Managing conflicting conservation goals: the case of the Grecian Juniper endemic woods and the Great Cormorant

In 2006, the Public Institution Galicica National Park, in cooperation with the Macedonian Ecological Society, organized a workshop to address a pressing management problem – the impacts of the largest nesting colony of the great cormorant (Phalacrocorax carbo) in the country, on the old stand of the Grecian juniper woods on the Golem Grad Island in the Greater Prespa Lake, North Macedonia – a priority habitat type in the European Union (code *9560). A few decades ago, the growing nesting colony on the Island of Vidrineci, in the Lesser Prespa Lake, Greece, has gradually caused a complete die-off of all Greek Juniper trees (Juniperus excelsa) on that small island. While controlling the growth of the nesting colony of the great cormorant was considered, among other options, the workshop participants, including park staff, scientists and local communities, eventually agreed that more information was needed before taking any direct action.

The first Standard Operating Procedure (SOP) or protocol for monitoring the impacts of the great cormorant colony on the Grecian juniper woods on the Golem Grad Island was developed in 2010, as one of the 22 monitoring protocols constituting the first long-term monitoring programme of Galicica National Park.

The implementation of the SOP for the great cormorant requires significant logistical support (off road vehicles, a boat) and sustained human effort over several days in challenging environmental conditions.

The first incomplete measurements were made during the testing period of the monitoring programme in 2010, but it was only in 2013 that the protocol was fully implemented. By 2013, each tree bearing a cormorant nest on it since 2010 was marked with a numbered plastic tag, in addition to recording its GPS coordinates (492 trees in total; see the picture on the left). The field measurements include the number/location of the trees bearing at least one nest, tree species, general condition of the tree (dead or vital), and number of active and/or inactive nests.

The measurements were repeated in 2016, in cooperation with the Society for the Protection of Prespa from Greece and the Macedonian Ecological Society (MES) and then in 2019 and 2020 in cooperation with the MES and including two new park staff.

While the changes in the teams implementing the SOP may be responsible for some inconsistencies in the implementation of the SOP, the results from the four measurements clearly show an upward trend in the number of active nests, as can be seen in the graph. The data also show that the number of occupied trees has an increasing trend as well.

The information about the nesting colony of the great cormorant is currently being complemented by surveys on the nests of the grey heron that are embedded within it, while a master degree research is underway to determine the impact of the abiotic factors and pathogens, on the annual growth of the old Greek Juniper trees using a dendrochronological analysis.

*  The article was written in cooperation with the staff of the Public Institution Galicica National Park and is the first in a series of several articles sharing the experience of PONT grantees in monitoring biodiversity in the Wider Prespa Area.