land use

The second biggest emitting sector in the world is land use. But what is “Land Use”, anyway?

The Intergovernmental Panel on Climate Change defines land use as the total of arrangements, activities, and inputs that people undertake in a certain land cover type, including land under forests, silviculture, shifting cultivation, agroforestry, temporary fallow… What’s that? I can’t hear you over my awesome technical jargon.

Simply put, land use describes how humans change the earth’s surface. It describes the ways in which we take a natural area of land (like forests, and grasslands) and change it for our own use (like cities, and farming).

The Found World

It is strange to think that just 100 years ago, authors like Sir Arthur Conan Doyle were writing about the possibility of finding a Lost World. Now, satellite pictures, even an airplane flight, will show a more organized world. Neat linear lines grid the earth’s surface, outlining corn fields, soy crops, cattle pasture. Human ingenuity is dominating the natural world, so much so that we are now starting to call this epoch the Anthropocene – the age of humans. Our land use has to impact the environment somehow, right?

My background is in environmental impacts of land use. That is, I have studied causes of deforestation and estimated its impacts on climate. Through this work, I have come to find that land use plays a special role in our fight against greenhouse gas (GHG) emissions.

The Thing About Forests

“Save the Rainforest!” campaigns taught us that forests are homes to a variety of animal species. But forests also actively take GHG emissions out of the atmosphere.

Remember this fun graph from high school? Didn't think so.
Remember this fun graph from high school? Didn’t think so.

Science Breakdown: Forests are unique in the way they grow. Forests (along with other plants, algae and bacteria) use energy from sunlight to combine carbon dioxide (CO2) and water (H20) into carbohydrates. Carbohydrates store energy and are used by trees (and humans!) to fuel their living. The output of this process (called photosynthesis), is oxygen – a gas of great importance to humans.

But this isn’t the only benefit of photosynthesis. The absorption of CO2 to make carbohydrates means that forests actively remove GHGs – big time. It is estimated that forests take 10 billion tons of CO2 out of the atmosphere every year. That is roughly equivalent to one quarter of total global emissions. If we removed all earth’s forests, it would mean we would lose that capture, or sequestration, adding that much more CO2 to the atmosphere.

Deforestation Makes Things Worse


So, on top of losing a way to capture CO2, cutting down forests has its own emissions.

When humans change a natural landscape, we are usually cutting down trees for better farmland. This is because the soil that grows our food usually runs out of nutrients.  When this happens, farmers look to more nutrient rich areas to grow more food. Forests indicate a nutrient rich area, it’s why there are so many living thing in it!

However, when we cut down forests, we release GHG emissions. Carbon is held in the wood and leaves of trees. For some communities with no access to heavy machinery, cutting forests down actually means burning them. A burning forest releases carbon in the form of carbon dioxide (CO2), carbon monoxide (CO) and methane (CH4). And after the forest is removed, decomposition of dead branches and brush emits more GHGs into the atmosphere. Every year 5 to 11 billion tons of carbon is emitted into the atmosphere. This is greater than total annual emissions from the European Union.

So, The Lorax Was Right

It’s time to start thinking about ways to reduce forest loss. Forests mean hope for climate change, and countries know this. At talks in Bonn this week, negotiators are working with countries to figure out how to reduce deforestation and/or increase existing forest area. More on the Ins and Outs of these discussions later this week.

Finally, forests offer even more than homes for different species and GHG emissions reductions. They also provide food and other resources for local communities, filter clean water for nearby river systems, and contain plants that have helped cure many diseases. You can find more on how (tropical) forests contribute to health and development here.