Planting trees is no solution
The “ecological footprint” is not an article of faith, but an accounting tool that recognizes we currently have only one planet that supports life. The surface of our planet Earth is about 51 billion hectares, but since some is ice, desert and deep ocean, only about one quarter of it is productive (fishing grounds, forests, grazing land, crop land etc.).
With a world population of about 6.7 billion sharing about 13 billion hectares, this gives us roughly 2 hectares per person.
That’s the budget. That’s all we’ve got to go around.
How much biologically productive area does it take to provide all the ecological services we depend on, for food, fiber, waste absorption, city infrastructure, etc?
This is the question that the ecological footprint attempts to answer.
The numbers are, if anything, conservative. They underestimate humanity’s overall demand and human demand can be, and indeed is, larger than what the planet can regenerate. We can cut trees faster than they re-grow and pump carbon dioxide into the atmosphere faster than the biosphere can absorb it.
In his recent commentary, (“More than enough earth,” April 18, page 9) Bjorn Lomborg was correct in describing what the ecological footprint measures. Unfortunately, he misinterpreted what the results of this measurement imply.
For example, he said that the ecological footprint data implies that we must “cut emissions to zero and plant trees to achieve that, meaning we would have to plant forests today on 30 percent more than all of the available land, and plant forests on almost two planets by 2030.”
This is simply wrong.
Ecological footprint accounting lays out the problem and makes it clear when the ecological budget is being exceeded. But there are many possible solutions and as an accounting measure it does not determine which is preferable. What it does make clear, contrary to Lomborg’s claim, is that planting trees is not a viable solution, as there is simply not enough productive area available on Earth for this strategy to succeed.
Lomborg rightly points out that presently, worldwide, about half of the ecological footprint accounts for carbon dioxide. This is how much area it takes to neutralize carbon dioxide emissions. It is the area needed to make sure on Jan. 1 and Dec. 31 we will have the same carbon dioxide concentration in the atmosphere. But we do not have this area available. Therefore, if we want to avoid a continuous increase in carbon dioxide concentration in the atmosphere, emissions need to be cut quite significantly.
Yes, the carbon footprint is the most rapidly growing component of the entire ecological footprint, but most others are growing as well, with the consequence of rapidly shrinking wild animal populations. Footprint data show that if all the people on Earth lived American lifestyles, it would take the regenerative capacity of five planet Earths to provide the needed ecological services.
The Footprint does not speculate about the future, rather it compares actual human demand against actual ecological availability. Any future projections (i.e., by 2030 we will need two planets to support humanity’s demands) are based on data from organizations such as the UN, the Food and Agriculture Organization and the International Energy Agency. This data includes moderate population increase and food, fiber and timber consumption.