Natural Forest Management in the Tropics: Adaptive Management, Applied Ecology, Silviculture

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Society of American Foresters                                                                               International Society of Tropical Foresters


Natural Forest Management in the Tropics: Adaptive Management, Applied Ecology, Silviculture

Francis E. Putz, University of Florida

Managers of natural forests in the tropics need to draw on the expertise of a multitude of disciplines, including the traditional fields of forestry and ecology as well as the equally important disciplines of environmental engineering, geography, sociology, and economics. Whereas there was a time when tropical forests were mostly valued for their timber, modern forest managers are often called upon to manage for timber as well as tourists, to maximize biodiversity and carbon retention, and to strive for a balance between water quality and quantity. The challenges for today’s natural forest managers are considerable given that they are expected to ply their multi-disciplinary trade in a cost-effective manner in the most biologically diverse and least well understood ecosystems in the world.

In this overview of natural forest management in the tropics the following questions are addressed:

1. Management for what?

2. Management for whom?

3. What sort of forest?

4. How to achieve the intended management goals?

Although I will try to avoid placing too much emphasis on commercial timber-producing trees, the focus of decades is hard to change. In my defense, and knowing that I will slip back into my familiar rut, tropical timber is still in great demand and many tropical forests suffer severe and unnecessary degradation when that timber is improperly harvested and otherwise mismanaged.

Management for What? The Multiple Values of Tropical Forests

The goals of tropical forest management are seemingly as diverse as the forests themselves. For example, where forests are to be managed for their amenity value, eco-tourism, or carbon sequestration through avoided deforestation, management mostly involves protection from undesired human interventions (e.g., wildfires, logging, mining, and poaching). Similarly, where wildlife populations are to be maintained or enhanced, management can range from simple protection to provision of water sources, nest cavity excavation, or species reintroduction. Slightly more intensive, management for non-timber forest products generally requires at least close monitoring and control of harvesting, particularly when adult and sub-adults are damaged or killed in the process of extracting the product. Where the principal goal of forest management is to maximize or sustain the yields of timber, a great deal more training, planning, supervision, and monitoring are required given that the impacts are so much more substantial. Finally, it is important to recognize that these different goals of tropical forest management are by no means mutually exclusive. For example, in forests selectively harvested for timber, carbon sequestration can be enhanced by the use of reduced-impact logging techniques (Pinard et al. 2000). Similarly, timber and non-timber forest products can often be profitably and sustainably harvested from the same managed forests (e.g., Romero 1999).

While some forest uses are completely compatible, managers more often have to grapple with tradeoffs among competing uses. For example, even when timber harvesting is very selective and carried out using the best logging practices, it unavoidably decreases standing stocks of forest carbon and increases sediment loads in streams. Similarly, if yields of a commercially valuable species are to be sustained, then silvicultural interventions are often needed to enhance their rates of reproduction, growth, and survival (Fredericksen and Putz 2003). Managing for some species necessarily means managing against others, hence the tradeoffs about which natural forest managers need to be informed.

The rallying cry for natural resource management in general and tropical forest management in particular is “sustainability.” While this goal is admirable, natural forest managers need to be clear about what exactly it is that they are supposed to sustain (e.g., Gale 1991, 1994). Traditionally the goal was sustaining timber yields, but it was seldom made clear whether sustainability could be claimed if harvested volumes were maintained by changing species at each forest entry with attendant reductions in standing stocks. Alternately, jobs or lifestyles might be sustained or the focus might be more on water flows, biodiversity, or carbon stocks. More fundamentally, some scholars question whether, in the name of sustainability, it is acceptable to exchange natural capital (e.g., timber stocks) for social capital (e.g., well-being), which might allow utility-maximizing decisions that involve over-harvesting or even forest conversion to some more lucrative land use (Luckert and Williamson 2005) . Whether society wishes to accept such tradeoffs of natural for social capital is a normative decision that should not be made by natural forest managers alone, but the answer to this question will greatly influence what the managers can do and where (McCool and Stankey 2004).

Management for Whom? The Clients of Tropical Forest Managers

Up until recently and to this day in some places, the phrase “natural forest management” is taken to mean manipulations of stands of trees for production of commercial timber. The “clients” for these management efforts were traditionally forest industries and the governmental forest agencies they supported. Nowadays, with the much broader set of answers to the question of “management for what?” has come a much more diverse set of clients or stakeholders. Forest industries are still important players in many places and much tropical forest is still “owned” by central governments, but managers now answer to private forest owners, community forest owners, and intermediaries all along the forest product marketing chain including certification bodies.

Many tropical forests are still managed for timber by employees of large industrial concessions granted to wealthy individuals or large firms (Dawkins and Philip 1998). Although this approach failed in many formerly forest-rich places in the tropics (e.g., Malaysia; Jomo et al. 2004), Brazil is implementing a concession-based system in a huge portion of its Amazonian forest (Veríssimo et al. 2002). In most industrial concessions, unless there are strong incentives or well-enforced regulations, natural forest management generally consists of implementing restrictions on where and what timber harvesting is permitted. Typically, annual cutting areas are allocated on the basis of assumed and woefully inflated rates of timber volume increments, often based on total, not merchantable timber growth volumes (e.g., 1-5 m3/ha/year), and a limit on the minimum diameter tree that can be harvested (e.g., 45-55 cm dbh; diameter at 1.4 m above the ground; e.g., Dauber et al. 2005). Even the most basic improvements in forest harvesting practices such as training workers in directional tree felling to avoid damaging future crop trees, to facilitate log yarding, and to reduce the extremely high rates of injury and fatalities in the tropical forest logging industry are seldom implemented (Putz et al. 2000).

Recognizing that they failed in their efforts to manage sustainably the forests in their charge and in response to growing public pressure for reform, central governments have “devolved” control over vast areas of tropical forests to local communities. It is estimated that more than 25% of the world’s tropical forests are now in the control of indigenous groups and other rural groups (White and Martin 2002). As clients for the services of natural forest managers, community groups require a different approach than is used when the needs of industrial forest firms are being served. Often rural institutions are poorly developed, which means that the simple provision of forest management plans is only the first step towards wise forest use. On the positive side, compared to their industrial counterparts, local land owners are often more willing to consider the long-term implications of forest management decisions, they generally have lower expectations for quick profits, and they generally view forests as a source of more than just commercial timber (Putz 2000).

Understanding the needs, goals, and perspective of their client is critical for natural forest managers because it is generally the client who decides how to balance the costs and benefits of different interventions. For example, the client might be willing to forego windfall profits so as to assure a steady long-term income or vice versa. Unfortunately often, clients do not fully understand the relevant tradeoffs (e.g., understory bird diversity vs. forest fragmentation by road opening), which means that forest managers end up playing the roles of extension foresters, environmental educators, and business managers. Where independent third-party auditors from certification bodies like the Forest Stewardship Council are involved in the forest management decision-making process, other limitations and opportunities are often introduced (Dickinson et al. 2004, Cubbage 2007).

What Sort of Forest is to be Managed?

No two tropical forests are exactly the same and thus management prescriptions need to be tailored to local biophysical, social, political, and economic conditions as well as the desires of the client. For example, wood yields for charcoal production have been demonstrated to be sustainable by clearcutting small patches in mangrove forests in Malaysia, but the same approach to harvesting would only result in vine tangles or bamboo dominance in Amazonian Bolivia. Even within Malaysian mangrove forests there are areas, like those with many Acrostichum ferns in the understory, where even small clearcuts are best avoided. These examples, it should be noted, address only the ecological aspects of harvesting without mention of the socioeconomic and other conditions that often determine what approach to management is most appropriate.

If we continue to consider only the ecological factors that influence management decisions, there are some fundamental features of natural forests that need to be considered. For example, in every forest there are biophysical limitations and opportunities that managers need to keep in mind. Aspects such as elevation, slope, drainage, soil trafficability, and risks of fires and weed infestations are all basic characteristics of forests that deserve attention. Depending on the client being served, if a forest is of particularly high biodiversity or conservation value, then this status needs to be addressed when management decisions are made. Alternatively, a forest that is still recovering from a severe natural or anthropogenic disturbance might be more suitable for and amenable to more drastic management interventions.

Landscape context should have a big influence on forest management decisions. For example, on financial grounds, intensive management cannot usually be justified in forests that are remote or otherwise of difficult access. In contrast, for accessible forests growing on fertile soils, the “opportunity costs” of maintaining forest cover are often so high as to preclude any but the most intensive forest uses, unless forest conversion is disallowed or financial incentives are provided for maintaining forest cover (e.g., payments for ecosystem services such as carbon sequestration; Chomitz 2007).

Tools and Techniques for Natural Forest Management

The tropical forest manager’s portfolio of techniques and tools should be as diverse as the forests in which they ply their trade. Where timber production is the primary goal, silviculturalists have a wide range of approaches that can be tailored to most conditions in the tropics (for an introduction see Wadsworth 1997, Oliver and Galloway 2007). Non-timber forest product managers can use many of the same tools as timber stand managers (e.g., treatments to promote regeneration, growth, and survival such as soil scarification and liberating future crop plants from competition), tailored to their particular species, forest, and production system. Where assuring water quality and quantity are among the principal objectives of forest management, the multitude of tools and techniques of hydrologists should be employed (e.g., Brooks 2007, Ice 2007). Similarly, other fields such as wildlife biology and ecotourism all have their own approaches to management and their respective tools for use by natural forest managers .

Natural forest management is basically applied forest ecology. Using a life cycle approach, managers first need to assure that the density of reproductive individuals is sufficient to secure the regeneration needed for future crops. There are no hard-and-fast rules about minimum population densities, but when populations are drawn down too low by harvesting the best individuals, the dysgenic effects of this sort of selection is of concern. If there are sufficient parents, the next question is whether conditions are suitable for establishment of juveniles or vegetative regeneration by coppicing (Galloway 2007). Once established, growth and survival of future crop individuals can be enhanced by liberating them from competition of near neighbors (e.g., Wadsworth and Zweede 2006). Finally, when the crop individuals are mature, harvesting should be guided so as to be an integral component of forest management not simply a destructive mining operation in which natural resources that are renewable are not treated as such.


The discipline of natural forest management in the tropics is in jeopardy partially due to lack of adequately trained practitioners. This shortage of expertise is probably related t the fact that simply being able to recognize the hundreds of species involved in tropical forest management requires a great deal of time in the forest, often under difficult conditions and with only modest rewards. In contrast, the fiber farms that draw away many foresters are typically accessible by road, can be extraordinarily productive and profitable, and are amenable to biotechnological innovations such as genetic engineering.

The other reason why many natural forest managers are being left by the wayside is that they are unwilling to accept the fact that society views forests a more than just a source of commercial timber. Too many have failed to recognize or react to the fact that many people, including many important decision-makers, have lost trust in the “timber beasts” of yore.

Tropical forest management reform has allowed ecologists to take the lead in managing for carbon and biodiversity, encouraged social scientists to learn enough about forest management to work effectively with rural communities in their now extensive forests, and has given credence to the claims of economists and environmentalists that because forest management is not particularly lucrative but causes severe environmental damage, the tropical forests that remain should not be managed at all (Rice et al. 1997; but see Putz 2004). If tropical forest managers are going to play their deservedly leading role in forest management, they will need to adopt these expanded views of tropical forests, and manage tropical forests to produce a wider array of commodity goods and environmental services for local communities, their countries, and the world.


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Posted 16 August 2007

Updated 23 August 2007

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