Trees produce oxygen as a byproduct of the process known as photosynthesis. During this process, trees take in carbon dioxide from the atmosphere and, with the help of sunlight and chlorophyll, convert it into glucose and oxygen. The oxygen is then released back into the atmosphere, making trees a crucial component in Earth's ecosystem. This oxygen production not only supports human and animal life but also helps in reducing atmospheric carbon dioxide levels, thereby playing a vital role in maintaining environmental balance.