John A. Parrotta

Restoration of Degraded Tropical Forest Landscapes

The current scale of deforestation in tropical regions and the large areas of degraded lands now present underscore the urgent need for interventions to restore biodiversity, ecological functioning, and the supply of goods and ecological services previously used by poor rural communities. Traditional timber plantations have supplied some goods but have made only minor contributions to fulfilling most of these other objectives. New approaches to reforestation are now emerging, with potential for both overcoming forest degradation and addressing rural poverty.

Plantation forests and biodiversity: oxymoron or opportunity?

Losses of natural and semi-natural forests, mostly to agriculture, are a significant concern for biodiversity. Against this trend, the area of intensively managed plantation forests increases, and there is much debate about the implications for biodiversity. We provide a comprehensive review of the function of plantation forests as habitat compared with other land cover, examine the effects on biodiversity at the landscape scale, and synthesise context-specific effects of plantation forestry on biodiversity. Natural forests are usually more suitable as habitat for a wider range of native forest species than plantation forests but there is abundant evidence that plantation forests can provide valuable habitat, even for some threatened and endangered species, and may contribute to the conservation of biodiversity by various mechanisms. In landscapes where forest is the natural land cover, plantation forests may represent a low-contrast matrix, and afforestation of agricultural land can assist conservation by providing complementary forest habitat, buffering edge effects, and increasing connectivity. In contrast, conversion of natural forests and afforestation of natural non-forest land is detrimental. However, regional deforestation pressure for agricultural development may render plantation forestry a ‘lesser evil’ if forest managers protect indigenous vegetation remnants. We provide numerous context-specific examples and case studies to assist impact assessments of plantation forestry, and we offer a range of management recommendations. This paper also serves as an introduction and background paper to this special issue on the effects of plantation forests on biodiversity.

Catalyzing native forest regeneration on degraded tropical lands

Abstract Forest clearing, forest degradation through human disturbance, and the deterioration of land productivity due to inappropriate agricultural practices is a major problem in the tropics. Restoration of ecosystem health and productivity has generally relied on abandonment of land and subsequent natural forest succession. In recent years there has been consideration of management options to accelerate recovery and restore productivity, biodiversity and other values. The use of tree plantations to catalyze restoration of degraded forests and lands in the tropics was addressed at a symposium in Washington DC in June 1996. The conclusions and suggestions for future research to develop appropriate management options are reported. There is strong evidence that plantations can facilitate forest succession in their understories through modification of both physical and biological site conditions. Changes in light, temperature and moisture at the soil surface enable germination and growth of seeds transported to the site by wildlife and other vectors from adjacent forest remnants. Development and design of management options to assist this process are required, taking into account socio-economic realities, development priorities and conservation goals.

Development of floristic diversity in 10-year-old restoration forests on a bauxite mined site in Amazonia

Abstract Patterns of plant and animal diversity were studied in a 10-year-old native species reforestation area at a bauxite-mined site at Porto Trombetas in western Para State, Brazil. Understorey and overstorey floristic composition and structure, understorey light conditions, forest floor development and soil properties were evaluated in a total of 38 78.5-m2 plots located in the reforestation area at varying distances up to 640 m from the boundary with the surrounding primary forest. Wildlife surveys focusing primarily on birds and bats were also conducted to assess the role of seed-dispersing animals in regeneration of woody forest species within the plantations and colonization by primary forest species not included in the original reforestation. Regeneration density, species richness and species diversity (Shannon–Wiener index) for woody perennial species, vines, herbs and grasses were strongly correlated with the diversity of planted tree species and structural development parameters, degree of forest floor development and soil pH. The better developed closed-canopy plots (>40% crown closure) were characterized by relatively well-developed litter (O1) and humus (O2) layers, more acidic soils being typical of the surrounding primary forests, and a more diverse herb, vine and woody perennial flora with a greater representation of primary forest species being characteristic of late secondary forests. In closed-canopy plots a total of 125 tree, palm and shrub species were censused (versus 34 in the more open-canopy plots), of which 75 species are known to have been introduced by natural means from the surrounding primary forest (versus 11 species in the open-canopy plots). Among the plantation plots, there was significant colonization by primary forest woody species up to 640 m away from the primary forest edge, although both the abundance and the diversity of colonizing species declined with increasing distance into the plantations. Smaller-seeded primary forest woody species dispersed by mammals and birds represented a higher proportion of the colonizing species compared with the larger-seeded species. These data are consistent with the results of the wildlife surveys, which indicated that most animal seed dispersal is provided by bats, that the most common frugivorous bat and bird species in the plantations feed on small-seeded plant species and that birds and mammals that typically disperse larger-seeded tree species (such as toucans, trogons, tapirs, deer and primates) are still rare in the reforestation area. These results suggest that while the reforestation program has been successful in creating a favorable environment for regeneration of a native primary forest species, further management interventions, such as enrichment plantings, may be required to accelerate regeneration of large-seeded primary forest species.

Restoring tropical forests on lands mined for bauxite: Examples from the Brazilian Amazon

Abstract Restoring self-sustaining tropical forest ecosystems on surface mined sites is a formidable challenge that requires the integration of proven reclamation techniques and reforestation strategies appropriate to specific site conditions, including landscape biodiversity patterns. Restorationists working in most tropical settings are usually hampered by lack of basic information on the wide variety of native tree species that characterize the pre-disturbance forests, as well as insufficient understanding of the ecology of disturbance and natural recovery to design effective restoration programs. A notable exception to this is the forest restoration program developed since the early 1980s by a Brazilian bauxite mining company operating at Trombetas in Para State in central Amazonia. A systematic nursery and field research strategy was used to develop a reforestation program based on mixed plantings of more than 70 native old-growth forest tree species. This technique has been used to replant about 100 ha of deforested minelands each year over the past 15 years. Research in recent years has evaluated this approach and other, generally simpler, reforestation methods used at a smaller scale at this site. Post-plantation biodiversity development and other indicators of restoration success or sustainability were recorded. The results of these studies have shown the overwhelming importance of careful site preparation and topsoil handling/replacement practices in determining both future productivity and biodiversity of the redeveloping forests, irrespective of the complexity of the planting design used. The inclusion of a wide variety of forest species, particularly later successional species, was very important for long-range restoration owing to limitations on natural recovery processes that inhibit seed dispersal and subsequent colonization of many old-growth forest species. Many of the lessons learned at this site are applicable to improve the design of mineland rehabilitation and forest restoration programs worldwide.

Forest Biodiversity and the Delivery of Ecosystem Goods and Services: Translating Science into Policy

Biodiversity is integral to almost all ecosystem processes, with some species playing key functional roles that are essential for maintaining the value of ecosystems to humans. However, many ecosystem services remain nonvalued, and decisionmakers rarely consider biodiversity in policy development, in part because the relationships between biodiversity and the provision of ecosystem services are not generally appreciated. To date, the majority of work in which the functional importance of biodiversity has been examined has been conducted in relatively species-poor systems. Focusing on forest and agroforest systems, we synthesize recent research on the role of biodiversity in the provision of ecosystem services and provide examples of biodiversity science that informs ecosystem management and policy. Finally, we highlight barriers to the transfer of knowledge from scientists to decisionmakers and suggest that scientists can be much more effective at informing policy and improving resource management by asking policy-relevant questions and providing timely and consistent information to decisionmakers and the public on the linkages among biodiversity, ecosystem services, and their value to people.

Secondary forest regeneration on degraded tropical lands

Forest plantations established on degraded sites can accelerate natural succession through their effects on vegetation structure, microclimate, and soils. Spatial and temporal patterns of secondary forest species regeneration were studied in permanent quadrats in Albizia lebbek plantation plots and control areas at a degraded coastal pasture in Puerto Rico. Approximately 6.7 years after plantation establishment, a total of 22 tree and shrub species were found in the plantation plots, compared with only one species (Albizia lebbek) found in the control plots. The majority of tree species in the plantation have seeds that are dispersed by either birds or bats, suggesting that the plantation canopy plays a key role in the regeneration process by providing roosting habitat for seed-dispersing animals. Spatial variations in plantation understory seedling populations were found to be associated with both distance from probable parent trees and understory light intensity. These results indicate profound differences between the plantation and adjacent control plots with respect to their provision of regeneration habitat for secondary forest species, and suggest several factors that should be considered in the design of “foster ecosystems” for the rehabilitation of severely degraded tropical forests.

Biodiversity and ecosystem services: lessons from nature to improve management of planted forests for REDD-plus

Planted forests are increasingly contributing wood products and other ecosystem services at a global scale. These forests will be even more important as carbon markets develop and REDD-plus forest programs (forests used specifically to reduce atmospheric emissions of CO2 through deforestation and forest degradation) become common. Restoring degraded and deforested areas with long-rotation planted forests can be accomplished in a manner that enhances carbon storage and other key ecosystem services. Knowledge from natural systems and understanding the functioning novel of ecosystems can be instructive for planning and restoring future forests. Here we summarize information pertaining to the mechanisms by which biodiversity functions to provide ecosystem services including: production, pest control, pollination, resilience, nutrient cycling, seed dispersal, and water quality and quantity and suggest options to improve planted forest management, especially for REDD-plus.

Traditional forest-related knowledge and sustainable forest management in Asia

Considering the level of degradation of natural resources in Benin and the need of local communities to preserve traditional medicine practices, 41 traditional botanical gardens have been created. Traditional botanical gardens in Benin play many roles but have been designed to reflect society’s priorities, to contribute to well-being, education and research. This form of conservation constitutes a new approach which involves local communities and could contribute to the global conservation of biodiversity in Benin. Many stakeholders are involved in the creation of botanical gardens and this constitutes a great opportunity for the development of this initiative. However, many challenges have to be considered for a sustainable development of traditional botanical gardens in Benin.

Restoration and Management of Degraded Tropical Forest Landscapes

Tropical forest loss and degradation, as well as degradation of lands that formerly supported forest, are proceeding at unprecedented rates, eroding biological diversity and prospects for sustainable economic development of agricultural and forest resources. Between 1980 and 1990, an estimated 15.4 million ha yr−1 of tropical forests and woodlands were destroyed or seriously degraded, principally through agricultural expansion, uncontrolled livestock grazing, logging, and fuelwood collection (Food and Agriculture Organization, 1993). This is equivalent to annual forest cover losses of 0.8%, the greatest losses occurring in moist deciduous forests (6.1 million ha, or 1.00%, y−1) and in tropical rain forests (4.6 million ha, or 0.6%, y−1). Significant losses during this period also occurred in upland forest formations (2.5 million ha, or 1.1%, y−1) as well as in deciduous to very dry forest zones (2.2 million ha, or 0.5%, y−1).