Sustainability is important for development because in the absence of sustainability, the development that comes forth will be short lived and will not serve much purpose in the long run.
It is therefore very important that whether it is with regards to the use of resources or the general impact on the environment, developmental goals should also be accompanied with sustainability. If we rampantly use the resources for development, such a development will cease to exist once such resources are exhausted. Hence, we should always think about sustainability and development in tandem.