Abstract
Possible consequences of climate change in one of the world’s largest wetlands (Ibera, Argentina) were analysed using a multi-scale approach. Climate projections coupled to hydrological models were used to analyse variability in wetland water level throughout the current century. Two potential scenarios of greenhouse gas emissions were explored, both resulting in an increase in the inter-annual fluctuations of the water level. In the scenario with higher emissions, projections also showed a long-term negative trend in water-level. To explore the possible response of biota to such water-level changes, species-area relationships of flora and aerial censuses of macro-fauna were analysed during an extraordinary dry period. Plant species richness at the basin scale was found to be highly resistant to hydrological changes, as the large dimension of the wetland acts to buffer against the water-level variations. However, local diversity decreased significantly with low water levels, leading to the loss of ecosystem resilience to additional stressors. The analysis of macro-fauna populations suggested that wetland provides refuge, in low water periods, for the animals with high dispersal ability (aquatic and migratory birds). On the contrary, the abundance of animals with low dispersal ability (mainly herbivorous species) was negatively impacted in low water periods, probably because they are required to search for alternative resources beyond the wetland borders. This period of resource scarcity was also related to increased mortality of large mammals (e.g. marsh deer) around water bodies with high anthropogenic enrichment and cyanobacteria dominance. The synergy between recurrent climatic fluctuations and additional stressors (i.e. biological invasions, eutrophication) presents an important challenge to the conservation of neotropical wetlands in the coming decades.
Highlights
Freshwater wetlands can be strongly affected by climate change as their spatial and environmental characteristics are closely dependent on the water balance of the basin [1,2]-[3]
In the A2 scenario, a moderate decline in the mean water level was found in the second half of the century (20.32 m in relation to the mean historic level)
A more consistent fall of the water level was predicted for Laguna Galarza where both scenarios led to a decline, 20.13 m and 20.47 m in the first and second half of century for the B2 scenario, and 20.41 m and 20.77 m in the first and second half of century for the A2 scenario (Table 2, Fig. 2)
Summary
Freshwater wetlands can be strongly affected by climate change as their spatial and environmental characteristics are closely dependent on the water balance of the basin [1,2]-[3]. The Neotropics include several of the world’s largest freshwater wetlands, associated with the vast floodplains of large South American rivers (e.g. Amazon, Orinoco, Parana, Paraguay). Their flora and fauna show outstanding species richness with an important fraction of endemic species [4,5]-[6]. Long-term trends of water level in wetlands may have special relevance for species richness due to their impact on ecosystem size and habitat diversity [7]. Short-term fluctuations of the water level determine the ecosystem stability, which influences the species diversity and composition [8,9]
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