Future climate change could affect the expansion of sub-Mediterranean deciduous forests in Montenegro, both towards the interior and towards higher altitudes. Above the forest and scrub hornbeam underbrush the coastal forests and thickets of black hornbeam and downy oak will spread, while the thermophilic oak forests with black ash would spread towards the inland areas (30).

In the southern and western areas of Montenegro fir stands are particularly threatened. It could disappear from much of its current range in this area. In the areas of high rocks an extinction or reduction of local beech forests is likely to occur. These forests cover smaller or larger areas on the coastal slopes of the Dinaric Alps (Orjen Lovćen, Rumija) above the forest of oak and hornbeam and make the border between the forest communities of the Mediterranean and Eurosiberian-North American region. ... Biologically less valuable species (shrubs hornbeam, oak, ash, etc.) prevent their natural regeneration (30).

The climate zone of coniferous forests is above the belt of beech and fir. The forests of fir and spruce, pure or mixed, occur in very cold subalpine climate, while the communities of endemic-relict whitebark pine and Macedonian pine in warmer enclaves, which are influenced by the Mediterranean climate. These trees are common in the northern area of Montenegro. Predictions are that an increase in temperature and decrease in moisture have the strongest adverse impact on fig and beech, and somewhat less on spruce fir. The reason for this is an express mesophilic character of these species. Additionally, these species are particularly vulnerable to frost. In case of an increase in mean annual temperature for 2 or 3 degrees, the lower limit of climate belts of beech and fir will move from 600 to 750 m or 800 m above sea level (30).

Pests and diseases

Projected weather characteristics (temperature and precipitation) will initiate numerous negative impacts on forest ecosystems and positive impacts on the distribution and physiological state of insects (such as defoliators, bark beetles) and phytopathogenic fungi (e.g. powdery mildew, causers of diseases of fungal assimilation organs and polypore mushrooms). Pests will also extend to the north. Mild winters will provide additionally favorable conditions for their survival through the winter (30).

Timber production

Global and many national timber and wood product markets are not very vulnerable to climate change, due to the size of existing forest inventory (stock of timber), the existence of flexible import and export markets for both stumpage and wood products, and technological change which has contributed greatly to the productivity of existing forests and reduced wood use (32). In countries, such as Montenegro, where the existing timber supply is not utilized very efficiently, improved silvacultural and management practices can compensate for some of the losses in productivity that may occur due to climate change, given the proper economic incentives (31).

Summary of potential physical impacts of climate change on forests in Montenegro (31)

Increases in CO2 concentrations:

• Increase in long-term net primary productivity (NPP) of most trees;
• Differential species impacts that could effect the competition and succession, particularly in mixed forests;
• Unknown interactions with other stressors, but should make trees less vulnerable.

Increases in temperature:

• NPP response depends on where forest species are in relation to their temperature ranges. In the short-run, warming can lengthen growing seasons. Where temperatures are limiting, the impact on NPP will be negative;
• Species can adjust by migration, naturally or managed, but at some point, higher temperatures become limiting to growth over large areas;
• Differential species impacts could effect the competition and succession, particularly in mixed forests;
• Complex effects on other stressors, such as insects and diseases;
• Can interact to limit or enhance CO2 fertilization Increases in vulnerability to forest fires.

Decreases in precipitation:

• NPP response is also dependant on where forest species are in relation to their precipitation ranges (same general types of effects as above).

Increases in magnitude and frequency of extreme events:

• Long-term increases in droughts and floods will probably have a negative impact on NPP. However, forests can adjust their ranges to a certain extent;
• Increases in forests fires will have short- and long term negative consequences on NPP.

Interactions: higher CO2 and higher temperature (1-30°C):

• Generally positive effects on NPP, probably lasting longer than for crops;
• Eventually negative effects on tree growth, but the time frame is uncertain;
• Existing ranges and geographic distribution of species will be altered naturally and/or by human management.

• Forest cover: conversion of forests to non-woody energy plantations; accelerated deforestation and forest degradation; increased use of wood for domestic energy.
• Biodiversity: alteration of plant and animal distributions; loss of biodiversity; habitat invasions by non-native species; alteration of pollination systems; changes in plant dispersal and regeneration.
• Productivity: changes in forest growth and ecosystem biomass; changes in species/site relations; changes in ecosystem nitrogen dynamics.
• Health: increased mortality due to climate stresses; decreased health and vitality of forest ecosystems due to the cumulative impacts of multiple stressors; deteriorating health of forest-dependent peoples.
• Soils and water: changes in the seasonality and intensity of precipitation, altering the flow regimes of streams; changes in the salinity of coastal forest ecosystems; increased probability of severe droughts; increased terrain instability and soil erosion due to increased precipitation and melting of permafrost; more/earlier snow melt resulting in changes in the timing of peak flow and volume in streams. The capacity of the forest ecosystem to purify water is an important service, obviating the cost of expensive filtration plants.
• Carbon cycles: alteration of forest sinks and increased CO2 emissions from forested ecosystems due to changes in forest growth and productivity.
• Tangible benefits of forests for people: changes in tree cover; changes in socio-economic resilience; changes in availability of specific forest products (timber, non-timber wood products and fuel wood, wild foods, medicines, and other non-wood forest products).
• Intangible services provided by forests: changes in the incidence of conflicts between humans and wildlife; changes in the livelihoods of forest-dependent peoples (also a tangible benefit); changes in socio-economic resilience; changes in the cultural, religious and spiritual values associated with particular forests.

Productivity

Increasing CO2 concentration can affect tree growth through increased photosynthetic rates and through improved water-use efficiency. There will be complex interactions, however: forest growth rates may well be increased in some cases by rising levels of atmospheric CO2, but rising temperatures, higher evaporation rates and lower rainfall may lower growth rates in other cases (13).

Non-timber products

Increasingly there are concerns about the productivity of non-timber products such as medicines and foods. Relatively little information is available in the scientific literature about the sustainable management of such products, and even less is known about their vulnerability to climate change (22).

Trends

Most models predict continuing trends of modestly increasing forest productivity in Western Europe over this century (10). Projections for the time near the end of the next century generally suggest decreasing growth and a reduction in primary productivity enhancement as temperatures warm, CO2 saturation is reached for photosynthetic enhancement, and reduced summer precipitation all interact to decrease temperate zone primary productivity (11). The projected increased occurrence of pests, particularly in drought-stressed regions, also contributes to decreased long-term primary productivity in some regions of temperate forests  (12).

Sensitivity to increasing air pollution loads, particularly nitrogen deposition and tropospheric ozone, will impact large areas of the northern temperate forest over the next century. In the temperate domain, air pollution is expected to interact with climate change; while the fertilization effects from nitrogen deposition are still highly uncertain, pollutants such as ozone are known to diminish primary productivity (13).

Migration

The ranges of northern temperate forests are predicted to extend into the boreal forest range in the north and upward on mountains (14). The distribution of temperate broadleaved tree species is typically limited by low winter temperatures (15). Since the latter are projected to rise more rapidly than summer temperatures in Europe and North America, temperate broad-leaved tree species may profit and invade currently boreal areas more rapidly than other temperate species.

Carbon sinks/sources

Temperate forest regions in the highly productive forests of western Europe (16) are known to be robust carbon sinks, although increased temperature may reduce this effect through loss of carbon from soils (17). Weaker carbon sinks or even carbon losses are seen for temperate forests in areas prone to periodic drought, such as southern Europe (18).

Models suggest that the greatest climate change threat to temperate forest ecosystems is reduced summer precipitation, leading to increased frequency and severity of drought (19). This will probably be most prominent in temperate forest regions that have already been characterized as prone to drought stress, such as southern Europe. Drought-stricken forests are also more susceptible to opportunistic pests and fire (20). Together, these related effects can potentially change large areas of temperate forest ecosystems from carbon sinks to sources.

Both the climate and forest ecosystems are constantly changing, and managers will need to adapt their strategies as the climate evolves over the long term. An option that might be appropriate today given expected changes over the next 20 years may no longer be appropriate in 20 years’ time. This will require a continuous programme of actions, monitoring and evaluation – the adaptive management approach described above (22).

There is a widespread assumption that the forest currently at a site is adapted to the current conditions, but this ignores the extent to which the climate has changed over the past 200–300 years, and the lag effects that occur in forests. As a result, replacement of a forest by one of the same composition may no longer be a suitable strategy (22).

Adaptation to climate change has started to be incorporated into all levels of governance, from forest management to international forest policy. Often these policies are not adopted solely in response to climate, and may occur in the absence of knowledge about longer-term climate change. They often serve more than one purpose, including food and fuel provision, shelter and minimizing erosion, as well as adapting to changing climatic conditions (26).

Socio-economic and political conditions have significant influences on vulnerability and adaptive capacity. Climate change projections are perceived by many forest managers as too uncertain to support long-term and potentially costly decisions that may be difficult to reverse. Similarly, uncertainty over future policy developments may also constrain action. Finance is a further barrier to implementing adaptation actions in the forest sector (27).