Background The Paul de Arzila (Arzila marsh) is a wetland in the valley of the river Mondego in the Coimbra municipality and surrounding areas. It is a biogenetical reserve with an area of 150 ha framed in a protected area of 535 ha, where 119 species of birds, 12 of mammals, 10 of reptiles and 13 of fish have been inventoried. In hosts key habitats covered by the Habitats Directive, including the project’s target habitats: natural eutrophic lakes (3150), streams with muddy banks with Chenopodion rubri and Bidention vegetation (3270) and Salix alba galleries (92AO). Key species include the Western marsh harrier (Circus aeruginosus), the purple heron (Ardea purpurea), the Spanish pond turtle (Mauremys leprosa), the Iberian emerald lizard (Lacerta schreiberi), the European otter (Lutra lutra) and various species of ray-finned fish including the ruivaco (Rutilus macrolepidotus) and Iberian nase (Chondrostoma polylepis). The area has been classified as a Special Protection Area (SPA) and proposed as a Site of Community Interest (SCI), but despite this it is threatened with habitat loss owing to expansion and ageing of the reedbeds (Phragmites australis), organic pollution and excessive sedimentation and eutrophication. These factors have reduced the water column, leading to colonisation by species characteristic of less humid habitat types and subsequent reduction of the reproduction areas for target species. Objectives The project aimed to draw up and partially implement a Paul de Arzila management plan to increase habitat diversity and the breeding population of target species. It aimed to increase all three target habitats by at least 30% each and see greater numbers of key species. Particular targets included seeing a 20% increase in the population of ruivaco and around 3 more nesting couples of each of the Western marsh harrier and the purple heron. It also hoped to achieve a 60% decrease in organic pollution and a 40% decrease in chemical pollution. Planned measures included the purchase of 68 ha of marsh ecosystem, reduction of the reedbank, creation of open water areas and removal of excessive sediments from the marshes. The project intended to set up facilities to treat wastewater by plants, monitor water quality and hydrology, and carry out surveillance of target species populations. The project was also to include measures to increase local awareness of the importance of this wetland and build an observation tower. Results Despite severe delays caused by financial restrictions imposed by the Portuguese Ministry of Finance - which prevented the drafting of a full management plan for the target area - the project was still able to increase the habitat diversity of the marsh ecosystem in the targeted area with consequent benefits to vulnerable species. The beneficiary purchased 33.3 ha of targeted marshland from 175 land owners to be managed exclusively for conservation purposes. This extended the total area of protected marshland in Arzila to 65 ha. The project intervened across a total of 20 ha of the acquired marshland to tackle the decline of natural habitats. It removed 12 ha of common reed (Phragmites australis), and created 2 ha of open water areas. It also spread key vegetation types including Myriophyllo-Nupharetum over 1 ha, duckweed (Lemnetum minoris) over 0,5 ha, cattails (Typho-Scirpetum) over 2 ha and Scirpo-Phragmitetum over 5 ha. Sediment was removed from 22 ha of marshland. This will counter the progressive eutrophication of water channels and return acceptable conditions for egg deposition and fish and amphibians larvae development and increase water depth to the benefit of numerous aquatic species. Moreover a total of 15 km of ditches were restored in four different areas of the SPA - Vala do Meio, Vala da Costa, Ponte do Passo and Vala dos Moinhos - allowing a better control of the water levels inside the project implementation areas. The beneficiary introduced a tertiary treatment process into a facility for treatment of wastewater by plants. This avoided the need to construct a totally new facility, whilst still reducing the contamination of the water in the marshlands, which was monitored. Further monitoring work was carried out on key species of both fauna and flora. The project saw the reproductive population of the purple heron (Ardea purpurea) double as well as increases in other bird species. However, the number of reproducing pairs of the Western marsh harrier (Circus aeruginosus) remained the same during the project. There was even a slight reduction in the population of the ruivaco (Rutilus macrolepidotus), although this is likely to be a continuation of the previously existing problems and the project’s actions should see this trend change in the coming years. Additional infrastructure development improved safe visitor access to the marshes, including a 7m-high observation tower - particularly for viewing bird species on the marsh - and an elevated 60m pathway through the reedbed. Further information on the project can be found in the project's layman report (see "Read more" section)