A stable climate is the most fundamental resource of all. No one has yet built a civilisation in an unstable climate.
Good compost is key to thriving garden, it's zero-carbon (possibly even carbon-negative), free, and has positive ecological benefits.
Building up soil organic matter helps retain moisture and improve drainage, improves retention of nutrients, and even makes them more acessible to plant roots. Micro-fauna & flora populations are increased and these provide the basis of a rich food web where invertebrate numbers are boosted which provide meals for birds, hedgehogs and amphibians.