Final answer:
Ecosystem services are natural processes that provide benefits to humans. Timber and Waste decomposition are examples of ecosystem services, while Erosion is a natural process that can negatively impact these services.
Step-by-step explanation:
Ecosystem services refer to the natural processes and benefits that ecosystems provide, which support human life and well-being. Among the options provided, Timber and Waste decomposition can be described as ecosystem services. Timber is a provisioning service as it provides material for construction and other uses. Waste decomposition is a regulating service, as it breaks down organic material, recycles nutrients, and helps maintain soil health. In contrast, Erosion is not an ecosystem service but rather a natural process that can be influenced negatively by human activities and can degrade ecosystem services by wearing away soil, for example.