The correct option is "1 and 3 only" because butterflies play a crucial role as pollinators for various flowering plants, and a decline in their population would adversely affect the pollination process, leading to reduced plant reproduction and diversity (consequence 1). Additionally, the decline of butterflies can disrupt ecological balance, causing a potential decrease in populations of species that rely on them or their habitat, such as wasps, spiders, and birds (consequence 3). However, the assertion that a fall in butterfly populations could lead to an increase in fungal infections in cultivated plants (consequence 2) is less substantiated and does not directly correlate with the decline of butterflies as a primary factor influencing plant health. Thus, options 1 and 3 align with the established ecological interdependencies highlighted in standard ecological studies found in NCERT materials.