. Restoration is seen as a tool tosolve multiple problems simultaneously. This poses a
new challenge to planners who have to decide where
and how to carry out these measures, which requires anunprecedented amount of knowledge on different aspects of the environment and its interactions with society. Information on the current distribution and abundance of species and ecosystems as well as data on pastconditions are needed in order to derive models of how
their long-term dynamics work. Socioeconomic conditions also have to be documented as they have become amajor factor shaping landscapes and biota. Using “spatial” and “temporal” aspects of ecosystems as the basic
ordering principle I will discuss global and regional
issues concerning wetlands, their ecology, classification,conservation and restoration with a focus on the situation in Europe and Japan.

2. Spatial Aspects of Wetland Biodiversity
Depending on the spatial scale of observation, different features can be distinguished in ecosystems. This
simple fact has important implications for ecologicalscience as well as for ecological restoration. It determines whether a certain area is perceived as being
homogenous or heterogeneous, whether the entire distribution range of a species or ecosystem can be coveredor whether only the area that one individual may need tofulfill its life cycle can be dealt with, etc. In the context
of ecological restoration it is important to note that thesize, shape and internal structure of a site that is chosen
for restoration measures have influence on the numberof species that can be expected and on ecological functions (e.g. hydrological functions, source-sink functions
for chemical compounds) that it may develop. In thissection I will move from a brief description of global
patterns to regional and local patterns found in European
and Japanese wetlands.
2.1 The global scale
Wetlands are part of all biomes, and although theyoften make up only a small proportion of the total surface area, they account for much of the productivity andprovide essential ecosystem services (Millennium Ecosystem Assessment, 2005b). Overviews of importantfeatures that apply to wetlands in general and descriptions of wetlands in different geographical regions havebeen given in a number of monographs and textbooks(Gore, 1983; Mitsch & Gosselink, 2000; Wigham, 1993).
The most comprehensive definition of “wetland” incurrent usage is the one used by the Ramsar Convention(1971): Article 1.1. provides that “wetlands are areas ofmarsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or
flowing, fresh, brackish or salt, including areas ofmarine water the depth of which at low tide does notexceed six metres.” Article 2.1. adds that wetlands “mayincorporate riparian and coastal zones adjacent to thewetlands, and islands or bodies of marine water deeper
than six metres at low tide lying within the wetlands”(Ramsar Convention COP8, 2002). It thus covers all
wetland ecosystems found on the continents and includes shallow marine areas. Although these areas havein common that they are in some way characterized by
the presence of water at least temporarily, they differ
vastly in their ecological conditions.
In order to systematically plan the conservation andrestoration of these ecosystems (as is true for any object
that is to be dealt with in planning), three types of information are needed: 1. Understanding of the variables
that influence the ecosystems (“how do the ecosystems
function”); 2. Knowledge of the current distribution of
the ecosystems (“where are the ecosystems located andhow large are they”); 3. Knowledge of the rate ofchange (“how much of which ecosystem type was there
in the past”). The need for this information is selfevident, and a lot of progress concerning the understanding of ecosystem functioning has been made by the
combined efforts of scientists in disciplines like plant
and animal ecology, limnology, hydrology, geomorphology, climatology etc. However, even today science isstruggling to correctly predict the way ecosystems willreact to changes of certain variables, which is due tophenomena that are common to all complex anddynamic systems: a large number of variables are interacting through positive or negative feedback cycles,
making it difficult to decide on the relative importanceof a certain factor. Furthermore, changes are often
non-linear, i.e. reaction norms are not constant along
gradients, which means that under certain (generally
unknown) circumstances small changes in one variable
can cause large changes in another (Folke et al., 2004;
Scheffer & Carpenter, 2003). In addition, stochastic
events can influence ecosystems, and the impact of such
events can persist for long periods of time, although thefact that such an event happened may be hard to detect.
Knowledge of the distribution of wetland ecosystem
types and of their rates of change is improving, especially as remote sensing techniques develop and become
more widely available (Davidson & Finlayson, 2007;
Rosenqvist et al., 2007). However, in spite of this progress fundamental questions of “how much of which
wetland type is located where?” and “how have theychanged through time?” are still not sufficiently answered. The data are fragmentary even in the best-studied regions, differences in recording schemes make it
difficult to bring together data from different sources,
and remote sensing techniques are not yet established ina way that would make relevant information easily
accessible for decision-makers (Finlayson & Spiers,
1999).
The global distribution of wetlands is determined byhydrological processes and therefore reflects large-scalepatterns of climate (precipitation, evapotranspiration),
geology and geomorphology. The largest wetland areas
are located in the mid to high latitudes of the northernhemisphere, and the humid tropics, subtropics as well as

Conservation of Wetland Ecosystem Diversity

the mid-latitudes of the southern hemisphere also contain considerable wetland areas (Finlayson & Spiers,
1999). In addition to these zones with often continuous
wetland ecosystems, smaller wetlands with a more scattered distribution and/or only temporary water supply
exist even in arid regions. Large wetlands generally develop in areas with low relief energy which are usuallyfound at low altitudes, and mountain regions mostly
have smaller wetlands that show different ecologicalcharacteristics than those in the lowlands. However,mountainous areas generally experience higher precipitation than lowlands, and they can be important for thehydrological functioning of wetlands in low-lying areasthat receive their water supply from mountain ranges,
often over long distances.
In order to maintain the whole range of types of wetlands defined by the Ramsar Convention, it is necessary
to also consider smaller wetlands with a scattered distribution and even temporary wetlands that are not continuously “wet.” Recognizing such wetlands in surveys
is a technical challenge as they are not easily distinguished by remote sensing. Current satellite-borne remote-sensing platforms offer either a broad spectral
bandwidth or high spatial resolution, but for the delineation of wetland units and their catchment areas a combination of both is needed, including a sufficiently hightemporal resolution.
Several survey projects are being undertaken by the
Ramsar Convention secretariat in collaboration withgovernment bodies, NGOs and private companies that
aim to improve the spatial and temporal accuracy of
global wetland monitoring, but the estimates of wetlandarea and wetland quality are still imprecise. Estimates of
wetland areas globally published before 1999 ranged
from 560,000,000 to 970,000,000 ha. Based on a compilation of survey data in the “Global review of wetland
resources and priorities for wetland inventory”(Finlayson & Spiers, 1999) the minimum estimates werecorrected to 1,275,847,000-1,279,211,000 ha (Table 1).
However, these much higher figures are not always usedby officials dealing with wetland conservation, e.g. inthe most recent publication of the European Union on
wetlands an estimate of 570,000,000 ha is quoted (Silva
et al., 2007).
One major problem for collating information fromdifferent sources is the lack of coherent criteria forclassification. Differences in classification systems anda lack of clear definitions of the units used cause
ambiguity that is multiplied when data from different
surveys are combined (Finlayson & van der Valk, 1995;
Hotes, 2007).
Published cartographic sources showing the global
distribution of wetlands include e.g. the map of Gore(1983, reproduced in (Williams, 1990)) that gives arough classification of land surfaces into > 10% wetland
cover, > 0.5% wetland cover and < 0.5% wetland cover,and distribution maps of dominant soil types have also
be used as an aid for identifying major wetland areas(Fig. 1; United States Department of Agriculture

127(USDA), 2003). The International Water Management
Institute is developing an interactive map that shows the
distribution of important wetland sites worldwide thatcurrently (January 2008) allows access to basic
information on wetlands in Asia, Africa, Oceania andSouth America (International Water Management
Institute, 2007).
Although the rate of wetland loss seems to haveslowed down in some industrialized countries (Fujita
et al., 2007; Silva et al., 2007), wetland reclamation forindustry, agriculture or housing continues to put enormous pressure on wetlands worldwide. This pressure isexacerbated by ongoing climate change and changes inagricultural practice (e.g. conversion of rice production
from flooded paddies to dry field farming) which areoften connected to changing patterns of precipitation,
evapotranspiration and run-off (Tuong et al., 2005).
Priority areas for wetland conservation should belocated where ecosystems are left in a good state, i.e.
where functioning units including an intact catchment
area can be found. Areas for restoration, on the other
hand, must be those where due to human influencedegradation or destruction have occurred. The available
resources for conservation and restoration should be
used as efficiently as possible, and this would mean thatmost should be invested in biodiversity hotspots if species numbers are considered to be the most importantcriterion. However, other ecosystems with lower species
numbers can be more relevant in terms of ecosystem
functions and ecosystem services, e.g. carbon sequestration. There is currently no scientific basis on which general decisions concerning the relative importance(“value” for human societies) of biodiversity per se or ofcertain ecosystem services can be founded. Therefore, it
is not possible to give scientifically sound recommendations on how resources for conservation and restoration
Table 1 Estimates of global wetland areas in the “Global
review of wetland resources and priorities for wetland
inventory” (Finayson & Spiers, 1999). The large differences in the figures reflect gaps in the knowledge of
wetland distribution as well as inconsistencies in thewetland classification systems of the data sources.
Wetland types and survey regions
Area (ha)Natural freshwater wetlands
570,000,000
Rice paddy
130,000,000
Mangroves
18,100,000
Coral reefs
30-60,000,000
Total wetland types excluding e.g.
saltmarshes and coastal flats,
748,100,000- 778,100,000
seagrass meadows, karsts andcaves and reservoirs
Africa121,322,000- 124,686,000
Asia
204,245,000
Eastern Europe
229,217,000
Neotropics
414,917,000
North America
241,574,000
Oceania
35,750,000
Western Europe
28,822,000
Total wetlands (sum of areas in
1,275,847,000-1,279,211,000
survey regions)

128

S. HOTES

Fig. 1 Global wetland distribution map by the USDA (2003) based on the FAO-UNESCO soil map of the world and the
USDA-NRCS soil climate map. Six categories (upland, lowland, organic, salt affected, permafrost affected, inland water
bodies) are distinguished.

should be distributed on a global scale, although theMillennium Ecosystem Assessment provides a first attempt in this direction (Millennium Ecosystem Assessment, 2005c). Based on estimates of wetland loss during
the 20th century, the greatest decline of wetland areas
has occurred in those countries with the highest degreeof industrialization, i.e. Europe, North America andJapan (Finlayson & Spiers, 1999). These therefore havethe highest need for restoration measures, whereas inless industrialized regions there are relatively more
options left for maintaining existing wetland ecosystems,
i.e. for conservation measures.
The Ramsar Convention, the Ramsar wetlands database and the associated activities of government bodies
and NGOs form a framework in which many of theexisting problems for wetland conservation and restoration can be addressed. What becomes clear from theabove, though, is that there are large gaps in the knowledge of wetlands on a global scale. In order to collectnecessary data on wetland distribution, trends in wetlandarea and wetland quality across large areas according toa standardized protocol, internet-based techniques areimportant supporting tools. Remote-sensing and groundsurveys need to be combined as the interpretation ofdata collected by sensors requires adequate checks of
their accuracy. Whether these monitoring efforts will
create the desired information depends largely on thewill of governments to fund the activities. The fundamental scientific problems concerning the prediction of
ecosystem responses to external impacts or management,
however, are difficult to solve, as methods that try tocope with the enormous complexity of the systems
under consideration are still new, and the lack ofreplicability in ecosystem-scale experiments prevents
the use of established statistical methods (Blackburn,2004).
2.2 The regional scale
Global strategies for wetland conservation necessarily neglect details that can only be considered when thefocus is placed on a smaller area. Relatively large
amounts of data have been compiled on wetlands in
Europe and Japan, creating comparatively detailed insights into their distribution and functioning. However,the following sections will demonstrate that even here
the available information is far from sufficient for thedevelopment of scientifically sound wetland restoration
targets.
2.2.1 Wetlands in Europe
Europe as a geographical entity covers about
10,180,000 km2 and stretches from the Mediterranean tothe arctic climate zone. According to the KoeppenGeiger climate classification, nine different categories
occur in this area (Peel et al., 2007). Climatic variationin combination with geographical and biological features is used to deduce a basic subdivision of Europe
into nine biogeographical regions (Fig. 2; European
Environment Agency, 2007). The boundaries of theclassical peatland zones of Moore and Bellamy (1974)
coincide approximately with some of the boundaries ofthe biogeographical regions, reflecting the influence ofthe same climatic and geographical factors in both

Conservation of Wetland Ecosystem Diversity

schemes. Further biogeographical subdivisions havebeen developed at national and sub-national levels.
Biogeographical or “ecoregions” are useful for theidentification of large-scale discontinuities in environmental gradients and provide a basic scheme that canhelp to define biodiversity at the ecosystem level.
However, actual conservation activities including thedesignation and management of protected areas needsmaller units. In the European Union, the CORINE biotopes project first developed such a system in the 1980s(Moss et al., 1991). Based on this, the habitat classification system for the European Habitats Directive(Council of the European Community, 1992) was established. The list includes only such habitat types that areconsidered “relevant at the European level,” i.e. it does
not attempt to give a comprehensive overview of all
types that exist in the region. In its current version, it
includes 231 habitat types, 71 of which correspond at
least partly to wetlands (European Commission DG
Environment, 2007).
Although the system of the Habitats Directive is now
well established and in use by agencies and planners
throughout the European Union, it is not free of controversies, and wetland ecosystems provide an example forthis. There has been a long debate on the most appropriate way of dividing wetland ecosystem types that is
exemplified by the discussion on mire classification andterminology (Bragg & Lindsay, 2003; Gore, 1983;
Moore & Bellamy, 1974; Sjörs, 1985; Wheeler &Proctor, 2000). The spatial scale of observation and the129criteria on which the separation of types are based determine what can be distinguished, and these parameterschange according to the purpose of a particular classification scheme. Problems regularly occur where certain
habitat types of the same hierarchical level exist in close
proximity or form mosaics. Treating these separately
does not make sense in ecological terms as they often
form functional units, but for administrative purposes
exact definitions and delineations have to be given. In
some wetland types delineation and subdivision are
more straightforward as for example in open water
bodies (rivers, lakes, oceans) where the shoreline (andits seasonal variation) provide more obvious criteria, or
where steep gradients of key environmental factors
create sharp boundaries (e.g. salinity). Because of the
difficulties of finding a unified approach to classification, the Interpretation Manual of European Habitats
lists a number of regional classifications (UK, French,
German, “Nordic” (Scandinavian) etc.) in cases where
the distribution range of a type is large and has different
names under different systems (European Commission
DG Environment, 2007). Definitions are mostly basedon vegetation cover with additional criteria for types
where plants are scarce, and bibliographic references forrelevant publications are given. The habitat types chosen
for inclusion in the list of the Habitats Directive are
primarily such that are considered “natural,” but theinterpretation manual also indicates where land use hascreated certain types.

Fig. 2 Map of the biogeographical regions of Europe.
(European Environment Agency, 2007)

130

S. HOTES

2.2.2 Wetlands in Japan
Japan, although it is much smaller (378,000 km2) insurface area than the European subcontinent, extends
over four of the climatic zones in the Koeppen-Geiger
system (Peel et al., 2007) and has steep altitudinal gradients that create a wide range of environmental conditions. Biogeographical subdivisions in Japan havetraditionally been based on boundaries in the distribution of plant and animal taxa represented by “lines” thatmostly run between different islands of the archipelago
or along distinct geographical structures within islands(Takeuchi et al., 1980). Further work on the classification of land areas was carried out in connection withphytosociological surveys of Japan. Detailed vegetation
maps have been compiled and updated several times forthe whole country (Ministry of the Environment, 1992),
and summaries providing an overview of the latitudinal
and altitudinal distribution of vegetation zones havebeen published (Numata, 1974). However, the basic
subdivision into regions in the context of vegetation
classification or wetland surveys has been based on
historical administrative units that only partly reflectnatural boundaries (Ministry of the Environment, 2001).
Biogeographical regions defined by a set of climate,geology, soil and vegetation parameters comparable tothose used in Europe have been developed only recently
in the context of the National Biodiversity Strategy ofJapan (Fig. 3; Ministry of the Environment, 2007).
Probably the first attempt to estimate the distributionof a certain wetland type in Japan was the work on peatlands by Sakaguchi (1961, 1979). He used topographicalFig. 3 “Regional subdivision for the conservation of biodiversity” in Japan (Ministry of the Environment, 2007),in effect a biogeographical subdivision of the Japanesearchipelago. The ten regions distinguished are: 1. Eastern
Hokkaido; 2. Western Hokkaido; 3. Pacific side of northcentral Honshu; 4. Sea of Japan side of north central
Honshu; 5. Hokuriku-San’in; 6. Pacific side of central
Honshu; 7. Setonaikai (Inland sea area); 8. Kii Peninsula,
Pacific side of Shikoku, Kyushu; 9. Ryukyu Island
chain; 10. Ogasawara Islands.

and soil maps to delineate areas with peat deposits,
irrespective of their current land cover.
Wetland surveys from a nature conservation perspective were first conducted with a focus on areas important for birds (IWRB Japan Committee, 1989; Scott,1989). A comprehensive overview of lakes, marshes andmires was attempted in a survey by the Geographical
Survey Institute of Japan based on the analysis of maps,
earlier surveys of “outstanding natural areas” and otherpublished sources (Geographical Survey Institute, 1994).
This list included 451 lakes over 1 ha in size and 438“wetlands”, mostly those that are indicated on 1:50000
topographical maps, but smaller areas were included if
published sources were available. Area size is indicatedfor lakes (possibly only the area of open water surfaces),but for “wetlands” only a broad categorization into fourclasses is given: A: >10 km2, B: 1-10 km2, C: 0.5-1 km2,
D: <0.5 km2. It is reasonable to assume that the area islargest in Hokkaido where extensive mires remain in thelowlands. The only other large wetland area indicated on
the distribution map of wetlands in Japan are the tidal
flats in Ariake bay in Kyushu.
The “List of 500 important wetlands of Japan”(Ministry of the Environment, 2001) largely follows thiscompilation. Five criteria were used as a basis forselection as an “important” wetland: 1. typical or large
example of mire, saltmarsh, river, lake, tidal flat,mangrove, macroalgae stand, coral reef; 2. occurrenceof rare or endemic species; 3. occurrence of diverse animal or plant communities; 4. occurrence of a large
proportion of the total population of selected species;
5. indispensable area in the life cycle of animals orplants (feeding ground, breeding ground). In an online
database (http://www.sizenken.biodic.go.jp/wetland/index.
html, in Japanese), photographs of each site as well as
brief information on the name of the local administrative
unit in which it is located, wetland type, “coenosis” (e.g.
“mire vegetation,” “freshwater mollusc community”etc.), name of the region (other related wetland areas,
river catchment etc.) and the reason for inclusion in thelist are given. Japan was subdivided into ten regions forthe survey, separating Hokkaido, six regions in Honshu,
Shikoku, Kyushu and Okinawa (Table 2). The numberof sites in the list is highest for Kyushu (88), thesouthernmost of the main islands in Japan, and lowest
for the Tokai and Chubu region in Honshu (29). Wetlandarea is not indicated. Forty-nine different terms are used
to describe the wetland types in the list, but the distinction between some of them is unclear, and they may be
redundant. No special types the distribution of which is
restricted to Japan have been defined. Within Japan,
some types have clear regional affinities, e.g. mangrovesthat occur only on the Ryukyu island chain. Some othertypes have been recorded only in certain regions within
Japan, but the terms used to describe them are notwell-defined (e.g. “hanrangen” (“floodplain”), “irie”(“inlet”) etc.), and it seems possible that either there
might be more areas of the same type elsewhere, or the
category might have to be merged with another in orderConservation of Wetland Ecosystem Diversity

to achieve an unambiguous classification.
Wetland plant communities have been described aspart of the phytosociological inventories of Japan thatstarted in the first half of the 20th century (Miyoshi,1938). The classification system followed largely theapproach of the Zurich-Montpellier school based on the131

presence of characteristic and differential plant species,
although some authors put emphasis also on the abundance of dominant species, following the approach of
the Scandinavian school of phytosociology (Tachibana,2002). In the phytosociological classification used in the“Vegetation if Japan” (Miyawaki, 1980-1990), 18 of theTable 2 Wetland types used for the classification of wetlands in the list of “500 important wetlands of Japan” (Ministry of theEnvironment, 2001) and their occurrence in different regions in Japan. Types that belong to the same broader category ofwetland are grouped and have the same shading.

KyushuOkinawa

Shikoku

Sanin & Sanyo

43

33

30

88

55

●

●

●

●

Kinki

Tokai & Chubu

Koshinetsu & Hokuriku

Kanto

TohokuHokkaido

RegionNumber of wetlands in each region
Wetlandtype
Japanese wetland type namenumber1 Chika suikei

Tentative English translation of the wetland type

61

67

49

45

29

●

●

●

●

●

●

●

●

●

●

●

●

●

●

●

●

●

●

●

Subterranean hydrological system

2 Yusui

Spring3 Yusui chi

Spring/spring fen

4 Yusui shitchi

Spring fen/seepage area

5 KasenRiver/stream

6 Kasen jiki

River channel/floodplain

7 Hanran gen

Floodplain

8 Keiryu

Gorge

9 Kako iki

Estuary

10 Kosho(Large) lake

11 Kisui kosho

Brackish lake

12 Kaiseki ko

Lake formed by coastal regression

13 Seki ko

Lagoon lake

14 Chisho
15 Kozan kosho
16 Setsuden sogen

Snow patch vegetation

17 Shotaku chi

Paludified area

18 Shitchi rin

Swamp forest

19 Hannoki rin shitchi

Alder swamp

20 Teiso shitsugen

Fen

●

●

●

●

●

●

●

●

●

21 Chukan shitsugen

Transitional mire

●

●

●

●

●

●

●

●

●

22 Koso sitsugen(Raised) bog

●

●

●

●

●

●

23 Ensei shitchi

Saltmarsh

●

●

●

●

●

24 Kaigan shitchi

Coastal wetland

●

●
●

●

●

●

●

●

●
●
●

●

●

●

●

●

●

●

●

●

Pond/small lake●●

Alpine lake

●

●

●

●

●

●

●

●

●

●

●

●

●

●

●

●
●
●

●

Mangrove swamp
Sandy beach

27 Higata

Tidal flat

28 Kata ko higata

Tidal flat in a lagoon●

29 Kako higata

Tidal flat in an estuary●

30 Irie higata

Tidal flat in an inlet●

31 Mae hama higata

Exposed tidal flat●

32 Jinko no higata

Man-made tidal flat

33 Irie

Inlet

34 Senkai iki

Shallow marine area

●

●

●

35 Moba

Macroalgae vegetation/kelp

●

●

●

36 Toasa no kaigan

Submerged marine terrace

37 Sango sho

Coral reef

●

●

●

38 Suiro

Artificial channel, canal

●

●

●

●
●

●

●

●

●

●
●

●

●

●

●

●

●

●

●

●

●

●

●

●

●

●

●
●
●

●

●

●

●

●

●

●

●

●

●

●

●

●

Rice paddy
Fallow rice paddy●

41 Hoki suiden

Abandoned rice paddy●

42 Hasu ta

Lotus paddy●

Reclaimed wetland●●

40 Kyuko den

45 Kantaku chi●●●

39 Suiden

Irrigation pond●●●

26 Suna hama

Water retention area●●●

25 Mangurobu rin

44 Yusui chi

●

●

●

●

43 Tame ike

●
●

●

●

●

●

●

●

●

●

●

●

●

●

●

●
●

●
●
●

●

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●

●

●

●

●

46 Jari saishu ato no jinkoteki shitchi Artificial wetland in a former gravel extraction site●

47 Shitchi o fukumu han shizen sogen

Semi-natural grassland including wetlands●

48 Fukugo gata no shitchi

Wetland complex

49 Sonota no shitchi

Other wetland type

●

●

●
●

●

●

●

●

●

132

S. HOTES

49 highest-level groups contain wetland vegetation(Fujiwara, 1996). A rough indication of the spatial
distribution of vegetation classes, orders, alliances andassociations can also be drawn from the list.
Changes in wetland areas have been compiled by the
Geographical Survey Institute using topographical maps
from the Meiji and Taisho eras and comparing these tocurrent maps (Geographical Survey Institute, 2000).
According to this study, 2,111 km2 of wetlands existed in
the late 19th / early 20th century, whereas on “current”
maps (dating from 1975 to 1997) 821 km2 are indicated.
This equals a loss of about 61% of wetland area. The
figures show that wetland area is unevenly distributedwith the majority being located in Hokkaido, a muchsmaller proportion in eastern Japan and only very small
areas in western Japan. Hokkaido accounts for the largest proportion of change, but as the original area wasmuch larger than in southern Japan, it still holds thelargest wetland area. Interestingly, increases in wetlandarea are also noted in this study. In Wakayama prefecture, which has only a small absolute wetland area, atenfold rise in wetland area was reported. The largest
absolute increase of about 9 km2 is listed for Tochigi
prefecture. The causes of change were classified as
1. decrease due to reclamation; 2. decrease due tonatural causes; 3. increase due to discovery of formerly
unknown wetlands; 4. increase due to lowering of thewater table; 5. increase due to a rise in water level;
6. increase due to abandonment of rice paddies. The listof causes shows the inherent problems of monitoring
wetland area changes: the sources are not exact concerning ecosystem boundaries, and estimates of the former
extent of wetlands contain a considerable amount of
uncertainty. It is doubtful whether the “natural” causes
for wetland area decreases are indeed not influenced byhuman activity, and it is unclear whether the wetland
areas that were newly recorded because of changes inwater levels or abandonment of rice paddies are of asimilar quality to those that were lost, i.e. whether they
can indeed be counted as “new wetlands” and thus mitigate some of the overall negative trend. This cautious
view is supported by studies showing that altered waterlevel regimes can disrupt life cycles of wetland plants
and lead to biodiversity loss, although the wetland is not
physically destroyed (Nishihiro et al., 2004), and thatrice paddies if they are managed according to traditional
methods can have higher biodiversity than if management ceases (Takeuchi et al., 2003).
A different approach to estimating changes in ecosystems was taken by the Nature Conservation Societyof Japan in cooperation with WWF Japan (Plant
Community Committee, 1996). They organized a surveyof natural vegetation types considered “important for
nature conservation” and had experts evaluate the statein which they were. The vegetation classification system
was based on dominant plant species rather than floristic
criteria. The system includes 27 community groups
comprising 398 communities that are in some way
associated with wetlands in the sense of the Ramsar

Convention. Of the 7,492 “plant communities stands”
evaluated in the survey by the NGOs, about a third
stands were considered to be threatened by destruction,
declining in quality or in an unfavourable state. On asite basis, about 20% of the 3,989 locations where theplant communities were found were considered to be inneed of protective measures. The complete databaseapparently has not been updated since, but a collectionof articles on the development of certain vegetation
types and regions was published (Nature Conservation
Society of Japan & Ohsawa, 2005). Examples of successful conservation programmes as well as of destructionof sites were given, but no coherent set of quantitative
data on wetland plant community dynamics at thenational scale is available.

3. Temporal Aspects of Wetland Biodiversity
Ecosystems change constantly. Their biotic component, i.e. microbial, plant and animal communities,changes through processes like birth, growth, dispersal,
migration, death and decomposition. The abiotic component, i.e. physical and chemical properties (geology,
geomorphology, climate), is altered by physical processes and chemical reactions. Both components areinterdependent through a network of direct and indirect
effects that create positive and negative feedback cycles.
The resulting changes can be cyclic or directional, andthey can be reversible or irreversible, although the decision to which type a certain process belongs depends on
the scale of observation. These simple facts have important implications for nature conservation and restoration.
One consequence is that maintaining a certain state ofan ecosystem is possible only for a limited amount oftime, and “conserving” or “restoring” it requires someconsideration of inevitable change. It has to be statedwhether the system undergoes cyclic changes (e.g. tidal
influence, seasonal change), whether there are directional changes and how fast they are, and it is important
to know how disturbance events may counterbalance orenforce trends in ecosystem development. Information
on some of the short-term dynamics of abiotic factors is
usually available because they are collected throughroutine meteorological or hydrological measurement
schemes, but monitoring of the biotic components israrely done continuously with standardized methods.
Therefore, the information is usually snapshot-like, andlong-term information is available only for a few sites.
Because a comprehensive documentation system forecosystem change has not been established yet and because results of pilot studies are often published inscientific journals that are not easily accessible to planners and land managers, conservation and restoration
measures are taken without optimum knowledge of ecosystem dynamics. In order to overcome these problems,
results of palaeoecological investigations and long-term
ecological studies should be made available to land
managers more widely (Anderson et al., 2006).

Conservation of Wetland Ecosystem Diversity

4. Conclusions Concerning Wetland Conservation Strategies
Based on the brief review of wetland classification
on different spatial scales and the implications ofdynamic changes on different temporal scales, a numberof conclusions concerning wetland conservation andrestoration can be drawn:
1. In spite of attempts to create a unified system for thedescription of wetland ecosystem diversity, no generally accepted scheme that is suitable for all purposesand scales has been achieved. It appears that following (Sjörs, 1985) we have to accept that there is no
single most suitable system that serves all needs.
2. The Ramsar Convention’s definition of “wetland”
and the subdivision into types is general enough toaccommodate all areas and sites that may be of interest in the context of conservation, although it does
need regional specifications.
3. As long as no comprehensive database on wetland
distribution, wetland characteristics and wetland
functions across spatio-temporal scales is available,
defining regions with homogenous climatic, geological and geomorphological features (biogeographicalregions, ecoregions) can provide a guideline for arough estimate of wetland biodiversity at medium
spatial scales.
4. Within the regions thus defined, combining cartographic sources related to soils and hydrologicalunits with vegetation data yields an overview of pastand present wetland distribution. Based on these,
conservation areas and priority sites for restoration
can be selected.
5. In order to continuously improve knowledge of wetland ecosystems and to make data more accessible,
existing databases should be linked and be madeavailable through the Internet. Efforts towards quantitative criteria for classification and a clearer terminology should be continued.
6. Although it is self-evident that whole hydrologicalunits need to be considered if the integrity of wetland
ecosystems is to be preserved, land use conflicts
commonly prevent putting this into practice. Support
systems that help to solve such conflicts need to beestablished and/or strengthened.
7. In order to accommodate faster environmental
change due to anthropogenic alterations of climate,protected areas have to be enlarged where this is
physically possible, and they have to be spatially arranged so that biota can reach new habitat if current
distribution areas become unsuitable.
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(Received 13 December 2007, Accepted 11 March 2008)