Scientific Investigations Report 2006-5143 Table 2

Evaluation of Evidence Supporting the Effectiveness of Desert Tortoise Recovery Actions

By William I. Boarman¹ and William B. Kristan²

Scientific Investigations Report 2006-5143, published 2006.

Table 2

Relationship between observations of measures of effectiveness and the assumptions made.

[The rows in are arranged in order of increasing reliability. Each successive row includes additional observations that more strongly support the effectiveness of an action. See section 2.3 for further explanation]

Observation	Assumptions needed to conclude action was effective
An action is implemented to address a putative threat, but effect is not observed	Putative threat is really a threat, is the limiting factor, and the action removes the limitation.
An action is implemented to address a known threat, but effect is not observed	Threat is the limiting factor, and the action removes the limitation.
Reduction or elimination of a putative threat	Putative threat is a real threat and is the limiting factor.
Reduction or elimination of a known threat	Threat is the limiting factor.
Increased population size	Increased numbers are due to improved demographic performance, rather than re-distribution of tortoises, changes in observability, etc.
Improved demographic performance	Assumes that the change in survival and/or fecundity will increase the population, rather than increasing emigration, etc.
Improved demographic performance and increased population size	Assumes that the improvements create a viable population.
Improved demographic performance, increased population size, and viable population (Population Viability Analysis, PVA, observations over time)	None (recovery is observed)