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Mass development of aquatic macrophytes (water plants) in rivers and lakes is a worldwide problem. Across the globe, both native and invasive species of macrophytes may exhibit nuisance growth. Mass development of macrophytes generally is perceived as a problem, and considerable resources are spent on macrophyte removal. However, macrophytes, including very dense stands, also have positive effects on aquatic ecosystems.

Among the ecosystem services provided by macrophytes are e.g. nutrient removal and retention (i.e. they contribute to the provision of clean water), as well as the provision of habitats for a diverse flora and fauna (i.e. they support life below water). Since macrophytes are food and habitat for waterfowl and fish, they contribute to providing a source of protein for low-income riparian subsistence (human) communities. Macrophytes also may prevent blooms of harmful cyanobacteria and reduce the emissions of greenhouse gases such as methane. Unfortunately, most ecosystem services provided by macrophytes are largely unknown to the public and water managers. Consequently, management decisions are based on a prevailing negative perception of macrophytes rather than a rational knowledge-based decision.

Potential negative consequences of macrophyte removal are generally not considered in management decisions, and follow-up problems often come as a surprise. MadMacs will address the multiple and interacting causes leading to macrophyte mass development and will provide information on both the benefits and dis-benefits of macrophyte removal across a wide geographic area.