Complex living systems (such as you, me, ecosystems, and even social organizations such as companies) maintain their state of ‘aliveness’ by using complex feedback systems.
Here is an example of a feedback system. In order to survive our body temperature cannot vary far from 37 °C. If we are exposed to excessive heat, our nervous systems sense the temperature changes in our bodies, and send signals (information) to our brains. The brain responds by ordering different parts of the body to react by sweating, panting, increasing blood supply to the skin surface, and moving to a cooler environment. Once our body temperature drops, our nervous systems quit sending signals and our brain stops ordering the suite of cooling activities.
All parts of a living system work together to maintain their organization by opposing change with every means at their disposal. This is how individual organisms work, and how ecosystems work.
This special ability to actively resist change is the essential quality that defines life from non-life. This ability is called homeostasis.
Through feedback, living systems are able to respond to change in their environments so they can:
Another example is when you cut your skin: blood, tissue, your immune system and behaviour all work together to mend the cut and return your skin to its original state.
Non-living things cannot actively resist change. Because of this, the resiliency of living systems cannot be effectively replicated by a human-engineered system.
Humans do engineer structures with feedback systems, for example, thermostats, car engines, computers etc. However these are comparatively very simple systems that are not self-creating or sustaining
For example, imagine that a bulldozer breaches a natural river channel with healthy deep-rooted riparian vegetation. Water floods through the breach and destabilizes the channel wall. Tree and shrub roots stabilize the bank around the breach, preventing it from getting much bigger. Over time, surrounding riparian vegetation eventually grows into the gap, their roots capture soil, and the channel wall is rebuilt.
Now imagine a bulldozer breaching a concrete water channel. Water floods through the breach. Over time, the concrete crumbles away, eroded by water flow, and the breach continues to get bigger. The channel cannot reconstruct itself because it is not alive.
The living and non-living components of the Battle River ecosystem have evolved together over thousands of years. The Battle River’s ecosystems and living things have evolved feedback systems that:
The second point means that life doesn’t just adapt to the non-living environment, it also changes the environment to make it more suitable for itself.
For example, riparian vegetation changes the local climate (microclimate) by creating shade and cooler temperatures. This reduces heat stress and water evaporation, ensuring that more water is available for plants.