Guiding Principles

Forest Definitions Influence Approaches and Outcomes of Reforestation

Chazdon, R. L., P. H. Brancalion, L. Laestadius, A. Bennett-Curry, K. Buckingham, C. Kumar, J. Moll-Rocek, I. C. G. Vieira, and S. J. Wilson. 2016. When is a forest a forest? Forest concepts and definitions in the era of forest and landscape restoration. Ambio 45: 538-550.


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Flying in an airplane across Sabah, Malaysia, one can see abrupt change from natural forest fragments in montane regions to huge expanses of oil palm in lowland areas. Although these two types of tree cover differ greatly in their natural features and values for people, both types of vegetation are technically defined as forest by many international agencies and land-use scientists alike. If a patch of native rainforest is cleared and replaced with a eucalyptus, rubber, or oil palm plantation, the same definition of forest applies, despite dramatic changes in ecosystem services and socio-economic outcomes. In some cases, broad definitions of forest may lead to the misleading conclusion that deforestation never happened, as tree cover persisted over time.

The classification of monoculture plantations as ‘forest’ exemplifies how the definition of ‘forest cover’ is highly variable and depends on values associated with what the forest provides to people and nature. A forest may be seen as a source of timber, an ecosystem containing important biological diversity, a home for indigenous people, or a sink for carbon. A single, uniform definition of forests is unable to capture these diverse perspectives, and applying only one definition can hinder conservation, management, and restoration efforts. Yet, clear definition criteria are needed for assessing forest loss or gain at large spatial scales, as well the multiple impacts of converting one “type” of forest to another.

To address this predicament, our international research team documented historical forest definitions and concepts to provide guidelines for researchers and policy makers to navigate the complex landscapes of modern forests and tree plantations. The most widely used forest definitions today are based on minimum values of land area, tree height, and canopy cover. While useful for general assessment of forests, these broad definitions fail to account for the nuances in social and ecological forest properties, including their origins and future trajectories. Standardized assessments of total forest cover overlook important features, such as carbon storage, the proportion of native species, or species used by local people.

The way forward requires multiple definitions designed and applied to specific goals. Definitions that distinguish old-growth forests from recently replanted or regenerated forests and continuous forests from fragmented forests are important to make sound conservation and restoration decisions that affect human and non-human lives. Developing and applying definitions that incorporate forest dynamics and distinguish between types and trajectories of tree cover will allow us to recognize, assess, and value the various benefits of all forest types, now and in the future.


The PARTNERS connection
This paper originated at the first PARTNERS workshop in 2014, where it became apparent that ecologists and Forest Transition theorists had vastly different ways of using the word ‘forest.’ We decided that a discussion of ‘what is a forest’ was needed to further an interdisciplinary research agenda focused on the ecological properties of different types of returning forests, and their value to people.  The paper has since been highly cited by a range of academic publications and web media, and academics and practitioners. The journal also selected it to be summarized as a short video because of the importance of this paper to society.