This 2 minute video explains it all.
sus·tain·a·bil·i·ty /səˌsteɪnəˈbɪlɪti/ [suh-stey-nuh-bil-i-tee] noun
- the ability to be sustained, supported, upheld, or confirmed.
- Environmental Science . the quality of not being harmful to the environment or depleting natural resources, and thereby supporting long-term ecological balance: The committee is developing sustainability standards for products that use energy.
From the video:
Sustainability means things can keep going. Can sustain themselves. Can continue into the future and go on forever.
From a human perspective, sustainability for our planet means it can continue to do what it was designed to do: provide clean water, clean air, produce safe food and allow us all to have a high quality of life forever.
Unsustainability means it cannot. And that is where we are now.