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A paradox of planted forests - Increase of goals and commitments is followed by decrease in planting rate!
By Dag Lindgren, Lars Laestadius, and Vladan Ivetić
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Abstract. The role of forests in nature and their importance for human civilization is indisputable. Still we are witnessing a constant loss in global forest cover, land and forest ecosystems degradation. One of the best tool to decrease the magnitude, or even to revert both processes is establishment of new forests, both naturally and artificially by planting. Despite the need to slow down and revert forest cover loss and to restore the land, the global planting rate is decreasing. The purpose for this paper is to look at reasons for this slowing down in more details.
1 Introduction
The role of forests in nature and their importance for human civilization is indisputable. In addition to their role in water cycle, oxygen cycle, and climate regulation, forests provide livelihood for approximately 1.6 billion people, as well as habitat for more than 80% of terrestrial animals, plants, and insects (United Nations 2015). Forest often depends on, but also determine civilization development, with five typical phases of human forest intervention (Persson 2017): Phase 1 - Slow deforestation; Phase 2 - Increasing deforestation usually connected with rapid population growth and increasing demand for forest products; Phase 3 - Forces against deforestation starts to get effect and deforestation slows down; Phase 4 - Forest increase; and Phase 5 - A new equilibrium. Some countries, like Sweden (Persson 2017), reach the phase 5, mainly thanks to planted forest. Hopefully, more of the World will go through the same process, reaching the new equilibrium. A universal turnaround has been detected in many countries of the World from shrinking to expanding forests, with forest resource trends of nations correlate positively with UNDP Human Development Index (Kauppi et al. 2018), indicating that forest resources of nations will improve along with progress in human well-being. This have a further implications, as findings suggest the large sink of carbon recently observed in forests of the World (Song et al. 2018) will increase, if the well-being of people continues to improve.
The importance of forests is undoubtedly crucial, but still we are witnessing a constant loss in global forest cover (Keenan et al. 2015). Another ongoing negative process is land and forest ecosystems degradation. One of the best tool to decrease the magnitude, or even to revert both processes is establishment of new forests, both naturally and artificially by planting. Natural recolonization of deforested areas, abandoned agricultural land, and degraded forest sites is predominantly uncontrolled process and require a long time for late succession. However, even in natural reforestation human intervention is necessary if there is a risk of colonization by unwanted invasive species. Artificial forest establishment by seeding or planting of seedlings provide more control and can bring better results in terms of productivity and sustainability, once when all good practices and theoretical knowledge are applied.
Despite the need to slow down and revert forest cover loss and to restore the land, the global planting rate is decreased in period 2010-2015, compared to previous 20 years (Payn et al. 2015). This finding, and its causes and its consequences, seem remarkable little noticed and discussed, when considering the magnitude of the observed changes. Some years and many opportunities has been missed for deeper analyses to analyse it. The purpose for this paper is to look at these matters in more detail. We started to discuss this at a conference (Lindgren et al. 2018). After that the issue was opened in Reforestation challenge discussion zone (Reforesta 2018). Now we extend the issue as this opinion paper.
2 Do we need more planted forests?
Yes, we do. The usual misperception of planted forests in general public is that they represents a “green deserts”, following the firs association of planted forests to industrial tree plantations. Beside productive component, other components of planted forests are often neglected, even in scientific studies and papers. For example, d’Annunzio et al. (2015) builds their Global Forest Resource Model projection for planted forest area as a function of global wood demand, the changing supply of regional wood production from planted forests and the productivity change foreseen in planted forests. Yet, the planted forests are much more. The concept of planted forests covers a wide range of forest conditions (Zhang and Stanturf 2008, Ivetić and Vilotić 2014), “predominantly composed of trees established through planting and/or through deliberate seeding of native or introduced species. Establishment is either through afforestation on land which has not carried forest within living memory or by reforestation of previously forested land“ (FAO 2010a). Since 2005, in global Forest Resource Assessment, FAO regards to planted forests as a new subgroup, constitutes of plantations (productive and protective) and planted component of semi-natural forests (comprising natural and planted regeneration). The findings of Jürgensen et al. (2014) that, in general, countries of temperate zone (except Spain, Great Britain, and USA) produce more of industrial roundwood in planted component of semi natural forests compared to forest plantations supports our discussion on importance of recognizing of whole spectra of forest conditions regarded as planting forests. Another important aspect of planted forests is opportunity to manipulate range of their environmental benefits with size, species composition and tree density (Cunningham et al. 2015).
In general, we need planted forests to:
In the same time, planted forests meet skepticism and criticism. Indeed, poorly designed and managed, planted forests can have negative social and environmental impacts (Batra and Pirard 2015), affecting valuable landscapes, alienating people from their traditional lands and by disturbing the dynamic and relationships that keep communities and societies together (FAO 2010b). The issues of biodiversity, genetic diversity, and invasiveness also raise the concerns about planted forests. However, all these issues are solvable by proper design and management of planted forests.
The difference between planted forests and natural forests diminish with time, as planted forest provides the similar number and types of ecosystem services to those of natural forests (Baral et al. 2016). How planted forests affect biodiversity can be properly assessed only in context of planting site and neighboring landscape biodiversity status prior the planting and the likely alternative for land-use options for the site (Carnus et al. 2006). Many evidences shows planted forests contributing to biodiversity conservation as a valuable habitat for various species, including threatened and endangered ones (Humpherey et al. 2001, Brockerhoff et al. 2008). Depending on site conditions and goals, different species can be mixed at planting. Species diversity increase the resilience and sustainability of established forest (Larjavaara 2008, Ivetić 2019a), as well as their productivity and wood quality (Tani et al. 2006; Pelleri et al. 2013), because different species use site resources in different ways, resulting with reduced competition and improved utilization of site potential (Ivetić and Devetaković 2017).
The same is with genetic diversity. How much of genetic diversity we need to maintain in the planted forest depends on the management objectives, rotation and the breeding level (Ivetić et al. 2016): with level of breeding the genetic gain rise, but genetic diversity is narrowing, while chances of hazardous situations rise with time. In other words, for planted forests designed, established, and managed for productive purposes in short rotation cycles, one can use forest reproductive material high level of breeding, regardless to narrow genetic diversity, expecting the high gain. Opposite, for planted forests designed, established, and managed for restoration, protective, and conservative purposes in long rotation cycles, one need to use forest reproductive material of high level of genetic diversity. The level of genetic diversity in the new population (i.e. planted forest), depends on several variables with effective size of the seed source population, provenancing and seed collection strategy as the most important ones (Ivetić and Devetaković 2017). In many cases, planted forests are established with use of planting material of unknown origin, but still, the review of papers comparing genetic diversity in natural forests versus various regeneration methods examined by the range of markers (Ivetić and Devetaković 2017), in most cases found no significant differences in genetic diversity between natural and planted forests, followed by an almost equal number of cases with decreased and increased level of genetic diversity.
Finally, there are concerns related to use of non-native genes (species and provenances) which can be invasive. The introduction of new genes is an usual practice in planting of new forests, due to higher productivity of non-local provenances (Schmidtling and Myszewski 2003; Ivetić et al. 2005; Krakowski and Stoehr 2009) and non-native species (Heryati et al. 2011; Kawaletz et al. 2013; Guo and Ren 2014b; Kjær et al. 2014, Ivetić 2017) compared to local (native) populations at a specific site. Although FAO FRA 2015 shows that, at global level, only 18-19% of planted forests are of introduced species, which dominates at southern hemisphere (Payn et al. 2015), in many parts of the world, non-native tree species are among the most conspicuous and damaging invasive alien plants (Brundu and Richardson 2016). Again, the risk of invasive species can be reduced to minimum with proper plantation forests management.
The true is that area of planted forests, regardless to definition and purpose, will continue to rise as it was in previous thousands of years. Blaser and Gregersen (2013) predicted for year 2313 “3 billion ha of intensively managed planted and assisted natural regeneration forests, of which about 2 billion hectares will be planted forests for the production of wood and non-wood goods and services”. Yet, the question remain are we plant enough trees (for production, protection, restoration, assisted regeneration) to slow down the negative trends of forest loss and to increase the socio-economic and ecological benefits of planted forests.
3 Commitments and goals
There are many large scale initiatives and programs for reforestation and restoration at global, regional, and national level (Ivetić 2019b, Table 1) – all relay, to some extent, on tree planting and establishment of planted forests. The substantially increase of afforestation and reforestation globally is part of Global Forest Goal 1 of United Nations strategic plan for forests 2017-2030 (UN 2017).
Table 1. The ongoing large scale reforestation programs and initiatives
All these commitments and goals leads Andrew Steer, The President and CEO of World Resources Institute and Mark Tercek, The President and CEO of The Nature Conservancy to conclude that there has never been a better time to invest in land restoration, due to increased demand for businesses that can deliver large projects cost-effectively (the foreword of Faruqi et al. 2018).
4 Trend of planted forests
Although FAO started to collect data on plantation forests since 1980, the statistics of planted forests in unclear, due to differences and changes in concept, definition and methodology.
Figure 1. Global area of planted forests from 1970 to 2015 according to the different sources
The first global estimation was given for the early 1970’s by Persson (1974) regarding the man-made forests, saying that “For the whole world the area may be around 100 million ha”. There are many different assessments of planted forest area in 1980 (Figure 1), ranging from 17.8 million of hectares (Carle et al. 2002) and 28.9 million of hectares (FAO 1988) to 85-105 million of hectares (FAO 1997: “a rough estimate of the total forest plantation in” developed countries “45-60 million ha in 1980”, plus 40 million hectares in developing countries). For year 1990 there is estimated 43.6 million of hectares (Carle et al. 2002) and 209 million of hectares (FAO 2006). For year 1995 there is estimated 161-181 million hectares (FAO 1997) and 124 million hectares (FRA 2000). Global area of planted forests in year 2000 was estimated on 187 million hectares (FAO 2000, Carle et al. 2002) and 246 million of hectares (FAO 2006). Global area of planted forests in year 2005 was estimated on 271 million hectares (FAO 2006) and in year 2010 it was estimated on 264 million hectares (FAO 2010). Finally, in year 2015 the global area of planted forests was estimated on 291 million hectares (Figure 1).
Figure 2. Global annual increase of planted forests in millions of hectares (bars) and in percent (lines)
The first global report on planting efforts is given in world forest resources inventory undertaken in 1953 by the Forestry Division of FAO (FAO 1957). During the six years period (1947-1952) 2.65 million of hectares of bare land was planted, in 83 countries for which data was available. The available data indicate that planting efforts was much larger in the following five-year period (1953-1957) with afforested area 3.95 million hectares reported from 70 countries (FAO 1960). During 1960’s and 1970’s there was no reports on global planting efforts. However, the World Forest Inventory 1963 shows that many countries reported very large areas of forest land, but up to 50% was unstocked, indicating these area to be planted in the future. Yet, at very beginning there was a little faith in success: “some countries also included land that has not previously borne forest, but is planned for afforestation” but “It appears that reforestation "in the foreseeable future" is intended in many areas which are likely to remain without forest for some decades” (FAO 1963). Again, during 1980’s there was no global assessments run by FAO. Because of that, for period 1980-1990 (Figure 2) we used assessment from Forest Resources Assessment 1990 (FAO 1995) which, unfortunately, reports data only for developing countries with annual planting rate of 4,1 million hectares. This planting rate is much higher than increase in global forest plantation estate from 17.8 million hectares in 1980 to 43.6 million hectares in 1990 (Carle et al. 2002), which gives annual rate of 2.58 million hectares. This difference is even larger for period 1990-2000, with increase in global forest plantation form 43.6 million hectares in 1990 to 187 million hectares in 2000 (Carle et al. 2002), which gives the annual rate of 14,3 million hectares. Such a huge increase in global forest plantation estate during 1990’s can be explained, to some extent, by large increase in plantation area in Asia and North and Central America, and the fact that there was no plantations reported in Europe in 1990, but 32 million of hectares in 2000 (see Table 4 in Carle et al. 2002). For the same period (1990-2000) due to change in definition of planted forests and estimation for year 1990 according to the new definition, the more realistic estimation is given in FAO (2006) with increase of 1.6%, at annual planting rate of 3.7 million of hectares (Figure 2). For period 2000-2005 area of planted forests increased by 1.9% with annual planting rate of 4.9 million of hectares (FAO 2006).
5 Reasons for slowing down: Why the global planting rate is slowing down? or Is it slowing down at all?
Causes and consequences of reduced new forests and planting are not well discussed. Payn et al. (2015) comment shortly without an extended discussion: “the annualised rate of increase in area of planted forests slowed in the 2010–2015 period to 1.2%, below the 2.4% rate suggested is needed to supply all of the world’s timber and fibre needs.” The FAO documents mentions the reduced new forest very shortly and not at all its causes and consequences. The latest from FAO is:” The state of the world´s forests 2018” (FAO 2018a) in different versions. The complete version (119 p) mentions plantations from two countries and planted forest for one. It recognizes shortly the recent drop without discussing causes or consequences. The short version booklet is said to contain the key messages but plantation (=planted forests) is mentioned only once and that is description of national plans in a single country. FAO (2018b) prizes the forest in a multitude of ways but does not mention planted forest and warns for cutting trees.
Some key deadlines are looming, the strategies are not always backed by evidence, and measures of success are still being defined. But quantification of these factors as an explanation of the worldwide reduction of new planted forest is lacking.
Wagner (2005) offered a potential causes for decrease in artificial regeneration in North America after 1990, with reduced commitment by landowners to pay and less advocacy by foresters for artificial regeneration, following the paradigm shift, as the most likely ones. Paradigm shifts causes the changes in plantation forestry and planting efforts are strongly linked to the general historical and economic developments (Szulecka et al. 2014).
The causes of slowing down of global planting, in reality and/or in paper, are:
• Definition issues - Definition of planted forests changes over the time, with changes in purpose of data collection and with changes in management goal (see Chazdon et al. 2016 and Ivetić 2019 for more detailed discussion). These changes in definition are reason for differences in estimation of planted forests area and trends (see Table 1 and 2).
“The Bonn initiative” has resulted in Global Landscapes Forum. The Bonn Challenge sets restoration high on the global policy agenda with the goal of bringing 150 million hectares of the world’s deforested and degraded land into restoration by 2020 (Global Landscape Forum 2018, Bonnchallenge 2018). But variants of “plant…” are seldom mentioned. The Bonn-initiative also resulted in: “The Bonn Challenge (Bonnchallenge 2018) is a global effort to restore 150 million hectares of the world's degraded and deforested lands by 2020. It is overseen by the Global Partnership on Forest Landscape Restoration. Our impression is that landscape restoration avoids mentioning new forest and afforestation. But there are exceptions when coming down to individual programs. IUCN describes that Pakistan has started a Billion Tree Tsunami Afforestation Project in Pakistan’s northern Khyber Pakhtunkhwa (KPK) province has surpassed its target by restoring and planting trees in 350,000 hectares of degraded forest landscapes. That’s fine but only 2 permille of the global target! The project has achieved its restoration target through a combination of protected natural regeneration (60%) and planned afforestation (40%). In addition, it has established 13,000 private tree nurseries, which have already boosted local incomes, generated thousands of green jobs, and empowered unemployed youth and women in the province. Falk et al. (2018) gives a recipe for halving world’s climate gas releases till 2030 including planting new forests: “Massive reforestation and afforestation campaigns combined with protecting and restoring existing forests, will play a major role in cutting emissions in half by 2030. It will also create major new carbon storage capacity.” Nevertheless, the “REDD” (Reducing Emissions from Deforestation and forest Degradation) process has been going on for the last decade, and its implementation seems to coincide with the decrease in planted forests, but little discussed.
The world cumulative planted forest was 278 Mha 2015 (Payn et al 2015) Forty percent afforestation for worldwide BonnChallenge means annually 0.4*350/(2030-2015)= 9Mha planted forest/year = 3.3% annual increase. The required annual afforested area is similar to what is required to meet the UN strategic target (UN 2017) providing if no forest loss occurs somewhere (completely unrealistic!). The envisioned need for afforestation is almost three times the annual increase of new forest 2010-2015 pointing out that more efforts is really needed on establishing planted forests.
At 3rd Restoring Forest Conference Stanturf (2017) warned for risks for the restoration initiatives: 1) diminishing of policy-makers interest when facing the cost and complexity, 2) fail of restoration initiatives to deliver on expectations, and 3) high cost of achieving meaningful restoration success. Probably factors like these contribute to explaining the observed recent drop in new planted forest.
6 Conclusions
The questions of why and are global forest planting slow down at all, are hard to answer. However, errors and uncertainties in statistics do not change our rhetoric for more planted forest. Even if the exact values are uncertain, the remarkable drop in new forest 2005-2015 is too large to rule out uncertainties or factors which has not changed drastically and globally recently as a major cause. We feel certain that more planted forest is a tool for a better world, but conditions vary. Yet, planting forest instead of trusting in nature generally requires better knowledge and competence as well as reasonable stable organization and economy and trust in the politics.
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Zhang D, Stanturf JA (2008) Forest Plantations. In Jørgensen SE and FathBD (Editors-in-Chief), Ecosystems. Vol. [2] of Encyclopedia of Ecology, Oxford: Elsevier 5: 1673-1680.
1 Introduction
The role of forests in nature and their importance for human civilization is indisputable. In addition to their role in water cycle, oxygen cycle, and climate regulation, forests provide livelihood for approximately 1.6 billion people, as well as habitat for more than 80% of terrestrial animals, plants, and insects (United Nations 2015). Forest often depends on, but also determine civilization development, with five typical phases of human forest intervention (Persson 2017): Phase 1 - Slow deforestation; Phase 2 - Increasing deforestation usually connected with rapid population growth and increasing demand for forest products; Phase 3 - Forces against deforestation starts to get effect and deforestation slows down; Phase 4 - Forest increase; and Phase 5 - A new equilibrium. Some countries, like Sweden (Persson 2017), reach the phase 5, mainly thanks to planted forest. Hopefully, more of the World will go through the same process, reaching the new equilibrium. A universal turnaround has been detected in many countries of the World from shrinking to expanding forests, with forest resource trends of nations correlate positively with UNDP Human Development Index (Kauppi et al. 2018), indicating that forest resources of nations will improve along with progress in human well-being. This have a further implications, as findings suggest the large sink of carbon recently observed in forests of the World (Song et al. 2018) will increase, if the well-being of people continues to improve.
The importance of forests is undoubtedly crucial, but still we are witnessing a constant loss in global forest cover (Keenan et al. 2015). Another ongoing negative process is land and forest ecosystems degradation. One of the best tool to decrease the magnitude, or even to revert both processes is establishment of new forests, both naturally and artificially by planting. Natural recolonization of deforested areas, abandoned agricultural land, and degraded forest sites is predominantly uncontrolled process and require a long time for late succession. However, even in natural reforestation human intervention is necessary if there is a risk of colonization by unwanted invasive species. Artificial forest establishment by seeding or planting of seedlings provide more control and can bring better results in terms of productivity and sustainability, once when all good practices and theoretical knowledge are applied.
Despite the need to slow down and revert forest cover loss and to restore the land, the global planting rate is decreased in period 2010-2015, compared to previous 20 years (Payn et al. 2015). This finding, and its causes and its consequences, seem remarkable little noticed and discussed, when considering the magnitude of the observed changes. Some years and many opportunities has been missed for deeper analyses to analyse it. The purpose for this paper is to look at these matters in more detail. We started to discuss this at a conference (Lindgren et al. 2018). After that the issue was opened in Reforestation challenge discussion zone (Reforesta 2018). Now we extend the issue as this opinion paper.
2 Do we need more planted forests?
Yes, we do. The usual misperception of planted forests in general public is that they represents a “green deserts”, following the firs association of planted forests to industrial tree plantations. Beside productive component, other components of planted forests are often neglected, even in scientific studies and papers. For example, d’Annunzio et al. (2015) builds their Global Forest Resource Model projection for planted forest area as a function of global wood demand, the changing supply of regional wood production from planted forests and the productivity change foreseen in planted forests. Yet, the planted forests are much more. The concept of planted forests covers a wide range of forest conditions (Zhang and Stanturf 2008, Ivetić and Vilotić 2014), “predominantly composed of trees established through planting and/or through deliberate seeding of native or introduced species. Establishment is either through afforestation on land which has not carried forest within living memory or by reforestation of previously forested land“ (FAO 2010a). Since 2005, in global Forest Resource Assessment, FAO regards to planted forests as a new subgroup, constitutes of plantations (productive and protective) and planted component of semi-natural forests (comprising natural and planted regeneration). The findings of Jürgensen et al. (2014) that, in general, countries of temperate zone (except Spain, Great Britain, and USA) produce more of industrial roundwood in planted component of semi natural forests compared to forest plantations supports our discussion on importance of recognizing of whole spectra of forest conditions regarded as planting forests. Another important aspect of planted forests is opportunity to manipulate range of their environmental benefits with size, species composition and tree density (Cunningham et al. 2015).
In general, we need planted forests to:
- slow down and to reduce forest cover loss - “Although regeneration activity is not a measure of regeneration success, it is an index of commitment to successful reforestation and afforestation” (Wagner 2005). If we want to slow down or even to revert forest loss, we need to plant more. Each year we cut down over 15 billion trees, resulting with reduction of global number of trees for approximately 46% since the start of human civilization (Crowther et al. 2015). Although the annual rate of net forest loss is reduced by 55% since 1990s, we still lose approximately 3.3 million of hectares each year (Keenan et al. 2015). This estimate based on FAO Forest Resource Assessment methodology is considerable below recent global estimates based on satellite information (Curtis et al. 2018).
- restore a degraded ecosystems - Establishment of planted forests is an important component of functional reforestation and play a key role in forest restoration strategies, such as: rehabilitation, reconstruction, reclamation and replacement (Stanturf et al. 2014). It is estimated that over two billion hectares of the world’s deforested and degraded forest lands contain (so conveniently called) opportunities for restoration (WRI 2014). However, not all of these areas are suitable for forest restoration only, as 9 million square kilometers of ancient grassy biomes misidentified as opportunity for forest restoration (Veldman et al. 2015).
- reduce the pressure on existing natural forests - As more productive, planted forests has a large share of the worlds industrial roundwood production and will probably soon dominate! Planted forests, contributing only 6.95% in total forest area, have a potential to produce over 65% of global industrial roundwood demand, with possible increase up to 80% by 2030 (Carle and Holmgren 2008). Yet, in 2012 forest plantations provided only one third the real global demand for industrial roundwood (0.52 billion m3 production compared to demand of over a 1.5 billion m3, INDUFOR 2012). The same share of 33% is reported in assessment of industrial roundwood production from planted forests in 2012, originating from plantations in 78 countries (Jürgensen et al. 2014). However, the authors suggested that this share is underestimated, because data was not available for a number of countries that have reported a significant area of planted forest. In addition, the results of FAO FRA 2015 indicates that planted forests did not reach their production maximum in all countries (Payn et al. 2015). The share will rise, as in some important countries with much planted forest it takes long time before planting is evident in harvest statistics. E.g. in Sweden probably less than half of the current harvest is from planted trees although more than 80% of current reforestation is by planting. Although the National Forest Inventory in Serbia (Banković et al. 2009) shows that average volume in planted forests (127 m3 ha-1 in cultures and 172 m3 ha-1 in industrial plantations) is much lower than in natural high forests (254 m3 ha-1), mainly because of lower age classes, the annual volume increase in planted forests is much higher (6,5 m3 ha-1 in cultures and 9,0 m3 ha-1 in industrial plantations) compared to natural regenerated high forests (5,5 m3 ha-1) and coppice forests (3,1 m3 ha-1), indicating their higher productivity (Ivetić and Vilotić 2014). The oldest experimental comparison between clear-cutting followed by planting and natural regeneration (“untouched unmanaged” forest), established in 1923 in central Sweden, shows that after 85 years the clear-cut and planted plot had around 50% more growing stock and faster growth (Lundqvist et al. 2013). Planted forests are more productive compared to natural forests, and their productivity can be additionally increased by different practices (selection of forest reproductive material, breeding, silviculture, protection, etc.). As more productive, planted forests reduce prices of forest (24-37%) and wood products (4-14%), and in same time increase world production of fuelwood (4%) and industrial roundwood (14%), but more important, utilization of planted forests reduce harvest of roundwood from natural forests by one quarter (Buongiorno et al. 2014).
- to promote sustainable development - As important source of various forest products and services, and a vital resource for future green economies (ICPF 2013), planted forests of good design and management can contribute to sustainable development by supporting livelihood and standard of rural communities (FAO 2010b). Planting opens the floor for forest tree breeding. Domestication/breeding success for agricultural crops and husbandry was the cradle for civilization and is still a fundamental pillar. Tree breeding makes the seed (clone) source better defined, more reproducible, and can add much to the value of the forest. The global impact of tree breeding is hardly known. To our knowledge, no single country has specified the cumulative forest area forested with bred material of different categories, this information is only available for specific programs. Only FAO can ask the right questions and get replies on questions in a comparable format. These could be compiled as reasonable global estimates of the use and impact of tree breeding. The well-defined and known seed sources tree breeding creates and facilitates adaptation the forest to present and foreseen climate changes.
- to regulate the climate and to mitigate the climate change – Although plantations in China aged 0–80 years have similar biomass as natural forests growing in similar physical conditions, they have a much higher productivity and carbon sequestration rates (Guo and Ren 2014a). In addition to estimated 2 giga tonnes of carbon sequestered by 271 million hectares of planted forests all over the world every year (1.5 giga tonnes in biomass plus 0.5 giga tonnes stored long-term in forest products (Carle and Holmgren 2008), planted forests provide wood and woody biomass as a replacement for fossil fuels, or as a replacement for energy-intensive materials used in construction and other industries (Silva et al. 2018). Forestation from 2000 to 2010 caused cooling in tropical (-0.18°C) and and temperate (-0.19°C) regions (Prevedello et al. 2019).
In the same time, planted forests meet skepticism and criticism. Indeed, poorly designed and managed, planted forests can have negative social and environmental impacts (Batra and Pirard 2015), affecting valuable landscapes, alienating people from their traditional lands and by disturbing the dynamic and relationships that keep communities and societies together (FAO 2010b). The issues of biodiversity, genetic diversity, and invasiveness also raise the concerns about planted forests. However, all these issues are solvable by proper design and management of planted forests.
The difference between planted forests and natural forests diminish with time, as planted forest provides the similar number and types of ecosystem services to those of natural forests (Baral et al. 2016). How planted forests affect biodiversity can be properly assessed only in context of planting site and neighboring landscape biodiversity status prior the planting and the likely alternative for land-use options for the site (Carnus et al. 2006). Many evidences shows planted forests contributing to biodiversity conservation as a valuable habitat for various species, including threatened and endangered ones (Humpherey et al. 2001, Brockerhoff et al. 2008). Depending on site conditions and goals, different species can be mixed at planting. Species diversity increase the resilience and sustainability of established forest (Larjavaara 2008, Ivetić 2019a), as well as their productivity and wood quality (Tani et al. 2006; Pelleri et al. 2013), because different species use site resources in different ways, resulting with reduced competition and improved utilization of site potential (Ivetić and Devetaković 2017).
The same is with genetic diversity. How much of genetic diversity we need to maintain in the planted forest depends on the management objectives, rotation and the breeding level (Ivetić et al. 2016): with level of breeding the genetic gain rise, but genetic diversity is narrowing, while chances of hazardous situations rise with time. In other words, for planted forests designed, established, and managed for productive purposes in short rotation cycles, one can use forest reproductive material high level of breeding, regardless to narrow genetic diversity, expecting the high gain. Opposite, for planted forests designed, established, and managed for restoration, protective, and conservative purposes in long rotation cycles, one need to use forest reproductive material of high level of genetic diversity. The level of genetic diversity in the new population (i.e. planted forest), depends on several variables with effective size of the seed source population, provenancing and seed collection strategy as the most important ones (Ivetić and Devetaković 2017). In many cases, planted forests are established with use of planting material of unknown origin, but still, the review of papers comparing genetic diversity in natural forests versus various regeneration methods examined by the range of markers (Ivetić and Devetaković 2017), in most cases found no significant differences in genetic diversity between natural and planted forests, followed by an almost equal number of cases with decreased and increased level of genetic diversity.
Finally, there are concerns related to use of non-native genes (species and provenances) which can be invasive. The introduction of new genes is an usual practice in planting of new forests, due to higher productivity of non-local provenances (Schmidtling and Myszewski 2003; Ivetić et al. 2005; Krakowski and Stoehr 2009) and non-native species (Heryati et al. 2011; Kawaletz et al. 2013; Guo and Ren 2014b; Kjær et al. 2014, Ivetić 2017) compared to local (native) populations at a specific site. Although FAO FRA 2015 shows that, at global level, only 18-19% of planted forests are of introduced species, which dominates at southern hemisphere (Payn et al. 2015), in many parts of the world, non-native tree species are among the most conspicuous and damaging invasive alien plants (Brundu and Richardson 2016). Again, the risk of invasive species can be reduced to minimum with proper plantation forests management.
The true is that area of planted forests, regardless to definition and purpose, will continue to rise as it was in previous thousands of years. Blaser and Gregersen (2013) predicted for year 2313 “3 billion ha of intensively managed planted and assisted natural regeneration forests, of which about 2 billion hectares will be planted forests for the production of wood and non-wood goods and services”. Yet, the question remain are we plant enough trees (for production, protection, restoration, assisted regeneration) to slow down the negative trends of forest loss and to increase the socio-economic and ecological benefits of planted forests.
3 Commitments and goals
There are many large scale initiatives and programs for reforestation and restoration at global, regional, and national level (Ivetić 2019b, Table 1) – all relay, to some extent, on tree planting and establishment of planted forests. The substantially increase of afforestation and reforestation globally is part of Global Forest Goal 1 of United Nations strategic plan for forests 2017-2030 (UN 2017).
Table 1. The ongoing large scale reforestation programs and initiatives
All these commitments and goals leads Andrew Steer, The President and CEO of World Resources Institute and Mark Tercek, The President and CEO of The Nature Conservancy to conclude that there has never been a better time to invest in land restoration, due to increased demand for businesses that can deliver large projects cost-effectively (the foreword of Faruqi et al. 2018).
4 Trend of planted forests
Although FAO started to collect data on plantation forests since 1980, the statistics of planted forests in unclear, due to differences and changes in concept, definition and methodology.
Figure 1. Global area of planted forests from 1970 to 2015 according to the different sources
The first global estimation was given for the early 1970’s by Persson (1974) regarding the man-made forests, saying that “For the whole world the area may be around 100 million ha”. There are many different assessments of planted forest area in 1980 (Figure 1), ranging from 17.8 million of hectares (Carle et al. 2002) and 28.9 million of hectares (FAO 1988) to 85-105 million of hectares (FAO 1997: “a rough estimate of the total forest plantation in” developed countries “45-60 million ha in 1980”, plus 40 million hectares in developing countries). For year 1990 there is estimated 43.6 million of hectares (Carle et al. 2002) and 209 million of hectares (FAO 2006). For year 1995 there is estimated 161-181 million hectares (FAO 1997) and 124 million hectares (FRA 2000). Global area of planted forests in year 2000 was estimated on 187 million hectares (FAO 2000, Carle et al. 2002) and 246 million of hectares (FAO 2006). Global area of planted forests in year 2005 was estimated on 271 million hectares (FAO 2006) and in year 2010 it was estimated on 264 million hectares (FAO 2010). Finally, in year 2015 the global area of planted forests was estimated on 291 million hectares (Figure 1).
Figure 2. Global annual increase of planted forests in millions of hectares (bars) and in percent (lines)
The first global report on planting efforts is given in world forest resources inventory undertaken in 1953 by the Forestry Division of FAO (FAO 1957). During the six years period (1947-1952) 2.65 million of hectares of bare land was planted, in 83 countries for which data was available. The available data indicate that planting efforts was much larger in the following five-year period (1953-1957) with afforested area 3.95 million hectares reported from 70 countries (FAO 1960). During 1960’s and 1970’s there was no reports on global planting efforts. However, the World Forest Inventory 1963 shows that many countries reported very large areas of forest land, but up to 50% was unstocked, indicating these area to be planted in the future. Yet, at very beginning there was a little faith in success: “some countries also included land that has not previously borne forest, but is planned for afforestation” but “It appears that reforestation "in the foreseeable future" is intended in many areas which are likely to remain without forest for some decades” (FAO 1963). Again, during 1980’s there was no global assessments run by FAO. Because of that, for period 1980-1990 (Figure 2) we used assessment from Forest Resources Assessment 1990 (FAO 1995) which, unfortunately, reports data only for developing countries with annual planting rate of 4,1 million hectares. This planting rate is much higher than increase in global forest plantation estate from 17.8 million hectares in 1980 to 43.6 million hectares in 1990 (Carle et al. 2002), which gives annual rate of 2.58 million hectares. This difference is even larger for period 1990-2000, with increase in global forest plantation form 43.6 million hectares in 1990 to 187 million hectares in 2000 (Carle et al. 2002), which gives the annual rate of 14,3 million hectares. Such a huge increase in global forest plantation estate during 1990’s can be explained, to some extent, by large increase in plantation area in Asia and North and Central America, and the fact that there was no plantations reported in Europe in 1990, but 32 million of hectares in 2000 (see Table 4 in Carle et al. 2002). For the same period (1990-2000) due to change in definition of planted forests and estimation for year 1990 according to the new definition, the more realistic estimation is given in FAO (2006) with increase of 1.6%, at annual planting rate of 3.7 million of hectares (Figure 2). For period 2000-2005 area of planted forests increased by 1.9% with annual planting rate of 4.9 million of hectares (FAO 2006).
5 Reasons for slowing down: Why the global planting rate is slowing down? or Is it slowing down at all?
Causes and consequences of reduced new forests and planting are not well discussed. Payn et al. (2015) comment shortly without an extended discussion: “the annualised rate of increase in area of planted forests slowed in the 2010–2015 period to 1.2%, below the 2.4% rate suggested is needed to supply all of the world’s timber and fibre needs.” The FAO documents mentions the reduced new forest very shortly and not at all its causes and consequences. The latest from FAO is:” The state of the world´s forests 2018” (FAO 2018a) in different versions. The complete version (119 p) mentions plantations from two countries and planted forest for one. It recognizes shortly the recent drop without discussing causes or consequences. The short version booklet is said to contain the key messages but plantation (=planted forests) is mentioned only once and that is description of national plans in a single country. FAO (2018b) prizes the forest in a multitude of ways but does not mention planted forest and warns for cutting trees.
Some key deadlines are looming, the strategies are not always backed by evidence, and measures of success are still being defined. But quantification of these factors as an explanation of the worldwide reduction of new planted forest is lacking.
Wagner (2005) offered a potential causes for decrease in artificial regeneration in North America after 1990, with reduced commitment by landowners to pay and less advocacy by foresters for artificial regeneration, following the paradigm shift, as the most likely ones. Paradigm shifts causes the changes in plantation forestry and planting efforts are strongly linked to the general historical and economic developments (Szulecka et al. 2014).
The causes of slowing down of global planting, in reality and/or in paper, are:
• Definition issues - Definition of planted forests changes over the time, with changes in purpose of data collection and with changes in management goal (see Chazdon et al. 2016 and Ivetić 2019 for more detailed discussion). These changes in definition are reason for differences in estimation of planted forests area and trends (see Table 1 and 2).
- Methodology issues – regarding data collection and period of time for trend estimation. The quality of data collected by FAO depends on quality of response. Since Forest resources of the World (FAO 1948) which reports results for the World Forest Inventory 1947, global forest resource assessment depends on government responses to the questionnaire and the country reports. Some of which, because of various reasons can underestimate or overestimate planting efforts. The methodology issues and their implications are well discussed by Busch (2015), who emphasize that a global statistics require data of uniform quality, consistent through time and comparable across the space, not “the jumble of national statistics in FRA”. The time period for trend estimation also affect the results and conclusions. The longer period for trend estimation eliminates some reasons for variation and makes the decline a little less dramatic. Rather few countries dominate planted forest including fresh new forest plantation statistics and their reports vary between occurrences. Probably some reasons, other that real changes, may cause difference between countries and periods, indicating that decrease in global annual planting rate in period 2010-2015 may be a bit low by “stochastic” variation. Methodology and reporting on new areas under planted forests from national authorities also can be a reason for difference between periods, because it is noticed that some countries reported all areas planted in previous decades in one assessment period, and then continuing to report the real planted areas in following periods (see Ivetić and Devetaković 2016). A few countries are close to saturated with planted forest so new planted forests decline, but that seems unlikely to be common considering that only 7% of the Worlds forest are planted. As the FAO FRA 2015 was updated 2016 (FAO 2016), it is unlikely most late or formally inadequate reporting from some countries has not been mended. Recent net loss in tropics may be overestimated because old data, over-reliance of satellite information with insufficient ground inventory, and the political machinery of reporting. Area of planted forest is not estimable from satellite-data, and at least partly depending on inventories on ground. The drastic drop in new forest 2010-2015 may be smaller than estimated and the new forest 2000-2005 overestimated for some reason, although we have not seen a trustworthy explanation.
- Practical issues - To meet the goals and to fulfill commitments require a huge amount of good quality forest reproductive material – seeds and seedlings. “Meeting forest restoration challenges relies on successful establishment of plant materials” (Dumroese et al. 2016). Although direct seeding is being reconsidered as a restoration option to meet a growing size of the worldwide forest restoration program, planting of seedlings is still proven to be a better way to success (Grossnickle and Ivetić 2016). In addition to natural regeneration and direct seeding, planting of seedling is going to have a huge share in afforestation, reforestation, and forest restoration (and of course in plantation forestry). The good example of amount of seedlings needed is given by Haase and Davis (2017): “meeting the expanded Bonn Challenge of 350 x 106 (million) hectares restored by 2030 at a target density of 500 plants per hectare would require establishment of 175 x 109 (billion) plants. Assuming a relatively high survival rate of 80% means that nearly 220 x 109 plants would need to be outplanted (roughly 18.3 x 109 seedlings per year during the 12 years until 2030).” Production of enough reproductive material of a good quality for ambitious reforestation and forest restoration programs is just one among following challenges and perspectives recognized at Conference on Reforestation challenges held in Belgrade 2018 (Ivetić 2018): uncertainty of environmental changes, neglected significance of nursery production, the establishment phase of seedling establishment will become more critical in the future at some sites, changing environments brings new challenges to the traditional silvicultural approaches, and facing the failure. Following the establishment, the silviculture and management of planted forests is crucial for success.
- Political issues – As it is mentioned in the methodological issues discussed above, statistics is both difficult and politically influenced. Another potential reason for slowing down of global planting efforts is facing the true. The business interests will drive the process of increase of the most productive component of planted forests, i.e. industrial tree plantations, but more political will, organizational skills, and financial support are required to increase area of non-productive planted forests. Currently, forest landscape restoration is between discovery/enthusiasm and realization of costs phases of policy attention cycle, which are usually followed by decline of interest and enthusiasm gap (Stanturf et al. 2019).
“The Bonn initiative” has resulted in Global Landscapes Forum. The Bonn Challenge sets restoration high on the global policy agenda with the goal of bringing 150 million hectares of the world’s deforested and degraded land into restoration by 2020 (Global Landscape Forum 2018, Bonnchallenge 2018). But variants of “plant…” are seldom mentioned. The Bonn-initiative also resulted in: “The Bonn Challenge (Bonnchallenge 2018) is a global effort to restore 150 million hectares of the world's degraded and deforested lands by 2020. It is overseen by the Global Partnership on Forest Landscape Restoration. Our impression is that landscape restoration avoids mentioning new forest and afforestation. But there are exceptions when coming down to individual programs. IUCN describes that Pakistan has started a Billion Tree Tsunami Afforestation Project in Pakistan’s northern Khyber Pakhtunkhwa (KPK) province has surpassed its target by restoring and planting trees in 350,000 hectares of degraded forest landscapes. That’s fine but only 2 permille of the global target! The project has achieved its restoration target through a combination of protected natural regeneration (60%) and planned afforestation (40%). In addition, it has established 13,000 private tree nurseries, which have already boosted local incomes, generated thousands of green jobs, and empowered unemployed youth and women in the province. Falk et al. (2018) gives a recipe for halving world’s climate gas releases till 2030 including planting new forests: “Massive reforestation and afforestation campaigns combined with protecting and restoring existing forests, will play a major role in cutting emissions in half by 2030. It will also create major new carbon storage capacity.” Nevertheless, the “REDD” (Reducing Emissions from Deforestation and forest Degradation) process has been going on for the last decade, and its implementation seems to coincide with the decrease in planted forests, but little discussed.
The world cumulative planted forest was 278 Mha 2015 (Payn et al 2015) Forty percent afforestation for worldwide BonnChallenge means annually 0.4*350/(2030-2015)= 9Mha planted forest/year = 3.3% annual increase. The required annual afforested area is similar to what is required to meet the UN strategic target (UN 2017) providing if no forest loss occurs somewhere (completely unrealistic!). The envisioned need for afforestation is almost three times the annual increase of new forest 2010-2015 pointing out that more efforts is really needed on establishing planted forests.
At 3rd Restoring Forest Conference Stanturf (2017) warned for risks for the restoration initiatives: 1) diminishing of policy-makers interest when facing the cost and complexity, 2) fail of restoration initiatives to deliver on expectations, and 3) high cost of achieving meaningful restoration success. Probably factors like these contribute to explaining the observed recent drop in new planted forest.
6 Conclusions
The questions of why and are global forest planting slow down at all, are hard to answer. However, errors and uncertainties in statistics do not change our rhetoric for more planted forest. Even if the exact values are uncertain, the remarkable drop in new forest 2005-2015 is too large to rule out uncertainties or factors which has not changed drastically and globally recently as a major cause. We feel certain that more planted forest is a tool for a better world, but conditions vary. Yet, planting forest instead of trusting in nature generally requires better knowledge and competence as well as reasonable stable organization and economy and trust in the politics.
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