Final answer:
Tax incentives are one mechanism used by states to encourage regional planning that results in environmental protection.
Step-by-step explanation:
One mechanism used by states to encourage regional planning that results in environmental protection is tax incentives. Tax incentives are used to provide financial benefits to individuals or companies who engage in activities that promote environmental protection, such as investing in renewable energy or implementing sustainable practices. These incentives serve as a way to encourage and reward environmentally responsible behavior.