Bulgaria is a country rich in biodiversity. Climate change events are expected to have different impacts on different types of ecosystems and to affect biodiversity and ecosystem services in a number of ways, including suddenly and even catastrophically. On the other hand, the projected annual increase in average temperatures may contribute to adaptation by extending growing seasons and by species migrating into natural ecosystems, or by the controlled introduction of species for agriculture, green infrastructure or other adaptation purposes.
The main climate change vulnerabilities at different levels of biodiversity and ecosystems in Bulgaria can be summarised as follows:
- Loss of genetic diversity: Genetic diversity is directly threatened by the effects of climate change on vulnerable/endangered species (including endemic species with limited ranges and migration opportunities), which may be lost forever. There are also indirect effects of climate change due to competition for resources between biodiversity and human activities, leading to an increase in other pressures (e.g. water extraction, overexploitation of rare species by vulnerable populations, land use change and fragmentation through infrastructure).
- Disruption of species' life cycles and phenological phases: Climate change can affect the life cycles and breeding periods of species in ecosystems, impacting populations and ecosystem processes (food chains and competition for resources), including through the introduction of invasive species that compete with native species and may displace them from traditional niches, thereby altering ecosystem integrity. Invasive species may also provide opportunities for adaptation to climate change if used as an indicator in an early warning mechanism or if they are commercially important and contribute to the provision of ecosystem services
- Habitat Degradation: a possible consequence of climate change is the degradation of habitats in the Critically Endangered, Endangered, Vulnerable and Near Threatened categories as listed in the Bulgarian Red List of Habitats (BAS, 2011). Habitats at high altitudes in particular are vulnerable to these changes
- Impact on ecosystem service delivery: regime change is a key risk to ecosystem service delivery in the long term. Regime change can go two ways:
- Positive effects: increased length of the growing season can lead to increased productivity of terrestrial ecosystems, including crop and timber yields. Increased temperature can alter conditions in water bodies, which in turn can lead to changes in the composition and structure of fish populations. Disturbances to ecosystems caused by extreme events may also lead to the emergence of new species composition, leading to improved ecosystem service provision
- Negative effects: periods of drought can alter the composition of producers in terrestrial ecosystems, causing changes in their functioning and leading to reduced provision of ecosystem services. Increases in flooding, fire, wind and bark beetle infestations in forests can cause trees to die and be replaced by more adaptive species, as well as changes in ecosystem integrity and potentially a reduction in ecosystem service provision in both the short and medium term (until systems adapt and productivity recovers) or permanently (if the new equilibrium state leads to a reduction in ecosystem service provision). The most vulnerable ecosystems are the forest areas along the southern border, as well as other lowland areas of the country. Inland wetland ecosystems and shrubland ecosystems (especially in the alpine zone in the mountains) and coastal ecosystems are also among the most sensitive to climate change
