To main content


MadMacs (mass development of aquatic macrophytes; causes and consequences of macrophyte removal for ecosystem structure, function, and services) aims to determine the causes of mass development of water plants, and to study the direct and indirect consequences of their removal on ecosystem functions and services.

Vann med vannplanter
Project period
Water JPI
External webpages
Research section
Freshwater Ecology

About the project

MadMacs is a Water JPI project led by NIVA.


  • Mass development of aquatic macrophytes (= water plants) in rivers and lakes is a worldwide problem, and substantial resources are spent on macrophyte removal. However, measures are usually inefficient and macrophyte stands either quickly grow back or their removal causes other problems.
  • The specific regional causes of macrophyte mass development are still poorly understood, most likely because there is typically a combination of factors which together cause nuisance growth (multiple pressures).
  • Macrophyte mass developments have known negative effects (e.g. causing fish kills and impairing the use of the water body for swimming or boating), but well-developed macrophyte stands also have many benefits (ecosystem services). These are often poorly known to the public or to water managers.


  • Analyze which combination of natural conditions and stressors can cause mass development of macrophytes
  • Quantify the effect of macrophyte presence/removal on structural and functional diversity of aquatic organisms (biodiversity)
  • Quantify the effect of macrophyte presence/removal on nutrient and carbon retention and greenhouse gas emission (water quality)
  • Quantify the effect of macrophyte presence/removal on the full range of ecosystem services
  • Develop a tool to assess and balance benefits and costs of macrophyte removal

Case studies

We will execute a set of “real-world experiments” in a harmonized design at six sites across five countries (Norway, Germany, France, South Africa and Brazil).

The MadMacs project is funded through the 2017 call of the Water Challenges for a Changing World Joint Programme Initiative (Water JPI), with the national funders Research Council of Norway (297202/E10), German Federal Ministry of Education and Research (033WU005), the French National Research Agency (N° ANR-18-IC4W-0004-06), the South African Water Research Commision (K5/2951), and Fundação Araucária in Brazil (N° 186/2019).

Additional funding is provided by Krypsiv på Sørlandet, NIVA and NMBU to support a PhD-student in Norway.