Why is a nutrient cycle on earth called closed system

The nutrient cycle is nature's recycling system. All forms of recycling have feedback loops that use energy in the process of putting material resources back into use. Recycling in ecology is regulated to a large extent during the process of decomposition. Ecosystems employ biodiversity in the food webs that recycle natural materials, such as mineral nutrients, which includes water. Recycling in natural systems is one of the many ecosystem services that sustain and contribute to the well-being of human societies.

HAVE A GOOD DAY!

I have Bolded important facts aswelll

because the light is a great source of energy for the plants to survive. (i hope this )