Os Fragmentos florestais e a riqueza de insetos em um ecossistema amazônico: sua importância nos sistemas de agricultura familiar

Abstract

One of the main causes of the worldwide loss in biodiversity is agrarian activity. Agriculture changes natural landscapes due to habitat loss and fragmentation. However, barring the expansion and intensification of activity in terrestrial ecosystems, with the aim of protecting biodiversity is unlikely. In fact, it is challenging to produce food and other consumer goods to serve an exponentially growing population without negative impacts on biodiversity. The use of arable land to answer the demand for consumption of food and other goods, due to population growth, make up most of the cultivated landscape. Land occupation is creating an environmental crisis due to the loss of global biodiversity, including the disappearance of insects. However, the accelerated reduction of insects worldwide seems to be disconnected from human well-being, so the negative consequences for humanity can be crucial. In this context, family-run agriculture can be a viable and sustainable alternative for species conservation. The activity occupies smaller areas, diversifies cultures, uses few external inputs, little or no technology and management is done by the family, among other aspects. Moreover, due to the fact of having 'close ties' to natural environments, it is usually more sustainable when compared to modern agriculture. However, the actual evidence does not seem so optimistic. Human livelihoods such as food production and other immediate ways to serve the economy are under serious threat due to the depredation of the biological diversity of insects. Pointing out the need to change the paradigm of large-scale production, such as extensive monocultures, to small-scale production based on the family farming model, seems to combine economic, social, cultural, and ecological functions. This thesis characterizes the insect community in family farming crops and its relationship with the distance from forest fragments in the surroundings. For that, we verified the pattern of richness and abundance of insects in areas of agricultural production crops, their relationship with the temporal variation during a cycle of temporary crops. We also checked whether the distance to forest fragments interferes with the wealth of insects in family farming systems. We conducted the study using the Malaise trap in ten areas of family production, in Colíder, Mato Grosso, Brazil. We collected 140 samples, 14 per location, 7 days of exposure in the field. We classified the distance between the crop and the fragment in two categories, being 200m (close) and 700m (distant). We divided the research into three chapters, to expand the knowledge of the importance of natural vegetation, as well as the diversification of cultures in agricultural systems. To summarize the existing information about insect reduction, habitat fragmentation, its positive effects on cultivated environments, we present in chapter I, the approach studied through the literature review. In chapter II, we characterize the insect community with dominance of rare, occasional species (singletons and doubletons). We verified that half of this community is in a little diversified group of herbivores with large populations. The other half is more diverse, composed mainly of predators, parasitoids, and pollinators in smaller populations. Two species, one non-colonial (Pieridae), undetermined, and another colonial (Labidus praedator, Formicidae, Hymenoptera), were the most frequent, occurring in 132 observations (94% of the sample). In chapter III, the distance to forested areas showed that insects in agricultural environments depend on these fragments of forest. However, regardless of species composition and distance from the remnant, the number of species has decreased over time, showing that the cycle of agricultural crops determines the richness and abundance of insects in agricultural environments.