Forests and Insect Conservation in Australia by Tim R. New

Author:Tim R. New
Language: eng
Format: epub, pdf
ISBN: 9783319922225
Publisher: Springer International Publishing

6.2.3 Butterflies

Butterflies have major advantages in assessing environmental impacts involving vegetation changes, as a predominant herbivore group but also by being taxonomically tractable, diurnal, reasonably diverse, and surveyable by relatively simple and well-tried methods such as transect walks, timed observations, or fruit baits (the latter mainly for Nymphalidae).

However, whilst there is wide inference that that forest changes can have major harmful impacts on butterflies, methodological ambiguities can thwart comparisons between different studies. For example, Koh (2007) reviewed 20 studies on the impacts of land-use changes on forest butterflies in south-east Asia, all involving comparisons of butterfly species richness and/or abundance between forests and some modification from disturbance, such as clearing or selective logging. Seven of those studies found higher butterfly richness/diversity in the undisturbed or least disturbed treatments compared, nine studies found the converse (as the most commonly inferred likely outcome), three studies showed little difference across treatments, and the remaining one indicated a strong seasonal influence on logging impacts. Koh urged the need to determine the mechanisms that can influence the responses of butterflies to land-use changes: the clear lack of consensus amongst the studies then available implied considerable complexity in trying to predict the ecological features of individual species within each assemblage. Fruit-feeding butterflies in monoculture oil palm plantations and polyculture plantations (oil palm with interspersed other crops such as bananas, coconuts or sugarcane) in Malaysia differed little in species richness (Asmah et al. 2017). The same three species dominated both assemblages, in generally similar proportions ( Elymnias hypermnestra [monoculture 54.75%, polyculture 55.58% of total butterflies], Amathusia phidippus [30.84%, 28.14%], Mycalesis visala [8.94%, 12.56%]) and, despite the increased heterogeneity in polyculture plantations, this did not clearly enhance diversity of this selected butterfly group.

In accordance with an earlier study on butterfly extinctions in Singapore (Koh et al. 2004), where almost all the original forest cover has been lost, those butterflies most likely to go extinct were forest species with greatest host plant specificity, with probability of loss potentially increased for species with small geographical ranges. Perhaps only with that level of understanding can optimal conservation strategies be developed. More generally, reports that butterfly richness and abundance are less in plantations than in natural forest (oil palm in New Britain, Papua New Guinea: Miller et al. 2011), and also with forest conversion to natural shrubland (China: Li et al. 2011), exemplify the wider trends associated with forest losses.

Fragment size and vegetation influence the richness of butterflies present, and even very small isolated fragments in Sabah rainforest contribute to regional diversity (Benedick et al. 2006). Those forests, however, were relatively poor in species, and dissimilar to intact forest butterfly assemblages – significantly, no endemic species were found in remnants less than about 4000 hectares, although even the smallest remnants surveyed (one being only 120 hectares) supported species with restricted geographical distributions. Such remnants are highly susceptible to loss, as they are often disregarded and remain unprotected. Their importance for insects may be far greater than suspected initially.

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