Tuesday, August 7, 2007 - 4:20 PMOOS 20-9: River floodplain polyculture: Exploiting flooding as an engine of biodiversity in the Tisza River Basin
Jan Sendzimir, International Institute for Applied Systems Analysis and Zsuzsana Flachner, Hungarian Academy of Sciences.
Diversity is commonly regarded as fundamental strategic hedge in ecological agriculture against all sources of environmental variability, especially extreme events and trends in weather and pest outbreaks. While it may be counter-intuitive to any society that has used technology to minimize disturbance, some socio-ecosystems did exist where appreciable biodiversity levels were maintained by disturbance. Flooding is examined here in the Hungarian reach of the Tisza River Basin (TRB) as an example of an intermediate level of disturbance that, when unconstrained by hydro-engineering, sustained landscape complexity (diversity of floodplain habitats and topographical structure), maintained hydraulic connections that sustain nursery and migratory functions and stored water during times of drought, and distributed and mixed fallen fruit in novel combinations that stimulated agro-biodiverstiy. Before the implementation of the original Vásárhelyi river engineering plan in the 1870s, these structuring and distributional functions maintained a spatial heterogeneity of structure and biodiversity, a dynamic landscape mosaic where humans cultivated hundreds of varieties of fruit and nuts in the Tisza river floodplain. As regional decline appears driven by recurrent and inter-related crises of ecology, economy and society, the conversion of the TRB from a fruit/nut/ fishery polyculture to a wheat or corn monoculture is increasingly questioned, and pre-industrial production patterns are studied as models for future eco-agriculture. Mechanisms developed by pre-industrial societies to use flooding to sustain both agro- and eco-biodiversity are proposed here as processes to test in current pilot projects that remove hydro-engineering structures (dikes, drainage channels) in the experimental “renaturalization” of the TRB floodplain.