Srebarna Nature Reserve

An increase in the visitor levels in the buffer zone of the Property with peaks at certain periods, i.e. weekends in spring and autumn season with recreational purposes, has been observed (State Party of Bulgaria, 2024). Recreation and tourism activities may disturb the nesting population of the Spoonbill (Triplet et al. 2008). According to EEA (2013) walking and cycling have low and negative influence in small parts of the property and its buffer zone.

The area around the property covered by human settlements with houses and yards has increased by 156% since 1948; the trend continues (Biserkov and Naumov 2012). These changes have had significant impact on habitats size and quality in the area around the property and its buffer zone (Biserkov and Naumov 2012). The current urbanized area is not habitable by many mammals, reptiles and amphibians (Biserkov 2012, Biserkov and Naumov 2012). These developments also affect the ecological connectivity of ecosystems in the property with those in the surrounding area. According to EEA (2013) urbanised areas and human habitation (including such effects as disturbance, resource use, noise and pollution which are threated here in other threat categories) have high, but neutral influence on the area around the property and its buffer zone.

Since 1948, the area covered by the road and highway network (1st to 4th grade) in the area around the property has increased by 240%; the trend continues (Biserkov and Naumov 2012). This area is certainly no suitable as a habitat for all mammal, reptile and amphibian species present in the property and its surrounding area (Biserkov 2012, Biserkov and Naumov 2012). The gravel road around the property contributes to wildlife disturbance by noise, cars, recreationists and poachers (IUCN Consultation 2013) and has an overall negative impact on the property (State Party of Bulgaria, 2024). Concerning the measures for the protection of the Great Bittern in Bulgaria, Shurulinkov (2012) recommends speed reduction and control along the road from Silistra to Ruse, in the section close to the property. Infrastructure in general is mentioned as a threat to Eurasian Spoonbill (Triplet et al. 2008) and EEA (2013) reports high influence from transport networks in the area outside the property and its buffer zone, although this is classified as neutral.
The construction of roads and the long delay in constructing roadside ditches has led to erosion and runoff of large amounts of sediments into the lake (Management Plan, 2016).

Birds, otters and terrapins get entangled and drowned in fishnets while diving (Robinson and Hughes 2005, Cheshmedziev 2012, IUCN Consultation 2013, Birds in Bulgaria 2013). Many individuals of the Ferruginous Duck get entangled and drowned in fishnets while diving/foraging in the Danube or the neighbouring wetlands and fishponds in Romania (Cheshmedziev 2012). According to EEA (2013) commercial fishing has high negative influence in the area around the property and its buffer zone: Due to commercial fishing in the area surrounding the property and its buffer zone, the quantity of fish available to waterfowl is reduced, forcing birds to forage in other areas (e.g. in Romania) which is more energy demanding (IUCN Consultation 2013).

According to EEA (2013), trapping, poisoning, and poaching (including illegal fishing) have medium negative influence on 80% of the territory of the property and its buffer zone. Illegal fishing has been occasionally observed (State Party of Bulgaria, 2024), but is considered under control and significantly minimized (IUCN consultation, 2024). Due to the lack of direct data on the quantities of fish caught by poachers, as well as the lack of data on catches of legal sport fishing in designated areas, the extent of overfishing in the lake is difficult to estimate (Management Plan, 2016). However, it is assumed that illegal fishing in the property and its buffer zone, has contributed to a decrease in the quantity of fish available to waterfowl, forcing some birds to forage in other areas (e.g. in Romania) which is more energy demanding (IUCN Consultation 2013). Illegal fishing is a source of disturbance to the Greylag Goose (Ivanov and Dereliev 2011), Spoongbill (Triplet et al. 2008), other waterfowl (MoEW et al. 2012) and wildlife in general (IUCN Consultation 2013). The impact to waterfowl is particularly high during the nesting period (Cheshmedziev 2012).

Siltation and eutrophication resulting from increased sediment and nutrient input and retention are very serious threats, which compromises ecosystem function and accelerates the process of succession of the lake ecosystem to swamp to mire to wet meadow (LT Konsult Ltd. 2012, Kamburova 2012, EU 2015). The construction of dykes between the River Danube and Lake Srebarna has reduced the connectivity with the river and decelerated the flushing out of sediment and organic matter from the lake. Excessive development of reeds, caused by the decreased water circulation, risk to overload the ecosystem with organic matter and cause oxygen deficits when decomposing. Nutrient inputs have increased from wastewater deriving from the village of Srebarna and runoff from surrounding agriculture, leading to the siltation and fast eutrophication of the lake (Gartsiyanova and Kitev 2023). In addition, large quantities of excavated soil from road constructions are flushed into the lake with surface water runoff during flooding (Management Plan, 2016). Conflicts of management interests between farming and conservation exist (State Party of Bulgaria, 2024).
The illegal dumping of household waste form the village of Srebarna is a source of organic pollution of the property, and thus contributes to its fast eutrophication (RIS 2002, MoEW et al. 2012, IUCN Consultation 2013, Birds in Bulgaria 2013). It also introduces many alien plant species in the property and its buffer zone (Birds in Bulgaria 2013). Some household waste is also washed into the property by heavy rains from an old landfill site outside the village of Srebarna. Local population often improperly dispose plastic bags and other kinds of waste in the property, adding to the nutrient load of the lake (IUCN Consultation 2013) (reportedly decreasing trend; State Party of Bulgaria 2014, 2024). Floating waste, mainly plastics, brought in with high waters from the Danube can be limited by periodic collection and removal (Management Plan, 2016), but without the participation of the users themselves (locals, tourists, fishermen) pollution cannot be completely prevented (Management Plan, 2016).
In 2003 began the construction of a treatment plant for the wastewater from Srebarna village. However, due to the small number of households in the village the volume of wastewater was not sufficient to effectively operate the sewage system, leading to formation of compacted effluent in the sewers. Over the years, the sewage started to fill up and during heavy rains the collector shafts overflow, discharging untreated water into Lake Srebarna and thus contributing to its fast eutrophication (IUCN Consultation 2013; Management Plan, 2016). Monitoring results have shown a significant load of nitrogen and phosphorus compounds in the lake water (Gartsiyanova and Kitev 2023). There is no data on the volume of wastewater flowing into the lake, but it is urgent to put the treatment plant into full operation, to protect the collectors against overflow and stop the discharge of untreated wastewater into Srebarna (Management Plan, 2016). Nutrients from the pig farm near Kalnezha reach Lake Srebarna via the River Kalnezha and groundwater, and thus contribute to the eutrophication of the lake (RIS 2002, Kraleva et al. 2012, IUCN Consultation 2013).
According to EEA (2013) eutrophication has high negative influence on 50% of the territory of the property and its buffer zone.

Impaired water balance resulting from climate conditions and strong modifications of the natural state of the Danube River incl. construction of hydro-energetic facilities and waterway maintenance (IUCN consultation, 2024). In the past, the natural hydrology in the watershed of the property has been significantly modified through construction of nine dams in 1979 and 1994 (Nikolova et al. 2010; State Party of Bulgaria, 2024), as well as the draining of the Aydemir Lowland (EU 2015). The construction of hydro-energetic facility upstream, for example Portile de Fier/Zhelezni vrata/Djerdap hydro-energetic system of dams on the border between Romania and Serbia, led to irregular rate of the Danube River water which directly affects the site. These facilities have prevented the natural flow of sediments from upstream which has led to reduction of the altitude of the river bed. That reduces the probability for seasonal flooding of the river since much larger water quantity is required.
This seasonal flooding used to remove sediments and nutrients from the lake and maintained the riverine forests on the island (BSPB 2013). The bottom changed from hard and sandy to become muddy and unstable. As biomass builds up and water circulation decreases, many of the floating reed islands take root, making the nests of waterfowl and wading birds accessible to predators. Demolition of the dikes would be an important measure to address these threats and partly restore the natural hydrological regime. However, due to socio-economic factors it is only feasible to remove a short section of the 1979 dike (Management Plan, 2016).
A "Western Canal with a Spillway" has been built, which restores the water regime in the lake, limits the inflow of nutrients, limits succession processes and minimises silt deposition. The canal ensures the necessary water levels in the lake during the dry period and sufficient water flow in the lake to remove accumulated sediments and colloidal silt (RIEW-Ruse 2024; State Party of Bulgaria, 2024).

EEA (2013) reports high influence from electricity lines on the area outside the property and its buffer zone, although this is classified as neutral. The 2017 status report for the Dalmatin Pelican also ranks collision with power lines as a high threat to these birds in Bulgaria (Catsadorakis and Portolou, 2017). However, no specific information is available on the effects of the values of the property.

In the past, one of the reasons for the decrease of bird species composition and abundance in the property were the direct and indirect toxic effects of rodenticides applied in 1989 (Michev et al. 1998). In 2003, three Lesser White-fronted Geese were found dead at Srebarna among 123 dead Greater White-fronted Geese; it is thought the birds had been poisoned by rodenticides, either in Bulgaria or Romania (Jones et al. 2008). No updated information has been found on this topic.

Valuable habitats are lost due to the removal of riparian vegetation around the farms in the vicinity of the property and its buffer zone (MoEW et al. 2012, Biserkov 2012). According to EEA (2013) management of aquatic and bank vegetation for drainage purposes have medium negative influence in the area surrounding the property and its buffer zone.

Another significant issue is the spread of invasive alien plant species. It is a result by both the natural capabilities of the particular species to spread and the favorable conditions created by impairing of the natural state of the site over the years, including unsustainable forestry practices, multiple changes of land use and the disappearance of grazing livestock (IUCN consultation, 2024). Control of invasive species is a permanent necessity (State Party of Bulgaria, 2024). Forest formation of the Grey Willow combined with hydrophyte formations are key factor for the degradation of the lake (closing off of water body, increasing of bottom substrate etc.; Zhelezov 2010, Kamburova 2012). The fast spread of the Grey Willow is a consequence of deteriorated water circulation in the property and accumulation of sediments. Over the last 20 years, the percentage of Grey Willow has grown from 5% to more than 55%. In addition, most of the willows are over 10 years old and their biomass is significantly higher than that of the reeds they have replaced (Management Plan, 2016). The Silver berry outcompetes the local and typical species and causes fragmentation of the reed bed where Dalmatian Pelicans and other fish-feeding birds breed (MoEW et al. 2012, IUCN Consultation 2013). The ecological change in the property is also brought about by the forestation and afforestation of extensive areas in the vicinity of the property using alien tree species, such as Austrian Pine, Hybrid Poplar, Black Locust, Common Gloxinia, and Oleaster (IUCN Consultation 2013). According to EEA (2013) invasion by exotic species has medium negative influence on the property and its buffer zone.
Periodic actions aimed at control of spread and abundance of invasive and hyper-abundant species is necessary. Two large scale projects have been completed - one in 2015 and the second in 2018. Currently one project is undergoing focused at reduction of the main hyper-abundant species (State Party of Bulgaria, 2024).

Poaching and other illegal activities is related to poverty among the local residents (CLGE 2001; State Party of Bulgaria, 2024). The decline of traditional activities in recent decades and the lack of alternative employment are at the root causes of low incomes. Low incomes and lack of local capital are serious constraints to achieving both conservation goals and sustainable development (Management Plan, 2016).

Since 1948, the area around the property covered by non-irrigated farmland has increased by 919% (with positive trend) and the area covered by Vineyards has increased by 157% (unknown trend) (Biserkov and Naumov 2012). Those modifications and the consolidation of areas under cultivation have created marginally suitable or unsuitable habitats for the mammal, reptilian and amphibian populations around the property and its buffer zone (Biserkov 2012, Biserkov and Naumov 2012). Agricultural expansion affects the quality of habitat suitable for the Eurasian Spoonbill around the property and its buffer zone (Triplet et al. 2008) and in general has medium negative level of influence on some 5% of territory of the buffer zone of the property (EEA, 2013; Gartsiyanova and Kitev 2023). Agricultural runoff is considered an additional serious threat to the water quality of the site.

While hunting within the boundaries of the site is strictly forbidden, in the vicinities of the site there is no prohibition for this activity despite the important bird migratory routes passing above those areas. Isolated cases of poaching inside and outside the Property have occurred (State party of Bulgaria, 2024). Goose- and duck hunters often shoot from a pier or a boat on the Danube (CLGE 2001). The Greylag Goose and other species are disturbed by hunters (Ivanov and Dereliev 2011). In the past threats posed by hunting have increased due to lack of control, surveillance and law enforcement (IUCN Consultation, 2020; Management Plan, 2016). The principal game species around the property and its buffer zone are the Wild Boar, Hare, Ring-necked Pheasant, Greylag Goose, and Quail (CLGE 2001). According to Ivanov and Dereliev (2011) hunting disturbs the Greylag Goose wintering population; poaching (including both illegal hunting and illegal fishing) as an important source of disturbance for all wildlife (IUCN Consultation, 2013). A new scheme is needed to protect and combat poaching in the property (IUCN Consultation, 2020; Management Plan, 2016). Joint actions are taken between the Regional inspectorate of environment and water - Ruse and the Ministry of the Interior, aimed at preventing of illegal actions and catching of the offenders (State Party of Bulgaria, 2024).

The pressure from predators (racoon dogs in particular, but also wild boars, jackals, crows, foxes) account (partly) for the low success of the chicks of the Dalmatian Pelican at the property (siturbance and consuption of eggs; Crivelli 1996, Triplet et al. 2008, Michev and Kamburova 2012; State Party of Bulgaria, 2024).
If there is a long-term drought in the area and no measures are taken to improve the water balance of the lake, many of the floating reed islands take root, making the nests accessible to predators (Management Plan, 2016). This has been (partly) resolved with the construction of artificial (wooden) platforms for nesting and fences around the colonies (Simeonov, 2011). Recently, five floating platforms for nesting of the protected species were built in the Dalmatian pelican colony, and a 250 m fence was built on the island for protection from predators (RIEW-Ruse 2024; State Party of Bulgaria, 2024).

Abrupt changes in temperature conditions negatively impact species and habitats. Climate change through abnormally high temperatures in winter months (January and February) prompted the birds to start their breeding season too early (State Party of Bulgaria, 2024). Additionally, often later sub zero temperatures occur which lead to forming of ice cover enabling access of predators, affecting Dalmatian Pelican breeding success.
General monitoring of weather conditions is undertaking, but no activity addressing this threat is planned yet (State Party of Bulgaria, 2024)

Deepening the bottom of the Danube causes further disturbance of the water regime and deterioration of the wetland habitats (Birds in Bulgaria 2013). River shipping routes are in close vicinity to the property. Periodic dredging of the river bed is necessary for waterway maintenance (State Party of Bulgaria, 2024). It influences water levels in the river and as a consequence the water balance in the property. Increase of the waterway depth minimizes the probability of river water entering into the property during flood periods and its' duration thus deteriorating water balance of the lake. A 24/7 system monitoring the water level in the lake is active in the property (State Party of Bulgaria, 2024), but no further actions are planned to address this threat.