At first glance, this question seems absurd. It’s obvious to any English-speaking person that a forest is… well, a forest. A dense collection of trees.
But given this definition, is a forest still a forest if every tree was the same species? If no other type of vegetation was found under the canopy? If the trees were sparsely distributed? Is there a minimum height for “forest” trees?
This ambiguity is the foundation of a debate on how much global forest cover is left. In other words, our inventory of existing forest area changes with how we define a forest.
Our Relationship with “Forests”
Let us consider the origin of the word itself.
The nature of what a forest is to us has actually shifted over time, evolving with our changing relationship to the wilderness. The origin of the word forest is rooted in the Latin word “foris”, a term simply implying “outside” and therefore not privately owned land. In Medieval times, the term took on a legal meaning when disputes over rights to hunting grounds arose. Therefore, a forest could mean scrub or even a wasteland without trees since this was the best type of territory in which to hunt . However, as wild hunting areas were more commonly associated with trees, the word forest became increasingly associated with a wooded, tree-covered area.
But “must contain trees” is not sufficient when it comes to international discussions on how much forest is left on this planet. We must consider what type of forest we are looking for. Under the most basic definition, a patch of land with a concentration of planted palm oil trees would be considered a forest. However, a palm oil plantation is vastly different than a natural forest.
What’s the Difference?
When I did a quick search of studies on the differences between planted forests and natural forests, I found many papers on how planted forests could be sustainable. They outlined, for instance, how replacing a sickly native forest with healthy plantation forests could be more beneficial. While this is true, benefits generally favor natural over planted forests. Differences between the two are generally related to carbon sequestration, biodiversity, and resilience.
As mentioned in a previous post, A Song of Forest and Carbon, forests remove carbon dioxide (CO2) from the atmosphere. The amount of carbon that stays in trees depend on how big they are and how long they remain standing. In natural forests, the majority of carbon resides in the wood of large trees that have been standing for decades, even centuries. Planted forests are generally newer, and individual trees are often removed for commercial use (like timber). These types of forests hold 40% less carbon stock than an unlogged, natural forest . Aside from wood, natural forests take carbon out of the atmosphere through the rich soil the trees grow in. Therefore, soil quality is important to carbon sequestration: degraded quality holds less carbon than good soil. In a 2012 study, deforestation followed by plantation forests left soils in worse quality. The study concluded that the replacement of natural forests by plantations may be a practice best avoided to maintain the ecosystem sustainability .
That biodiversity is greater in natural forests than planted forests isn’t surprising. When was the last time you found a bunch of orangutans thriving within vast rows of oil palms? Generally forests that are diverse and old-growth are home to more species than those forests that are uniform and young. Studies have established that the older, more diverse trees in natural forests support an average of 35% more species than plantations . Losing biodiversity found within natural forests is bad news for us. We depend on plant and animal species differences and richness to help us adapt to changing environments.
While we’re on the topic of changing environments – in the face of climate change, what type of forest is more likely to withstanding temperature changes? A study of forests in Spain – a country experiencing the climate change consequences of both increased annual temperature and decreased precipitation – concluded that natural forests better withstand these changes than planted forests. Natural trees recovered faster after a drought than planted trees, which were less resilient.
So Why is Defining What A Forest Important?
Studies suggest that deforestation rates are decreasing . Good news, right? We are losing less forest cover. But when we look closer, we see that the decreasing rate of forest loss is actually a matter of definition. Loss of natural forests is padded by a great gain in planted forests.
As countries submit their respective plans on how they will mitigate their contributions to climate change, we celebrate when they commit to preserving or increasing forest cover. But we must be careful of what forests mean to each interested party. A commitment to reaching a percentage of forest cover would still technically allow a country to clear natural forests and replace it with timber or pulp and paper trees.
Given attributes of both types of forests, what’s the cost of this exchange?