Respiration of plants and trees is more important. Plants are also taking carbon out of the atmosphere through photosynthesis. Animals are not large sources of CO 2 . Animals are more important for methane emissions. The increase in forest burning is one cause of the increase in carbon dioxide.
Land clearing is also a significant, related source.
Over the last 20 years, the contribution of burning and clearing to the atmosphere has been approximately balanced by the remaining biosphere taking out carbon dioxide through photosynthesis. This may be because the biosphere has been stimulated by greater atmospheric CO 2 levels, for example. We may run out of fossil fuels but we re talking about a very long time. There are very large amounts of fossil fuel reserves out there. If we burnt all of them, depending on the rate, this would lead to an enormous increase in atmospheric carbon dioxide.