Weak Link Biological

–   Does this action address the weakest link in the life cycle of this organism?
This test only applies to situations where there is a problem organism of some kind.  Although its application is vital when required, its scope is limited so don’t try to use it or force into other situations.    If it is not applicable, mark your testing form with 'NA', and move on.

There are two types of ‘problem’ that this guideline has application for. 
  1. The first is when a species is endangered.
  2. The second is when a population is growing rapidly, and at risk of becoming ‘out of control’.

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Endangered species
When an organism is threatened or endangered you can be certain that the population is declining because of a threat at the most vulnerable point in its life-cycle.  Any action you take to help it survive will only be successful if you are genuinely strengthening this vulnerable point.  At any other point the threat will continue to exist and the organism will still decline.

Example
In most species (but not always) the threat is at the juvenile stage.  The young are often born/hatched in normal numbers but are then either unable to find suitable food, or unable to find suitable protection.  

Sometimes the threat is to the young adults and sometimes the mature adult stages.  For instance, some populations of fish nearly collapsed before engineers worked out how to install ‘fish ladders’ around dams and weirs that were blocking certain species from returning to the only place where they would breed.  The structures enabled mature breeding stock to once again breed where, for millions of years, they had always bred.  

Over-abundance
A problem involving an over-abundant organism will most successfully be solved when the control actions are targeted at the weakest point in its life cycle.  This is seldom at the adult stage and is much more likely to be at their establishment phase.  

Examples
 Most ‘weeds’ are dicotyledon (dicot) plants.  That is, they have two leaves, whereas monocotyledons, such as grasses, have a single growing point.  Dicots are usually prolific germinators so if the moisture and temperature conditions are right they will germinate in abundance. Once a dicot emerges those two leaves must open outwards to ensure establishment.  Usually, if the ecosystem is degraded there is little to stop them opening out and they willingly and happily germinate, and then shortly afterwards open out and establish themselves.

However, these plants find it physically exhausting to push through a deep organic litter, and the deeper the litter, the fewer that will make the transition from germination through to an established seedling.  

I have seen many situations where, in just one season, farmers have laid down so much litter that paddocks that were previously described as ‘weed infested’ have few, and in many cases, no established weeds in them just a single growing season later.  All of this without mechanical or chemical treatment, but a significant application of human creativity, grazing and animal impact.

The same principle holds true for locusts.  Locusts require bare soil for egg laying.  If there was no bare soil there would be little risk of locust plagues!  History might have been different indeed.  Right now though, individual managers can make life difficult for locusts who think they might lay eggs on their land.  Cover the land in litter, and watch the locust's frustration at being unable to find an egg laying site!

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