Wealth can be seen as the factories, infrastructure, goods and services the population of a nation dispose of. According to Tim Garrett, a scientist who looks at the economy from the perspective of physics, it is existing wealth that generates economic activity and growth. This growth demands the use of energy as no activity can take place without its use. He also points out that the use of this energy unavoidably leads to concentrations of CO2 in the atmosphere. All this, Tim Garrett says, follows from the second law of thermodynamics. If wealth decreases then so does economic activity and growth. The CLD tries to illustrate how wealth, ironically, now generates the conditions and feedback loops that may cause it to decline. The consequences are inevitably economic stagnation (or secular recession?).
You can read about the connection Tim Garrett makes between 'Wealth, Economic Growth, Energy and CO2 Emissions' simply by Googling 'Tim Garrett and Economy'.