The interactions within natural systems often permit what can be called "elegant solutions" - the satisfaction of multiple needs through a single, often simple action.
One specific application of the elegance principle is the establishment of symbiotic relationships among parties, subsystems and sectors. In natural ecosystems symbiotic relationships evolve in a way which maximizes the efficiency and stability of the overall system.
Ecosystems recycle waste products from one natural process to become the inputs into other processes. This maximizes the use of nutrients and energy in the system and prevents the build-up of waste by-products in the system in the form of "pollutants," which block the exchange of nutrients and energy between organisms.
Trees are an elegant tool for addressing a number of needs in human settlements. While requiring little human investment and energy, trees can simultaneously serve as an amenity for human enjoyment, a source of food and fuelwood, a habitat for various species, an air and water purification tool, a buffer against noise and air pollution, an energy conservation tool to insulate buildings, a soil conservation tool, a sink for atmospheric carbon, and a lever to moderate microclimate. To achieve such a concurrence of benefits, however, urban tree planting must be undertaken in an elegant and strategic way. For instance, trees planted in the middle of the sod-covered, chemical-treated ecological wastelands that we call urban parks do not provide energy conservation, soil conservation, noise pollution control, or, if regularly subjected to lawn chemicals, food supply benefits. Undertaken in an elegant way, urban forestry programs can be an inexpensive and low-maintenance approach to address all of the above needs, as well as many others, such as employment generation, the development of community cohesiveness, and public education.