Wetlands perform many essential ecosystem services-carbon storage, flood control, maintenance of biodiversity, fish production, and aquifer recharge, among others-services that have increasingly important global consequences. Like biodiversity hotspots and frontier forests, the world's largest wetlands are now mapped and described by an international team of scientists, highlighting their conservation importance at the global scale. We explore current understanding of some ecosystem services wetlands provide. We selected four of these wetlands (the largest peatland, West Siberian Lowland; the largest floodplain, Amazon River Basin; the least-known wetland, Congo River Basin; and the most heavily developed wetland, Mississippi River Basin), and we illustrate their diversity, emphasizing values and lessons for thinking big in terms of conservation goals. Recognizing the global significance of these wetlands is an important first step toward forging global conservation solutions. Each of the world's largest wetlands requires a basinwide sustainable management strategy built on new institutional frameworks-at international, national, and regional levels-to ensure provision of their vital services.

Summary 1.As an aid for restoration projects, the relative potential for plants to immigrate to sites after severe disturbance was investigated and an index developed to determine their relative immigration potential. The goal was to establish baseline knowledge for the species pool in severely disturbed sites prior to restoration. The method was based on the identification of potential colonists, inventories of populations in surrounding vegetation and autecological information on their maximum fecundity and dispersal by wind, water or animals. 2.The method was applied to milled peatlands in south-eastern Quebec, Canada, after the cessation of peat extraction activities. Thirty-two species, ranging from mosses to trees, which are common in natural or abandoned milled peatlands in southern Quebec, were selected as potential colonists. 3. Populations of study species differed markedly in edges of milled peatlands in terms of their abundance, presence and presence of fertile plants. An edge effect was apparent where the populations of many species varied as a function of distance from milled surfaces, caused, in part, by drainage. 4. Mosses had relatively high potential to immigrate to milled bogs because of their high fecundity and the wind-dispersal ability of their spores. The scarcity of mosses in abandoned milled bogs did not appear to be a result of the lack of immigrant propagules. Herbs had relatively low immigration potential, due to their rarity in edges, but herbs such as Eriophorum vaginatum were able to recolonize milled bogs in spite of this low potential. Shrub species generally had high immigration potential because of their abundance at edges and the high dispersal ability of propagules by wind, water and animals. Trees had high immigration potential due to their abundance at edges and their wind-dispersal abilities. 5. Synthesis and applications. An index of immigration potential provides information on the probable initial species pool after severe disturbance, against which the effects of local habitat suitability and establishment factors can be added to assess probable successional patterns. Its flexibility and applicability to varied life forms should make it useful for diagnosing recolonization bottlenecks in a wide variety of disturbance and restoration situations. It also allows for an assessment of the relative need for introducing species during the restoration of severely disturbed environments.

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L. 2002. Wind erosion and surface stability in abandoned milled peatlands. Can. J. Soil Sci. 82: 85-95. Peatlands exploited for their peat by the method of milling are poorly recolonized by plants after the cessation of extraction activities, in part due to unstable peat substrates. Wind erosion has been suspected to play a role in this instability. Four studies were conducted to investigate the role of wind erosion on abandoned milled peatlands. A wind tunnel experiment was performed to evaluate the erodibility of dry, loose peat as a function of its degree of decomposition. A second wind tunnel experiment was conducted to determine how crusted peats differ in their resistance to erosion as a function of their degree of decomposition, without the input of abraders. Third, wind profiles were measured in milled, revegetated and natural peatlands in southeastern Québec to determine their aerodynamic roughness length. Finally, field measurements were made at three abandoned milled peatlands through two field seasons to characterize substrate stability and particle movement. In the wind tunnel, the erodibility of loose surface peat decreased with increasing decomposition and was predicted by their equivalent diameter to mineral particles 0.84 mm in diameter. However, once surface crusts formed, peats were all resistant to erosion. Surfaces of abandoned milled peatlands were aerodynamically smooth; therefore, exposed surface elements are subject to strong erosive forces during wind events. The greatest subsidence on abandoned milled peatlands occurred in the spring, prior to the surface movement of particles. Erosion during the summer could not be clearly detected. The instability of the peat surface remains a constraint for the restoration of abandoned milled surfaces.Key words: Peat, cutover peatland, wind erosion, soil crusts, roughness length, soil stability Campbell, D. R., Lavoie, C. et Rochefort, L. 2002. Érosion éolienne et stabilité de la surface dans les anciennes tourbières commerciales. Can. J. Soil Sci. 82: 85-95. Les plantes recolonisent mal les tourbières dont on a récolté la tourbe une fois que les activités commerciales ont cessé, en partie à cause de l'instabilité du substrat. On soupçonne que l'érosion éolienne joue un rôle dans cette instabilité. Les auteurs ont entrepris quatre études dans l'espoir d'élucider le rôle de l'érosion éolienne dans les tourbières commerciales laissées à l'abandon. Une expérience en soufflerie a permis d'évaluer l'érodabilité de la tourbe sèche et lâche d'après son degré de décomposition. Un deuxième essai en soufflerie a contribué à déterminer de quelle façon la résistance des tourbes encroûtées à l'érosion varie avec le degré de décomposition, en l'absence d'abrasifs. Dans le cadre de la troisième étude, on a établi le profil des vents dans les tourbières exploitées, remises en végétation et naturelles du sud-est du Québec afin de préciser le paramètre de rugosité aérodynamique. Enfin, les auteurs ont pris des relevés sur le terrain dans trois tourbières commerciale...