Population threat assessment

Assess the risks and external factors that could potentially threaten the target CWR population.

The ideal situation

Ideally, we wished that all target CWR populations were not threatened. That is, that they had population sizes that guarantee population stability in demographic terms and genetic diversities that do not compromise the resilience of the population due to processes leading to genetic erosion.

The real scenario and what to do

Often, the ideal situation above is not always the real scenario and CWR are under threat. For this reason, it is important to assess the risks and external factors that could potentially threaten the CWR populations. In particular, their chance to adapt to the effects of climate warming as well as their natural and cultural values.

Identify all threats to the target CWR populations in the genetic reserve, and design and implement a risk assessment.

Use the International Union for Conservation of Nature (IUCN) Threats Classification Scheme to assess all threats to the target CWR populations in the genetic reserve. For each threat, it is recommended that the timing of the threat (i.e. past, ongoing or future), its scope (i.e. the proportion of the total population affected) and severity (i.e. the overall declines caused by the threat) is recorded. Guarino (1995) provides a useful approach to measure the risk of genetic erosion.

Basic model for risk assessment

Steps to elaborate a risk assessment (Gardner and Davidson, 2011)

Step 1. Identification of the problem.

Determine if there is a potential threat and define the objectives and scope, providing the foundation for the risk assessment.

Step 2. Identification of the adverse effects.

Evaluate the likely extent of adverse change or impact on the genetic reserve and associated biotic community and ecosystem.

Step 3. Identification of the extent of the problem.

Estimate the likely extent of the problem on the genetic reserve of concern by using information gathered about its behaviour and extent of occurrence elsewhere. For instance, in the case of potential genetic pollution through gene flow from a nearby crop culture, it might include detailed information on the size and location of the crop culture, pollination and dispersal systems, and abundance of compatible pollination vectors and/or dispersal agents. While field surveys most likely represent the ideal approach, use of historical records, simulation modelling, and field and/or laboratory experimental studies all represent alternative or complementary methods of characterizing the extent of the problem.

Step 4. Identification of the risk.

Integrate the results from the assessment of the potential effects with those from the assessment of the likely extent of the problem, in order to estimate the level of adverse ecological change on the genetic reserve.

Step 5. Risk management and reduction.

Final decision-making process that uses the information obtained from the assessment described above and attempts to minimize the risks without compromising other societal, community or environmental values. Risk management not only considers the result of the risk assessment, but it also integrates political, social, economic, and engineering/ technical factors, and the respective benefits and limitations of each risk-reducing action. It is a multidisciplinary task requiring communication between site managers and experts in relevant disciplines.

Step 6. Monitoring.

Monitoring is the last step in the risk assessment process and should be undertaken to verify the effectiveness of the risk management decisions. It should incorporate components that function as a reliable early warning system, detecting the failure or poor performance of risk management decisions prior to serious environmental harm occurring. The risk assessment will be of little value if effective monitoring is not undertaken. The underlying concept of early warning indicators is that effects can be detected, which are in fact, precursors to actual environmental impacts. As such, early warning indicators can be defined as ‘the measurable biological, physical or chemical responses to a particular stress, preceding the occurrence of potentially significant adverse effects on the system of interest’. For example, the presence of natural pollinators in the target CWR population carrying pollen of a nearby cross-compatible crop could be an early warning indicator of genetic pollution.