INTRODUCTION

An increasing number of recent studies describe a large and alarming decline both in insect biomass and species richness (Warren et al. 2021). A similar decline in butterflies has also been observed at a European level and especially in Central and Western European countries (Table 1). As a result, many butterfly species are now included in the IUCN Red List of Threatened Species.

Butterflies act as good bioindicators of the condition of the environment and the effects of human activities due to their quick response to environmental changes. In addition, it is a well-studied group of insects, as they are relatively easy for the general public to observe and identify. In many European countries, long-term monitoring schemes for butterflies take place with the participation of citizen volunteers (European Butterfly Monitoring Scheme), which provide valuable data on population changes and trends over time.

Butterflies have a complex life cycle; at each stage, which may last only a few weeks or months, they have different ecological requirements and rely on specific habitat characteristics for their survival. Their life cycle is separated into four distinct stages

(holometabolous insects): egg - larva (caterpillar) - chrysalis (pupa) - imago (adult). Larvae have very high energy needs and feed on specific host-plants. When their development has been completed, they find a safe and protected spot where they attach and remain for a short period of time in the stage of a chrysalis. Then adult butterflies emerge, which need sunny, open areas with flowers full of nectar and suitable micro-habitats for the females to lay their eggs.

The main causes of the population decline of several butterfly species are: the degradation and loss of natural and semi-natural ecosystems due to land use changes, agricultural intensification with the prevalence of monocultures, and the widespread use of pesticides and insecticides, as well as pollution.

Besides, poor or inappropriate management of agroforestry systems and in particular wood pastures and grasslands, which constitute the main habitats for many butterfly species, can also lead to habitat degradation. This can often be the result of either intensive grazing or abandonment of agricultural land, mainly in mountainous and semi-mountainous areas. In many cases, land abandonment leads to shrub encroachment at the expense of open ecosystems and grasslands that sustain herbaceous plants valuable for butterflies.

Grasslands are ecosystems of high productivity and economic value, and rich in species of butterflies and other insects. In the Mediterranean Basin they have principally been developed by the long-term presence of livestock farming and other traditional activities, and the maintenance of the latter is intertwined with the evolution of grasslands and the agroforestry landscape. Adequate management regimes, such as the application of extensive grazing or controlled mowing, can ensure grasslands of adequate and sufficient extent and of high quality, with suitable habitat characteristics for the butterflies. Likewise, in wood pasture systems, extensive grazing and targeted coppicing contributes to maintaining forest clearings, which are essential for the survival of many butterfly populations.