Forest definitions vary widely

There are at least 1,000 different definitions of the word "forest," and the way it is defined has significant consequences for understanding issues related to the economy, ecology, and climate.

Ecologists challenge simple definitions

For an ecologist, a plantation of trees that are all the same species and size cannot be considered a forest. This distinction matters because it affects how areas are protected and supported through environmental policies.

Forests as complex ecosystems

From an ecological standpoint, a forest is an ecosystem with a tree layer that supports a high degree of biodiversity. About 80% of the world's terrestrial biodiversity lives in forests, where living and non-living elements interact in complex ways.

Interdependence in forests

In forests, relationships between organisms are crucial. For example, jays that disperse acorns help oak forests regenerate, and mycorrhizal fungi assist trees in absorbing water and minerals from the soil.

Decomposition and recycling in forests

Saproxylic fungi and beetles play a vital role in breaking down dead wood on the ground, which helps recycle organic matter and improve soil fertility. These processes are especially important in forest ecosystems.

Forest structure and complexity

Forests have a unique structure due to the presence of trees, leading to varied distributions of light, shade, humidity, and heat. This creates a habitat for a wide range of plants, such as the lily-of-the-valley (Scilla lilio-hyacinthus), which thrives in oak forests.

Monoculture plantations lack diversity

Botanist Francis Hallé warns that tree plantations, especially those with a single species, reduce biodiversity and simplify the structure of ecosystems. These plantations are less resilient and cannot provide the same ecological benefits as natural forests.

Hybrid approaches to forest management

In some cases, intermediate forms of forest management can be found. For example, in the "forest" of the Landes, introducing species diversity into pine plantations can gradually transform them into more natural forest ecosystems.

Official forest definitions are simplistic

Administrative definitions, such as those from the National Forest Inventory or the Food and Agriculture Organization of the United Nations (FAO), define a forest as a land with at least 10% tree cover and an area larger than 0.5 hectares. These definitions can include many types of arboreal vegetation.

Forest diversity across the globe

Forests vary greatly around the world, differing in structure, biodiversity, history, dynamics, and function. Some have a single layer of trees, like mangroves, while others have multiple layers and a wide range of tree species.

Temporal and age-related differences

The structure of forests can change over time, influenced by the seasons and the life cycles of the species present. Some forests have even-aged trees, while others have a mix of different-aged trees.

Biodiversity varies by region

Tropical forests can contain up to 600 tree species per hectare, while temperate forests may have only about fifteen. Some forests are dominated by a single species, such as those in mountainous regions where only one type of tree can survive.

Human influence on forest development

Forests are shaped by their history, age, and human activities. In Europe, there are no primary forests left, but subnatural forests—those that are mature and have high naturalness—come closest to them. These forests are important for carbon storage and fire prevention.