Indicator species and umbrella species should be used with caution in conservation

Surrogate species are commonly used in conservation, and have a large influence on conservation decisions. It is cheaper and saves time to only monitor a limited amount of species, but does this approach work? Will conservation decisions and prioritisations based on the presence or richness of surrogate species have the intended effect?

One example of surrogate species are indicator species, where a high species richness of for instance birds is assumed to indicate a high species richness of other organism groups. Another example are umbrella species. For instance, large nature reserves are created to preserve the tiger, which have high demands of their habitat, with the assumption that these areas will also benefit other, less demanding species.

According to a review of previously published studies by Malin Tälle and colleagues, surrogate species are rarely useful in conservation. There are rarely strong correlations between the species richness of indicator species and other species, and conservation actions aimed at umbrella species will not uniformly benefit other species.

– But there are some situations when surrogate species can be more useful, says Malin Tälle, researcher at SLU: Such situations include when there are strong ecological similarities between species, for example when they are closely related or have similar habitat requirements, and also when more than one surrogate species group is used, for example both birds and mammals.

As surrogate species are rarely useful, it is very important to carefully select and use surrogate species in conservation, to ensure conservation actions have the intended effects. It is important to assess how useful a proposed surrogate species is, by testing if there are strong correlations between a surrogate and the species it is meant to represent.

– Biodiversity is a complex concept, so it is not surprising that it cannot be represented by only a few selected species. But there are few other options to using surrogates in conservation, as it is not practical to monitor all species. We hope that this study can be valuable in conservation, both for identifying situations when it is more likely that surrogate species will be useful, and help with identification of suitable surrogate species, says Malin Tälle.

Scientific article

The usefulness of surrogates in biodiversity conservation: A synthesis, Malin Tälle et al. Biological Conservation.

Different types of surrogate species

Indicator species are used to indicate the occurrence or richness of other species, for example threatened species, or to indicate areas with a high biodiversity. For example, the richness of birds are often used to indicate a high species richness of other species groups. Our review revealed that there are mostly weak correlations between the richness of indicator species and other species.  

Umbrella species are species that high requirements for their habitats, and these species are used as a basis to prioritise conservation actions. The assumption is that conservation actions aimed at an umbrella species will also benefit other, less demanding species. For example, nature reserves created to preserve the tiger are also assumed to benefit many other species. Our review revealed that conservation actions aimed at umbrella species will not always benefit other species.

Keystone species are species with a large ecological impact on other species in an ecosystem, in such a way that the loss of a keystone species will have negative effects on other species. Other species can be dependent on the presence of a keystone species or the habitats a keystone species create. For example, beavers creates dams that are important habitats for many species. Our review revealed that there are few reviews that have investigated the usefulness of keystone species in conservation, meaning it is difficult to draw any conclusions on their usefulness.

Flagship species are charismatic species that are used to collect funds for conservation actions, which will benefit less charismatic species. Often, flagship species are simultaneously used as umbrella species. For example, the giant panda is used to collect funds for conservation actions aimed at protecting habitats important for the panda, and many other species. Our review revealed that there are few reviews that have investigated the usefulness of flagship species in conservation, meaning it is difficult to draw any conclusions on their usefulness.

The higher-taxon approach is an approach where the richness of higher taxonomic levels is used as an indicator for lower taxonomic levels, to make monitoring more time and cost-efficient. For example, instead of identifying all insects to species level, they are only identified to family or genera. The assumption is that an area with many insect families or genera will also have a high insect species richness. Our review revealed that there often is a strong correlations between the richness of higher and lower taxonomic levels. The higher-taxon approach can therefore be useful in conservation.