Forestry in numbers

In 2010, 35% of the Portuguese mainland was covered by forested areas (24). Portuguese forests have undergone significant changes in the past decade, both as a result of the abandonment of agriculture and the consequent transfer of land use to forestry, as well as due to forest fires that have reached huge proportions. Nevertheless, forestry resources play an important role in the national economy.

Maritime pine and eucalypt forest stands and cork oak montado woodland jointly represent 72 % of the forested area and provide the bulk of raw materials for the Portuguese forest-based industry (25). The share of the forestry sector in the national GDP is ca. 2.5 %, which in the European Union is only surpassed by Finland and Sweden. Although forests (broadleaved, coniferous and mixed) are widespread in Portugal, their highest densities occur in central- and south-western Portugal. Forest products (timber, cork, pulp, paper and wooden furniture) represent approximately 10 % of the total Portuguese export. Twentieth century and contemporary trends are large-scale afforestation and vegetation succession following rural abandonment (26). 

Growing stock has been decreasing since 1990, reflecting the severity of forest fires. Annual removals are around 13 million m3 of wood over bark, with 4.8 million m3 of softwoods and 8.5 million m3 of hardwoods (mainly eucalyptus). Cork oak stands produce an average of 120,000 tonnes of cork per year. Forest fires are one of the major threats to forests in the country, especially in the mainland. After two very severe years (2003 and 2005), when the area burnt was very significant, the situation improved and the last three years were considerable better. The number of forest fires also decreased in the last two years, but one has to notice that 70% to 80% of the fires are less than one hectare.

Vulnerabilities - Overview

The increased vulnerability of forests (and people) with respect to climate change refers to several impacts (4,10):

• 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 (2).

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 (4).

Vulnerabilities - Portugal

Climate change may be an important threat to the Portuguese forests. Changes in temperature and precipitation patterns may shift optimal climates for different forest species. Hence, areas that are now climatically suitable for a given species may cease to be or the other way around. It is expected that manifestations of climate change, e.g. increased mortality, will be first apparent in marginal areas, with less favourable conditions, or in degraded forest stands (17). 

In the Iberian Peninsula, forests in eastern Spain and central Portugal in particular are very vulnerable to droughts (27).

There is a tendency that current species are displaced by those which are more tolerant to drought, from south to north and from inland to coastal areas. A rise in temperature may allow species such as cork oak and pine to prosper at higher altitudes expanding their potential distribution. Presently, in more arid areas (for example in inland southern regions), the environmental limits for forest survival may be exceeded; vegetation species better adapted to drought and high temperatures will be favoured by climate change, leading to an increase in biomass productivity in the northern country (with greater incidence in the coastal compared to inland areas).

However, species requiring moisture will have more moderate and localized production; biomass production will experience a moderate decrease in central inland areas. This may be more evident in the south, particularly in inland areas; a greater risk of fires, due to a possible increase in combustible forest biomass and favourable meteorological conditions. This tendency may be enhanced by predicted decreases in productivity.

The impact of climate change on forests may have negative effects on the economy, putting at risk the competitiveness of the industrial forest sector (cellulose, cork, plywood and furniture manufacturing) and the viability of more than 250,000 related work posts. Additionally, degradation and decrease of the productivity of forests puts at risk the sustainability of natural environmental services, such as the regulation of the hydrological cycle, protection against soil erosion, maintenance of biodiversity and its use for recreational purposes.

Cork production

In Portugal, pure and mixed dominant cork oak forests represent 23 % of the total forest area (12) and about 65 % of the world’s cork exports, amounting to an annual export of 845 million € (13). In addition, these forests have important social and environmental values such as providing 19 thousand direct and thousands of indirect workers (e.g., tourism), soil conservation, water cycle regulation, carbon sequestration, and biodiversity protection (14).

Climate change may affect cork oak stands by modifying: (1) tree mortality, (2) tree growth, (3) cork growth, (4) cork quality and (5) complex interactions with pest developments. More frequent droughts and higher temperatures reduce cork growth (15), with direct impacts on cork thickness and the consequent cork production. This calls for changes in oak forest management (16).

The effects of climate change on the management of cork oak forests have been assessed for the period 2010-2100 under the A1B scenario of climate change (using one regional climate model). For the growing season (May–September) in 2100, this scenario includes 33% reduction of precipitation and 2.9°C temperature increase (compared with the reference period 1971–2000) (16).

If current management of oak forests is maintained, climate change may result in 20% decrease in cork production in 2100. Adapted management strategies include reducing debarking intensity (ratio between debarking height and perimeter at breast height measured over cork), extending the interval between cork extractions, and increasing tree density. The first two measures reduce productivity; in combination with higher tree density, however, the negative impact of future climate could be overcome (16). 

Vulnerabilities – Subtropical dry forests in Europe

Subtropical dry forests occur in parts of Europe with at least eight months of over 10°C: parts of Spain, Italy, Greece, and Turkey. These regions have hot dry summers and humid mild winters, with annual rainfall in the 400–900 mm range (2).

Subtropical species are partly already well adapted to warm and dry climates. However, many subtropical species now exist in highly fragmented environments as islands of natural forest amongst oceans of agricultural land. Species at a particular location may not have access to new sites where they would be better adapted to the new climatic conditions. Less tolerant species may then decrease in abundance and hereby create for other, more tolerant resident species opportunities to become more abundant because of reduced competition (2).

Benefits

Globally, based on both satellite and ground-based data, climatic changes seemed to have a generally positive impact on forest productivity since the middle of the 20th century, when water was not limiting (11).

Timber production in Europe

Climate change will probably increase timber production and reduce prices for wood products in Europe. For 2000–2050 a change of timber production in Europe is expected of -4 to +5%. For 2050–2100 an increase is expected of +2 to +13% (3).

Adaptation strategies - Forest management measures in general

Measures such as the establishment of migration corridors, connecting nature reserves, may assist the predicted poleward migration of tree species. Also, forest management should focus on reducing stress from external sources, such as extreme events and disturbances. Some additional management options reported for promoting adaptation are: high-quality genetic selection or selection of trees from specific varieties/origins; promotion of mixed-species forests; decrease of the area of monocultures; reducing the threats of pests and diseases; afforestation; fire prevention (8).

Adaptation strategies - Forest management in Portugal

Changes in stand management can be adopted to counteract the effects of climate change, e.g. lower stand density and fertilization (18), mixed species plantation, uneven age structure, or modified rotation length (19). Forest irrigation (20), even at the earliest growth stages, is generally unfeasible, as water resources in Portugal are already under pressure and will also be threatened by climate change. The most effective adaptation measure will likely reside in the gradual and scientifically based afforestation with the species, sub-species or provenances that better suit the projected future conditions (21). New species for a given region might not necessarily imply the introduction of alien species, but rather replacing existing species with others already growing in the warmest and driest areas of Portugal, i.e. species from southern Portugal can gradually replace existing species in north-western Portugal (17).

In some occasions the most economically relevant species can be substituted by ameliorated hybrids or new genetically bred species that can provide similar economic incomes (22). As key mitigation measures, carbon sequestration policies must also be taken into account in both the selection of species and afforestation planning (17).

Planning a new forest might be regarded as a unique opportunity to transform the Portuguese forest. By following state-of-the-art management practices and avoiding monoculture systems with low biodiversity, forests can become more resilient to climate and climate-induced disturbances such as wildfire, being thus possible to enhance ecosystem services and economic growth (23). Forests with a higher degree of resilience may warrant both the economic competitiveness of an important sector for the Portuguese economy and the environmental benefits of a healthy forest (17). 

Adaptive management

The terms adaptation and adaptive management are often incorrectly used interchangeably. The former involves making adjustments in response to or in anticipation of climate change whereas the latter describes a management system that may be considered, in itself, to be an adaptation tactic (5). Adaptive management is a systematic process for continually improving management policies and practices by learning from the outcomes of operational programmes (6). It involves recognizing uncertainty and establishing methodologies to test hypotheses concerning those uncertainties; it uses management as a tool not only to change the system but to learn about the system (7).

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 (4).

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 (4).

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 (8).

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 (9).

References

The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Portugal.

1. Portuguese Environment Agency with the cooperation of Ecoprogresso – Environment and Development Consultants, SA (2009)
2. Fischlin (ed.) (2009)
3. Karjalainen et al. (2003); Nabuurs et al. (2002); Perez-Garcia et al. (2002); Sohngen et al. (2001), in: Osman-Elasha and Parrotta (2009)
4. Innes (ed.) (2009)
5. Ogden and Innes (2007), in: Innes (ed.) (2009)
6. BCMOF (2006a), in: Innes (ed.) (2009)
7. Holling (1978); Lee (1993, 2001), all in: Innes (ed.) (2009)
8. Roberts (ed.) (2009)
9. Keskitalo (2008), in: Roberts (ed.) (2009)
10. Kirilenko and Sedjo (2007)
11. Boisvenue et al. (2006)
12. AFN (2010), in: Palma et al. (2015)
13. APCOR (2013), in: Palma et al. (2015)
14. Rêgo et al. (2013), in: Palma et al. (2015)
15. Caritat et al. (2000), in: Palma et al. (2015)
16. Palma et al. (2015)
17. Costa et al. (2017)
18. White et al. (2009), in: Costa et al. (2017)
19. Guariguata et al. (2008), in: Costa et al. (2017)
20. Sauer et al. (2010), in: Costa et al. (2017)
21. Aitken et al. (2008), in: Costa et al. (2017)
22. Chhin (2015); McQuillan and Rice (2015), both in: Costa et al. (2017)
23. Afreen et al. (2011), in: Costa et al. (2017)
24. INE (2010), in: Costa et al. (2017)
25. IFN (2013), in: Costa et al. (2017)
26. Fernandes et al. (2014); Loepfe et al. (2010); Moreira et al. (2011), all in: Costa et al. (2017)
27. Bento et al. (2023)