I am answering under the assumption that those are cacti in the desert. Well as we know, cacti are producers they have the ability to synthesize their own food using photosynthesis which is a process that converts solar energy into glucose “food”. It has the ability to be a good source to small animals with its fruits and seeds. An example is, some insects feed off the nectar from the cacti. A second reason is that cacti are carbon sinks meaning that they take in carbon dioxide. Just to familiarize you the formula for photosynthesis is CO2 + H2O + energy equals glucose + O2 . Without carbon dioxide none of it is possible. Without cacti, CO2 levels would increase leading to bad affects.
