D2.2.2 – Report on change in reed extent by changing numbers of muskrat and Coypu

Date: 30/10/2023
Author: E.E. van Loon, C. Black

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This report gives the change in reed extent for the project areas over the period 2019 to 2023 and compares it to changes in Muskrat and Coypu population sizes over the same period.

At this level of aggregation (the level of project areas) the reed vegetation extent was relatively stable over the duration of the LIFE MICA project. Still some trends are still visible: in three areas an increase was seen and in two areas a slight decrease. However, it turns out that these changes are not significantly related to changes in the muskrat and/or coypu population sizes (at the scale of project areas).
A more fine-grained analysis (a grid with a 5×5 km resolution) could only be done for two of the project areas (areas 8 and 9) because only in these there were sufficient sub-areas with both increases and decreases in muskrat abundancies. At this scale, a pattern did appear. The areas with an increase in reed area have no muskrats present (Area 8) or very small (Area 9) muskrat abundances. While in the areas with large decreases, larger muskrat populations are present.

These results indicate that to establish meaningful increases in reed vegetation extent, muskrat densities should be very low. However, the results should also be interpreted with care (and should be confirmed in other locations ), because there may be co-varying factors at play in these areas that could also influence reed vegetation dynamics.