Prioritizing the CWR checklist

Why do we need to prioritize CWR for active conservation?
The creation of a CWR national checklist is likely to identify a greater number of taxa than can be actively conserved due to resource limitations, especially if applying the broad concept of CWR (all the taxa within the same genus as a crop). Therefore, the process of establishing priorities for CWR conservation is an obvious and essential step in CWR conservation planning.

Beta macrocarpa Guss, a primary wild relative of and potential gene donor to cultivated beets namely of salt tolerant genes; it is Endangered (EN) at European level; here it is pictured in Quinta de Marim (Ria Formosa Natural Park, Portugal). (Photo: Maria Cristina Duarte)

There has been considerable debate about how species, in general, should be prioritized for conservation and about which criteria should be used (e.g. Fitter and Fitter 1997, Maxted et al. 1997). Possible criteria include: threat of genetic erosion, endemicity, rarity and population decline (Whitten 1990, Department of Environment 1996, Sapir et al. 2003), quality of habitat and intrinsic biological vulnerability (Tambutii et al. 2001), species abundance in relation to their geographical range size (Hoffmann and Welk 1999), “responsibility for the conservation of a species” (estimate of the geographic proportion of a species distribution in a certain country against the worldwide distribution) (Schnittler and Günther 1999), recovery potential, feasibility and sustainability of conservation (Whitten 1990), taxonomic uniqueness (Vane‐Wright et al. 1991, Faith 1992) and genetic distinctiveness, phylogenetic criteria and the ability of a species to speciate within "new" environments (Linder 1995), cultural importance (Norton 1994, Dhar et al. 2000), economic factors (Bishop 1978) and socio‐economic use, current conservation status, ecogeographic distribution, biological importance, legislation, ethical and aesthetic considerations, and priorities of the conservation agency.

Specifically regarding the establishment of CWR conservation priorities, several different criteria and numerous methods have been used depending on the needs and available resources of individual countries and/or the conservation agencies within the countries that are undertaking the prioritization exercise. Relatively recent studies have shown how CWR can be prioritized globally (Maxted and Kell 2009, Vincent et al. 2013), regionally (e.g. Ford‐Lloyd et al. 2008) and nationally (e.g. Maxted et al. 2007, Magos Brehm et al. 2010, Kell et al. 2015). At each scale, the economic value of the related crop (hence breeder demand), the potential utilization for crop improvement (i.e. degree of relatedness of the wild relative to the crop/ease of crossing with the crop), and relative level of threat are the most commonly used criteria (Barazani et al. 2008, Ford-Lloyd et al. 2008)—prioritization methods usually use a combination of all three of these criteria.

An alternative, and more flexible, approach is to assign different levels of conservation priority to CWR—still based on the selected prioritization criteria—rather than identifying a list of equally important priority CWR. The top priority CWR are thus a number of taxa for which it is reasonable to consider implementing active conservation. In this way, a more extensive list can be more easily and objectively justified, maintained and updated, and taxa that are not of immediate priority may be given conservation attention at a later date. In addition, by using this approach, some of the taxa that are of less immediate conservation priority may occur within the same sites as those of highest priority, so they could be captured in the same in situ CWR conservation sites and targeted when collecting higher priority taxa for ex situ conservation.

However, whichever prioritization methodology and criteria are used, the total number of target CWR should be adjusted to a number that can be actively conserved using available financial and human resources. There is no precise way of estimating the most appropriate number of target CWR and so any estimate will be subjective.

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Methods for setting species priorities

Methods for setting species priorities

Methods for setting species priorities

Numerous systems and methods have been used to set priorities for conservation. One of the first attempts was presented by Rabinowitz (1981) and Rabinowitz et al. (1986) where an eight‐celled table based on range, habitat specificity and local abundance was developed in order to evaluate different ‘types of rarity’. Other types of prioritization procedures include rule‐based systems, scoring schemes and ranking systems. An example of a rule‐based system is the IUCN Red List Categories and Criteria (IUCN 2001). This method consists of a series of rules that a species has to meet in order to fit in to a certain category, and can have two variants: it can be used to select those species that simultaneously fulfil ALL criteria (e.g. GP1B AND threatened), or to select those species that fulfil SOME of the criteria and so allowing some flexibility (e.g. ALL CWR THAT ARE EITHER GP1B OR GP2 OR threatened).

Scoring schemes use multiple scoring over a range of criteria to derive total scores for each species (Given and Norton 1993). This system has been applied to a wide range of plant taxa worldwide (e.g. Perring and Farrell 1983, Briggs and Leigh 1988, CALM 1994, Dhar et al. 2000, Sapir et al. 2003 and Kala et al. 2004). Scoring systems have also been complemented with multivariate analyses in order to identify groups of species with similar profiles (e.g. Given and Norton 1993), determine uncertainty values associated with some of the criteria—reflecting the extent of the existing knowledge, and thus their confidence in the estimates presented (e.g. Hunter et al. 1993, Carter and Barker 1993)—and to develop user‐friendly interactive databases (Hunter et al. 1993).

The weighting of the criteria is a variant of this type of method (e.g. Carter and Barker 1993, Lunney et al. 1996). The Department of Environment (1996) suggested the use of “individual weighting on each criterion in order to give some indication of the relative importance of that factor in measuring the extent of threat”. However, according to Carter and Barker (1993), in the absence of information suggesting which criteria may be more important in determining conservation priority for a species, it is better to keep the weights equal across all criteria.

Amongst the most widely applied systems is the biodiversity status‐ranking system (a variant of a scoring system) developed and used by the Natural Heritage Network and The Nature Conservancy in the US (Master 1991, Morse 1993, Stein 1993). Primarily, this priority‐ranking system has been applied to vertebrates and plants (Master 1991), where the species’ ranks were based on a series of criteria relating to species' rarity (number of individuals, number of populations or occurrences, rarity of habitat and size of geographic range), as well as population trends and threats. A scale—ranging from (1) critically imperilled to (5) demonstrably secure— was then used to assign a rank to each species at three separate levels—global, national and state/province (Stein et al. 1995). When these three levels were combined, the system allowed for a rapid assessment of the species’ known or probable threat of extinction (Master 1991).

Other approaches include that suggested by Coates and Atkins (2001) who developed a priority setting process for Western Australian flora where risk of extinction at population, taxon and ecological community levels was the primary determinant for setting priorities. The authors considered, however, that if financial resources are severely limited then further prioritization has to be undertaken based on taxonomic distinctiveness and ability to recover. Pärtel et al. (2005) proposed a new combined approach that focuses on species groups with similar conservation needs instead of individual species.

Source: Magos Brehm et al. (2010)

The Interactive Toolkit for Crop Wild Relative Conservation Planning was developed within the framework of the SADC CWR project www.cropwildrelatives.org/sadc-cwr-project (2014-2016),
which was co-funded by the European Union and implemented through ACP-EU Co-operation Programme in Science and Technology (S&T II) by the African, Caribbean and Pacific (ACP) Group of States.
Grant agreement no FED/2013/330-210.

Prioritizing the CWR checklist

Methods for setting species priorities