Gert-Jan Nabuurs

Forest carbon sinks in the northern hemisphere

There is general agreement that terrestrial systems in the Northern Hemisphere provide a significant sink for atmospheric CO2; however, estimates of the magnitude and distribution of this sink vary greatly. National forest inventories provide strong, measurement-based constraints on the magnitude of net forest carbon uptake. We brought together forest sector C budgets for Canada, the United States, Europe, Russia, and China that were derived from forest inventory information, allometric relationships, and supplementary data sets and models. Together, these suggest that northern forests and woodlands provided a total sink for 0.6–0.7 Pg of C per year (1 Pg = 1015 g) during the early 1990s, consisting of 0.21 Pg C/yr in living biomass, 0.08 Pg C/yr in forest products, 0.15 Pg C/yr in dead wood, and 0.13 Pg C/yr in the forest floor and soil organic matter. Estimates of changes in soil C pools have improved but remain the least certain terms of the budgets. Over 80% of the estimated sink occurred in one-third of the forest area, in temperate regions affected by fire suppression, agricultural abandonment, and plantation forestry. Growth in boreal regions was offset by fire and other disturbances that vary considerably from year to year. Comparison with atmospheric inversions suggests significant land C sinks may occur outside the forest sector.

Adaptive forest management in central Europe: Climate change impacts, strategies and integrative concept

Abstract Climatic warming may lead to increased or decreased future forest productivity. However, more frequent heat waves, droughts and storms and accompanying pathogen attacks are also expected for Europe and are considered to be increasingly important abiotic and biotic stress factors for forests. Adaptive forestry can help forest ecosystems to adapt to these new conditions in order to achieve management goals, maintain desired forest ecosystem services and reduce the risks of forest degradation. With a focus on central Europe, this paper presents the following management strategies: (1) conservation of forest structures, (2) active adaptation, and (3) passive adaptation. The feasibility and criteria for application of the different strategies are discussed. Forest adaptation may entail the establishment of “neonative” forests, including the use and intermixing of native and non-native tree species as well as non-local tree provenances that may adapt better to future climate conditions. An integrative adaptive management concept is proposed that combines (1) species suitability tests and modelling activities at the international scale, (2) priority mapping of adaptation strategies at the national to regional scale, and (3) implementation at the local scale. To achieve this, an international experimental trial system is required to test suitable adaptive measures throughout Europe and worldwide.

Positive biodiversity-productivity relationship predominant in global forests.

Global biodiversity and productivity The relationship between biodiversity and ecosystem productivity has been explored in detail in herbaceous vegetation, but patterns in forests are far less well understood. Liang et al. have amassed a global forest data set from >770,000 sample plots in 44 countries. A positive and consistent relationship can be discerned between tree diversity and ecosystem productivity at landscape, country, and ecoregion scales. On average, a 10% loss in biodiversity leads to a 3% loss in productivity. This means that the economic value of maintaining biodiversity for the sake of global forest productivity is more than fivefold greater than global conservation costs. Science, this issue p. 196 Global forest inventory records suggest that biodiversity loss would result in a decline in forest productivity worldwide. INTRODUCTION The biodiversity-productivity relationship (BPR; the effect of biodiversity on ecosystem productivity) is foundational to our understanding of the global extinction crisis and its impacts on the functioning of natural ecosystems. The BPR has been a prominent research topic within ecology in recent decades, but it is only recently that we have begun to develop a global perspective. RATIONALE Forests are the most important global repositories of terrestrial biodiversity, but deforestation, forest degradation, climate change, and other factors are threatening approximately one half of tree species worldwide. Although there have been substantial efforts to strengthen the preservation and sustainable use of forest biodiversity throughout the globe, the consequences of this diversity loss pose a major uncertainty for ongoing international forest management and conservation efforts. The forest BPR represents a critical missing link for accurate valuation of global biodiversity and successful integration of biological conservation and socioeconomic development. Until now, there have been limited tree-based diversity experiments, and the forest BPR has only been explored within regional-scale observational studies. Thus, the strength and spatial variability of this relationship remains unexplored at a global scale. RESULTS We explored the effect of tree species richness on tree volume productivity at the global scale using repeated forest inventories from 777,126 permanent sample plots in 44 countries containing more than 30 million trees from 8737 species spanning most of the global terrestrial biomes. Our findings reveal a consistent positive concave-down effect of biodiversity on forest productivity across the world, showing that a continued biodiversity loss would result in an accelerating decline in forest productivity worldwide. The BPR shows considerable geospatial variation across the world. The same percentage of biodiversity loss would lead to a greater relative (that is, percentage) productivity decline in the boreal forests of North America, Northeastern Europe, Central Siberia, East Asia, and scattered regions of South-central Africa and South-central Asia. In the Amazon, West and Southeastern Africa, Southern China, Myanmar, Nepal, and the Malay Archipelago, however, the same percentage of biodiversity loss would lead to greater absolute productivity decline. CONCLUSION Our findings highlight the negative effect of biodiversity loss on forest productivity and the potential benefits from the transition of monocultures to mixed-species stands in forestry practices. The BPR we discover across forest ecosystems worldwide corresponds well with recent theoretical advances, as well as with experimental and observational studies on forest and nonforest ecosystems. On the basis of this relationship, the ongoing species loss in forest ecosystems worldwide could substantially reduce forest productivity and thereby forest carbon absorption rate to compromise the global forest carbon sink. We further estimate that the economic value of biodiversity in maintaining commercial forest productivity alone is

Mapping tree density at a global scale

166 billion to

Ecologically implausible carbon response

490 billion per year. Although representing only a small percentage of the total value of biodiversity, this value is two to six times as much as it would cost to effectively implement conservation globally. These results highlight the necessity to reassess biodiversity valuation and the potential benefits of integrating and promoting biological conservation in forest resource management and forestry practices worldwide. Global effect of tree species diversity on forest productivity. Ground-sourced data from 777,126 global forest biodiversity permanent sample plots (dark blue dots, left), which cover a substantial portion of the global forest extent (white), reveal a consistent positive and concave-down biodiversity-productivity relationship across forests worldwide (red line with pink bands representing 95% confidence interval, right). The biodiversity-productivity relationship (BPR) is foundational to our understanding of the global extinction crisis and its impacts on ecosystem functioning. Understanding BPR is critical for the accurate valuation and effective conservation of biodiversity. Using ground-sourced data from 777,126 permanent plots, spanning 44 countries and most terrestrial biomes, we reveal a globally consistent positive concave-down BPR, showing that continued biodiversity loss would result in an accelerating decline in forest productivity worldwide. The value of biodiversity in maintaining commercial forest productivity alone—US

Trees as carbon sinks and sources in the European Union

166 billion to 490 billion per year according to our estimation—is more than twice what it would cost to implement effective global conservation. This highlights the need for a worldwide reassessment of biodiversity values, forest management strategies, and conservation priorities.

Sustainable management regimes for Europe's forests - a projection with EFISCEN until 2050

The global extent and distribution of forest trees is central to our understanding of the terrestrial biosphere. We provide the first spatially continuous map of forest tree density at a global scale. This map reveals that the global number of trees is approximately 3.04 trillion, an order of magnitude higher than the previous estimate. Of these trees, approximately 1.30 trillion exist in tropical and subtropical forests, with 0.74 trillion in boreal regions and 0.66 trillion in temperate regions. Biome-level trends in tree density demonstrate the importance of climate and topography in controlling local tree densities at finer scales, as well as the overwhelming effect of humans across most of the world. Based on our projected tree densities, we estimate that over 15 billion trees are cut down each year, and the global number of trees has fallen by approximately 46% since the start of human civilization.

A forest management map of European forests

Arising from: F. Magnani et al. 447, 849–851 (2007)10.1038/nature05847; Magnani et al. replyMagnani et al. present a very strong correlation between mean lifetime net ecosystem production (NEP, defined as the net rate of carbon (C) accumulation in ecosystems) and wet nitrogen (N) deposition. For their data in the range 4.9–9.8 kg N ha-1 yr-1, on which the correlation largely depends, the response is approximately 725 kg C per kg N in wet deposition. According to the authors, the maximum N wet deposition level of 9.8 kg N ha-1 yr-1 is equivalent to a total deposition of 15 kg N ha-1 yr-1, implying a net sequestration near 470 kg C per kg N of total deposition. We question the ecological plausibility of the relationship and show, from a multi-factor analysis of European forest measurements, how interactions with site productivity and environment imply a much smaller NEP response to N deposition.

Article 3.3 and 3.4 of the Kyoto Protocol: consequences for industrialised countries’ commitment, the monitoring needs, and possible side effects

The carbon (C) sinks and sources of trees that may be accounted for under Article 3.3 of the Kyoto Protocol during the first commitment period from 2008 to 2012 were estimated for the countries of the European Union (EU) based on existing forest inventory data. Two sets of definitions for the accounted activities, aAorestation, reforestation and deforestation, were applied. Applying the definitions by the Food and Agricultural Organization of the United Nations (FAO), the trees were estimated to be a C source in eight and a C sink in seven countries, and in the whole EU a C source of 5.4 Tg year ˇ1 . Applying the definitions by the Intergovernmental Panel of Climate Change (IPCC), the trees were estimated to be a C source in three and a C sink in 12 countries, and in the whole EU a C sink of 0.1 Tg year ˇ1 . These estimates are small compared with the C sink of trees in all EU forests, 63 Tg year ˇ1 , the anthropogenic CO2 emissions of the EU, 880 Tg C year ˇ1 , and the reduction target of the CO2 emissions, 8%. In individual countries, the estimated C sink of the trees accounted for under Article 3.3 was at largest 8% and the C source 12% compared with the CO2 emissions. 7 2000 Elsevier Science Ltd. All rights reserved.

Patterns of covariance between airborne laser scanning metrics and Lorenz curve descriptors of tree size inequality

Abstract In Europe, forest policy discussions are moving towards a European Union-wide strategy. This will further intensify the relations between European countries in the field of forests and forest management. European-wide forest planning and decision-making require that policy makers have insight into the long-term development of European forests under alternative regimes. The European Forest Information Scenario Model (EFISCEN) was used to make projections of the development of the European forests under four scenarios: (1) business as usual; (2) EFISCEN European timber trend studies (ETTS); (3) maximum sustainable production; and (4) multifunctional management. The simulations were carried out for 30 countries individually, i.e. harmonized scenarios were run, but the special circumstances and demands that play a role in each country were taken into account. The simulations covered 139.2 million ha increasing to 143 million ha in 2050. The initial year varied per country, but was mostly in the region of 1990. The average age of European forests was 57 years in 1990 with a mean growing stock of 142 m 3 ha −1 . The results showed that the future European total fellings may vary between a stable amount of 400 million m 3 year −1 in the ‘business as usual’ scenario to 647 million m 3 year −1 in the ‘maximum sustainable production’ scenario. The other two scenarios incorporated a 9% gradual increase in fellings over the first 30 years of the simulation period (i.e. 0.3% year −1 ). The average growing stock will rise to approximately 250 m 3 ha −1 in 2050, with the exception being the ‘maximum sustainable production’ scenario, in which the growing remains at approximately 137 m 3 ha −1 . The average net annual increment remains at approximately 5 m 3 ha −1 year −1 throughout the simulation period, almost irrespective of the scenario. In the multifunctional scenario, special attention was paid to nature values by increasing the area of strict reserves from 4 million ha in 1990 to 12.3 million ha in 2050 (8.6% of the total forest area). The assumed increase in fellings of 0.3% year −1 appeared possible in combination with this area of reserves. The simulations showed that growing stock development and increment development differed very much for each country separately per scenario. Therefore, the results show a strong need for maintaining the national diversity that constitutes European forestry within harmonized European-wide forest management strategies. In this article, we address what the consequences of each scenario are for wood production, biodiversity, and environmental functions of the forest. The results provide policy makers with a challenge on whether to intervene in the ongoing trend of build-up of growing stock and whether to choose for biodiversity, for increased use of domestically produced wood products, or a combination of these, but spatially separated.