To keep a submarine live and moving in the abyss of open waters, you need various crew members able to perform various tasks. Probably most import of these are both the Engineering and Operations departments, however the importance of Weapons and Supply departments would vary under the different conditions. With three levels of redundancy (ie. three cycling groups of crew), there is also enough able crew members to share the load to keep the vessel running continuously.
In some cases, the result of losing one shift’s unit of crew – such as group 3 of Engineers – may have a sudden and noticeable impact on how well the submarine works, especially if a member of that unit is the only specialist for a certain piece of equipment or if the effort involved was strenuous and required adequate down time for recovery.
In other cases, removal of an entire department may not be noticeable for a complete deployment – such as Weapons – provided that no threats endanger the craft over the time period. In other cases, having the department there for the once a year event, is the difference between long term persistence and sudden and complete annihilation.
In yet other cases, losing one or two crew members may seem to have no noticeable effect at all – such as the loss of the primary chefs. However over time, there is a slow degrading of crew moral which is hard to quantify or to measure the effects of, but is ultimately debilitating to the entire mission.
If every crew member suddenly decided to only think of themselves, the vessel would be little more than a metal barrel on the bottom of the ocean, but collectively, their effort has radically effects as a whole.
How much could you reduce the size of the vessel as well, before it becomes too small to hold a fully functional resource of able crew?
This, in short, is a system that works very much like a simplified ecosystem. There are numerous specialists and generalists that are able to perform certain jobs that together make the whole systems a viable operation – the reasoning behind the importance of healthy biodiversity.
As with the engineers and navigators, it’s clear that with photosynthesis and pollinators, the benefits are obvious and profound. Without such processes oxygen concentration in the atmosphere would eventually decrease and also all primary food production would be lost.
When you look at storm surge protection provided by mangroves and forests, just like with weapons and supplies, the need may not be frequent enough for constant concern, but the risk in the absence of such services is too great to be ignored.
Some might argue that the loss of a species is excusable for the sake of progress. An example of such an attitude will be discuss in more detail in chapter eight, but it is common enough – ie. what is more important; a few hectares of remnant vegetation or a new shopping complex; the odd tree that provide a corridor for species movement, or maximising productive land; the presents of an insect or bird species or a new housing estate?
As with the loss of the primary chefs, the ramifications of losing a species, or reducing the environments capacity to hold as many individuals / species many not be noticeable for many years. New recruitment or distribution of plant species may reduce without obvious signs for many decades, due to the absence of seed dispersers and pollinators . Likewise, many animal species cause soil perturbation, assisting nutrient mobility and soil aeration, which can alter what species are able to live in that environment. Without such soil treatment, new seedlings are unable to grow and as older members of the plant community die off, the services that they provide are lost.
To keep an ecosystem alive and thus retain its useful functions upon the landscape, you need various species able to perform various tasks. Healthy biodiversity, with abundant redundancy, just as with the crew of a submarine, is the difference between viability and slow / sudden death.
 Catling, P. M. (2001) Extinction and the importance of history and dependence in conservation. Biodiversity. 2(3): 2-13