Biodiversity net gain
Further details on the systemic and synthesis for this European Green Deal Criterion are available in the MERLIN Deliverable Report page 35.
Quantity of habitat restored
In total, 287 km of free-flowing river were restored at nine case-studies, including reconnecting rivers with their floodplains (Danube, Emscher, Ervidel, Kvorning, Rhine and Scheldt) and removal of barriers to restore flow continuity (Deba, ES) (Table 1).
In total, 1528 ha of floodplains were restored (Table 1). This is the area of over 12,000 Olympic-size swimming pools, which Illustrates the potential this provides for flood storage capacity, increasing the climate resilience of these regions.
| CS name | Free-flowing river reconnected (km) | Area of floodplain re-connected (ha) | Area of peatland or wetland restored (ha) | Change |
|---|---|---|---|---|
| CS01 — Kvorning wetland rewetting DK | 9.5 | 230 | 500 |  |
| CS02 — Deba barrier removal ES | 18.5 | |
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| CS03 — Beaver river engineering SE | 10,000–1,000,000 | |
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| CS04 — Room for the Rhine NL | 4.4 | |
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| CS05 — Kampinos wetland rewetting PL | 362 | |
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| CS06 — Hutovo Blato peatland rewetting BiH | 1,490 | |
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| CS07a — Danube floodplain restoration AT (Demo site) | 4.3 | |
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| CS07b — Danube sidearm reconnect HU (Demo site) | 1.8 | 66 | |
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| CS08 — Danube floodplain reconnect RO | 400 | |
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| CS09 — Tisza floodplain rewetting HU | 263 | |
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| CS10 — Blue Belt Germany DE | 1.5 | |
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| CS11 — Emscher basin restoration DE | 241 | 155 | |
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| CS12 — Lima river floodplain forest restoration PT | 32 | |
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| CS13 — Sorraia river restoration PT | 49 | |
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| CS14 — Komppasuo peatland rewetting FI | 120 | |
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| CS15 — Tzipori basin restoration IL (Implementation site) | 1.5 | |
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| CS16 — Upper Scheldt restoration BE (Implementation site) | 2.4 | |
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| CS17 — Forth basin restoration UK | 3 | |
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| CS18 — Ervidel river restoration PT | 2.0 | |
| CS count | 10 | 8 | ||
| CS% | 53% | 42% | ||
| Sum | 287 | 1,528 | ||
Quality of habitat restored
Increases In habitat quantity do not mean that quality is improved, this may depend on further management measures, such as pollution reduction. Data on habitat quality were often unavailable or consisted of only 1 year before or after restoration, making a robust assessment of change unreliable.
The Lima case-study in Portugal, Illustrates the use of the indicator "% of habitat area in favourable condition". Their assessment showed a consistent increase in % area in favourable condition in 3 of 4 habitats only one year after restoration (Figure 1). The fourth habitat, water crowfoot rivers, was already 100% in favourable condition pre-restoration and remained so one year post-restoration, indicating that the floodplain restoration had no negative impact on the river vegetation.
WFD ecological quality ratios of biological quality elements
WFD ecological quality ratios (EQRs) are widely available across Europe and are also recommended as an Indicator of freshwater biodiversity quality — representing change In community composition. Normalised EQR (nEQR) values, where the EQR scale Is standardised for class widths of 0.2, can be used to compare biodiversity quality change across freshwater types and countries.
The value of using nEQR is Illustrated for benthic invertebrates in three stretches of the Deba River (Figure 2). These show a positive improvement, moving from moderate status to good status, although the main improvement occurred 1 year pre-restoration and a return to moderate conditions in the Middle Deba occurred in the 2nd year post-restoration.