Further, when the required data are readily available to include a larger number of CWR in diversity and gap analyses to identify populations and sites of conservation priority than have been afforded high priority conservation status, additional tertiary taxa may be targeted for conservation because they coexist with the high priority taxa. Due to recent concerted efforts in determining and documenting the relationships between taxa in food crop genepools Maxted and Kell, ; Vincent et al.
As for Criterion 1, consultation with the plant breeding community is worthwhile when selecting priority CWR taxa on the basis of their use potential, especially to gain the support of the user community for their conservation. Nonetheless, if consultation with plant breeders is viewed as an additional step in the process i. Criterion 3: The Threat Status of Wild Relatives of Priority Crops The degree to which species are under threat, relative to other species, is a fundamental criterion for conservation planning.
Assigning greatest weight to Criteria 1 and 2 in the CWR conservation planning process increases opportunities to conserve a broad range of genetic diversity of taxa with the most use potential for food and economic security. Following the process of applying the three criteria conceptualized in Fig. Attributing relative threat status to CWR is no different to any other wild taxa.
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The primary and most obvious means of achieving this is to categorize taxa according to their Red List status, either based on existing assessments published in national and regional Red Lists, as well as the International Union for the Conservation of Nature IUCN Red List of Threatened Species www. Although Red List assessment of CWR at the national level has not generally been systematically undertaken, some CWR species are included in national Red Lists because of their importance as threatened species per se, rather than as CWR.
If a published assessment is not available, a proxy for relative threat may be applied in the prioritization process by categorizing taxa according to their comparative distribution Ford-Lloyd et al. The comparative distribution of taxa can be seen as an indicator of the relative degree of threat when actual threats to populations or the habitats in which they are found are unknown, on the assumption that the overall populations i.
Using this approach, taxa with relatively limited distribution ranges can be afforded higher priority status than those that are more widely distributed. However, this measure should be applied with caution. First, although a taxon may be recorded as occurring in several countries, without knowledge of the actual distribution within those countries, we do not know how widely distributed the taxon actually is across its range.
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Second, because the aim of CWR conservation is to maximize conservation of infraspecific diversity, populations of taxa that are known to occur both inside and outside the country or region of the CWR conservation action should be actively conserved across their range. This approach does, however, include elements of gap analysis ex situ in the selection of priority taxa, a step ideally undertaken after taxon prioritization to avoid excluding important taxa in conservation planning.
Importantly, the status of a taxon as endemic should not be confused with its relative distribution. A taxon may be endemic to a country but widely distributed and not threatened, whereas other nonendemic taxa may have narrow ranges and may be threatened. Further, at the regional level, a taxon that is endemic to a small island cannot be compared with one that is endemic to a large continental country. Therefore, although it is understandable that countries and regions assign conservation priority to endemic taxa because of their inherent value to the country as unique national resources, emphasis should be placed on the actual relative distribution of taxa, not to their endemic status per se.
Kell et al.
First, the IUCN Red List assessment process does not take into account genetic diversity within and between populations, only population size and geographic range. As the goal is to maximize the conservation of CWR genetic diversity, it is vital that sufficient populations are actively managed both in situ and ex situ to provide an adequate sample of total genetic diversity Ford-Lloyd and Maxted, ; Maxted et al. Second, the criteria for assessing a species as threatened i. Third, although the regional Red List status of many CWR is likely to be Least Concern, many of these species may be nationally threatened.
In Europe, Kell et al. For example, when prioritizing CWR taxa as part of the national CWR conservation strategy planning process, the national Red List Status of species is clearly of upmost importance because prioritization is being undertaken at the national level. National endemic species that are assessed as threatened or Near Threatened are also regionally and globally threatened or Near Threatened, so highlighting this can add weight to the argument for their conservation, even if the regional and global assessments have not been published.
For example, in Europe, species regionally and globally assessed as threatened or Near Threatened that occur in more than one country include: Allium schmitzii Cout. Vulnerable and Asparagus nesiotes Svent. Endangered native to Portugal and Spain Santos Guerra et al. In general, taxa that are considered to be native are afforded conservation priority in any type of biodiversity conservation action plan, although archaeophytes—taxa that have been introduced to an area in ancient times commonly considered to be before AD —are frequently also considered to be of priority.
However, since some taxa are able to adapt rapidly to new environments Ford-Lloyd et al. Even if they arrive in their non-native habitat with a narrow genetic base, they are likely to rapidly evolve to their new environment and may contain unique diversity not present in the source population. In recent years, much progress has been made in planning CWR conservation at each of these three geographic scales. To inform ongoing developments, particularly in national CWR conservation planning, it is both relevant and timely to review approaches to CWR prioritization that have been undertaken to date and to highlight some common issues arising in the process.
National Approaches to CWR Prioritization Due to the sovereign rights of nations over the management and use of the genetic resources within their political borders, the responsibility to conserve those resources also lies at the national level. Therefore, national CWR conservation strategies, which aim for the systematic conservation of priority CWR genetic diversity in situ and ex situ, are fundamental to the effective global conservation of these resources.
The surge in projects and research focusing on the conservation of CWR diversity in recent years has resulted in significant progress in the development of national CWR conservation strategies, particularly in the European region, which has been a hub of developments in CWR conservation practice for the last 15 yr.
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Through the project PGR Secure, training in CWR conservation planning methods including prioritization has been provided across the region to build capacity and encourage action at the national level. Iriondo et al.
Notably, both authors highlighted criteria that countries have used which they consider to be supplemental to the three main criteria presented in this paper: i stakeholder priorities especially those of plant breeders , ii use categories, iii CWR of crops listed in Annex I of the International Treaty on PGRFA, iv relative distribution, v endemic status national and regional , vi geographical or regional responsibility for certain taxa with restricted worldwide distributions, vii rarity of the habitat in which the species grow, viii relative abundance, ix status in surrounding countries, x species listed in the annexes of the EU Habitats Directive, xi national protection status, xii expected effects of climate change on distribution, xiii occurrence status, xiv the center of diversity of the crop genepool, and xv ex situ and in situ conservation status.
In addition to the criteria listed above, the following criteria were used: i state of knowledge and availability of information, ii degree of genetic erosion, iii multiple or combined value, iv traditional use, and v use by local people as a food source. Untangling this array of different prioritization criteria applied by countries as part of the national CWR conservation strategy planning process is important to assist in future national efforts, both in systematically applying CWR prioritization criteria and in reporting on the methods used.
In Table 1, we address each criterion listed above in turn, commenting on those that can be considered integral to or as subcriteria of the three main CWR prioritization criteria presented in this paper, and on their relevance and value for CWR conservation planning.
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Labokas also highlighted the categories of crop use that were considered important in the prioritization process, noting that three countries Norway, Portugal, and Sweden prioritized taxa related to crops in six use categories: human food, animal food, forestry, medicinal and aromatic, industrial, and ornamental. This emphasizes the point made above that when planning CWR conservation and sustainable use strategies at the national level, crops in any use category may be afforded priority, depending on the inherent floristic diversity of the country and the economic value of the CWR diversity within its borders.
Sometimes a combination of these two methods may be applied. Both methods are valid but have limitations and potential pitfalls. Using the serial method, the order in which the criteria are applied effectively affords weight to each, and the resulting priority taxon list therefore reflects this weighting. For example, selecting taxa related to priority crops Criterion 1 , followed by selection of a subset based on relative threat status Criterion 3 , results in many taxa that may be of high value for crop improvement being excluded.
The same result would occur by selecting taxa based on their relative threat status Criterion 3 , followed by the value of the selected taxa according to the crops to which they are related. Therefore, when using the serial method of applying the criteria, Criterion 1 should always be the first one applied to ensure that the most important taxa are included in terms of their potential to contribute traits to the most socioeconomically valuable crops, and the practical likelihood that trait introgression from CWR is likely to be applied for that crop.
After the application of this criterion, the recommended approach is to apply Criterion 2 to identify the first subset of priority taxa, then to apply Criterion 3 to the remaining taxa, thus producing a list of priority taxa that are either of greatest use potential or considered to be worthy of conservation action because they are under threat of genetic erosion, regardless of their current known or potential value for crop improvement. This method is illustrated in Fig. Using the parallel method, all taxa in a national CWR checklist whether complete or partial are scored for each criterion and ranked according to their total scores to identify priority taxa.
This approach can be quite robust if very carefully planned and executed. However, there are two major potential pitfalls. First, the decision has to be made whether to afford equal weight to each of the criteria. Experience has shown that some countries tend to lend greater weight to relative threat status than to the socioeconomic value of the related crop or use potential for crop improvement, an approach that results in many taxa that may be of high value for crop improvement being excluded from the priority list. This problem may be compounded by including several subcriteria as described in Table 1.
Giving equal weight to these subcriteria effectively results in unintentionally affording greater weight to one of the three main criteria usually Criterion 3, because most of the subcriteria being applied relate to relative threat status. Second, the scoring system used is always subjective because it depends on the opinions of the practitioner undertaking the prioritization—although this subjectivity can be reduced to some extent through a process of review and validation involving national stakeholders, experts, and based on previous studies.
One solution proposed to reduce bias and subjectivity is to apply a number of different methods to the same set of species and then select the top 50 species in each of the methods to ensure that the priority species identified are those common to most methods Magos Brehm et al.
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However, this approach involves a significant amount of researcher time and may not be possible in most circumstances. In addition to these pitfalls, the work involved in scoring a large number of species is arduous and time consuming, whereas the more simple serial approach described in this paper can be relatively rapidly achieved by running queries on the base dataset. We therefore conclude that, while there is no single right or wrong way of undertaking CWR prioritization, the approach summarized in Fig.
Having made this point, practitioners must make a pragmatic decision on the best approach, which may be influenced by a number of factors including: i the particular nature of the conservation action e. Whichever approach is chosen, the number of priority taxa resulting from the exercise should not unduly influence the process. Although it is important to acknowledge that conservation agencies are forced to direct limited resources for conservation action where they are most needed and thus may be alarmed if presented a list of priority taxa as opposed to only 20, the rationale for maintaining a priority list, regardless of the number of taxa included, is twofold.
First, systematic conservation planning methods using advanced geographic information system GIS techniques aim to maximize CWR diversity conservation through action targeted at the minimum number of populations and sites. Second, if necessary, a priority taxon list can itself be prioritized to identify the highest priority taxa in most urgent need of conservation attention, while the remaining taxa may be considered for active conservation intervention at a later date.
In addition to the sources cited in this paper, there are a number of published case studies detailing the national CWR conservation strategy planning process, which practitioners can consult to help inform the choice of prioritization approach.