Carbon Changes in Boreal Forests
- Boreal forests, or taiga, form a biome that covers much of North America, Europe, and Russia, and though they have relatively low productivity, these forests are an important carbon sink due to their size
- Boreal forests are at risk of switching from being a carbon sink to being a carbon source due to the effects of global warming on their ecosystem processes
- This switch from sink to source is known as a tipping point
- This further increases the positive feedback effects of global warming
- The reduction in water availability that is caused by global warming is a huge problem for boreal forests
- Less snow falls due to increased temperatures, meaning that less water is available from snow melt water
- This leads to drought, reducing rates of photosynthesis in the coniferous trees of boreal forests
- Reduced photosynthesis means reduced productivity, and over long periods can kill the trees
- Lack of water initially leads to a loss of green pigment and a process called forest browning, where the trees become brown
- Eventually the trees will die
- The dead trees dry out and the risk of forest fires increases
- The loss of boreal forest reduces the removal of carbon dioxide by photosynthesis, and increases the release of carbon dioxide by combustion
- Combustion can release carbon that has been locked up for many years in the living trees, dead needles on the ground, and within the soil itself; this is known as legacy carbon combustion
- This can tip the forests from carbon sink to source, and can be irreversible