Conventional money is supposed to be doing everything. By adding in complementary currencies, you actually get different types of things and different outcomes from different complementary currencies.

Basically, for any complex to be sustainable needs to have a balance between two factors: resilience and efficiency. These two factors can be calculated from the structure of the network that is involved in a complex system. A resilient, efficient system needs to be diverse and interconnected. On the other hand, diversity and interconnectivity decrease efficiency. Therefore, the key is an appropriate balance between efficiency and resilience.

The direct consequence is that we have to fight with each other in order to survive.

When the banks create the money, they don't create the interest. They send you into the world to compete with everybody else to get the second $100,000 that never was created and bring it back to them. So if we're in a world with zero-growth population, goods, services, and money, the problem would be obvious.

The Future of Money: Creating New Wealth, Work, and a Wiser World

Complementary currencies work in addition to existing money, rather than replacing existing, official money. There are whole different families of complementary currencies. One of them is local currencies. One is regional currencies. Another is functional currencies. Another is social-purpose currencies.

Conventional money is supposed to be doing everything. By adding in complementary currencies, you actually get different types of things and different outcomes from different complementary currencies.