Forests Have an Important Role in Climate Solutions
Carbon Sequestration and a Changing Climate
Forests Have an Important Role in Climate Solutions
To understand how forests fit in to the whole issue of climate change we have to step back and look at the global picture. The details may be complicated but the basic story is easy to comprehend.
The big picture
Our earth is blanketed by a relatively thin atmosphere that contains a number of gases that are vital and necessary to our well-being. Many of these gases trap heat from the sun, creating a greenhouse effect that keeps the earth at a livable temperature. Too much of these insulating gases, however, can trap excess heat, resulting in changes to the earth’s temperature.
There is not much leeway. Even a very small change in average temperature can cause far-reaching disruptions in the life cycles of plants and animals.
Carbon, in the form of carbon dioxide (CO2), is one of the major greenhouse gases and the main culprit in global climate change.
Follow the carbon
To understand the problem and its possible solutions we have to follow the carbon. Looking at the world through a carbon lens provides an entirely new perspective on forests.
Carbon moves through the land, atmosphere, and ocean in a complex cycle.
Trees and other plants withdraw carbon dioxide from the atmosphere through photosynthesis and turn it into biomass—trunks, leaves, roots, etc. Animals eat the plants and thereby incorporate carbon into their bodies.
When plants or animals die, or leaves fall, the process is reversed. The biomass decomposes, and the carbon turns into CO2 and goes back into the atmosphere.
To make this just a bit more complicated, trees, along with all living things, also release CO2 through respiration. In order to figure out how much carbon is actually stored in trees we have to look at the net balance between how much carbon is taken in and how much respired.
Young vs. old
Young, fast-growing trees have a rapid rate of carbon sequestration (uptake and storage of carbon from the atmosphere). They take up more carbon than they lose through respiration, resulting in increased biomass. This rate slows as trees age. Mature forests may become carbon neutral, balanced between sequestration and respiration. However, mature forest ecosystems already contain a huge amount of carbon stored in biomass and soil.
Carbon from the past
There have been periods in the past when photosynthesis exceeded respiration and organic material built up forming coal, oil, and natural gas over millions of years—the “fossil fuels.” When these fuels are extracted and burned for energy this previously stored carbon is released. This is the carbon that is largely responsible for the current increase in greenhouse gases driving global climate change.
Where do forests fit in?
Forest carbon is found in five major areas (called pools): above-ground biomass, below-ground biomass, litter, dead wood, and organic carbon in the soil. The way we manage forests affects the dynamics of each pool.
Forests can take carbon out of the atmosphere, thereby countering some fossil fuel emissions.
This can be done at a low cost and we have the tools necessary—the technology for growing and managing trees is well known.
There are two main parts to the greenhouse gas equation: 1) the release of gases (mostly carbon) into the atmosphere, and 2) the removal of those gases. Most attention to date has been directed toward the first part through efforts to reduce the amount of CO2 released from fossil fuels. The focus on forests is an attempt to increase the second part of the equation: carbon removal and storage.
Forests play a dual role. They are a carbon sink (take up carbon) through photosynthesis but become an emission source (release carbon) when forests are lost and the land converted to other uses. Along with growing healthy forests it is vital to prevent forest loss. Worldwide, about 20% of today’s human-caused global CO2 emissions have been attributed to forest loss.
Fire is an important part of the carbon cycle. Fire consumes organic matter, releasing greenhouse gases including CO2, methane, carbon monoxide, and other materials. Trees and plants not immediately consumed in the fire may be killed and decompose rapidly, releasing CO2.
Although fire produces carbon emissions, it is also a natural and necessary part of the ecosystem, especially in California where plants are adapted to fire. Rather than eliminate fire, the goal is to maintain historical fire regimes and thus avoid catastrophic fires that occur when fuels build up to unnatural levels.
Biomass to energy
In a win-win for both the forest and the atmosphere, thinnings from overstocked forests can be burned to produce energy. Generating electricity in a biomass plant reduces our demand for fossil fuels while at the same time reducing wildfire hazard. The rising price of electricity is rapidly reaching the point where biomass is more financially feasible, and utilities are looking to biomass as an important part of their renewable energy portfolio. Concern for national energy security is also driving research on cost-effective means to convert wood to ethanol.
Wood products are another major carbon pool. A pound of wood contains about a half pound of carbon. Products made out of wood can retain their carbon stores for varying lengths of time, until they decompose or burn. Some products, such as homes, may last for a hundred years while other wood products retain their carbon for much shorter periods.
Expanding the use of wood products is a climate-friendly strategy since steel, plastic, aluminum, and concrete require much more energy to manufacture and produce much higher greenhouse gas emissions.
Should we care?
The earth as a whole is warming. But the term global warming isn’t quite accurate. Not all areas will get warmer. Some will be colder, some will be wetter or drier, there may be more storms, or more intense weather events. While no one knows exactly what will occur where, climate change is now well-acknowledged as a threat to our economy, environment, and health.
In California, predicted effects include reduction in the Sierra snowpack, reduced water quantity and quality, sea level rise, coastal erosion, increases in infectious diseases and other health problems, and changes in natural ecosystems including forests.
How can we increase carbon sequestration in forests?
The management practices used to increase forest carbon sequestration are the same ones that promote good forest health. The goal is to encourage trees to grow and thrive, to get bigger faster, and to reduce the risk of wildfire.
There are three main strategies for forest mitigation of climate change:
1. Conserve existing forests in a healthy condition through proper management,
2. Increase carbon sequestration by planting trees or other forest management techniques that increase biomass,
3. Increase the use of wood products and substitute wood for materials that require energy-intensive production.
A good way to keep up on current events is through the California Climate Portal
Governor’s Climate Action Team reports
International guidelines for conducting national greenhouse gas inventories by the International Panel on Climate Change (IPCC). The portion on “Agriculture, Forestry and Other Land Uses” (AFOLU) lays out forest methods and accounting procedures.
The Center for Clean Air Policy evaluates carbon gains from a broad range of alternative forest and agricultural policies in California with a useful bibliography.