Abstract
Starting in the 1950s, agricultural production has been remarkably intensified, resulting in modern management systems where a severe increase in field size led to an elimination of edges and other ecologically valuable structural elements. The resulting habitat loss caused dramatic changes in natural communities. The aim of this work is to test whether there are statistically significant differences in insect abundance over time by using multifunctional margins that are seed mixtures of autochthonous species planted in combined strips, which are the fastest way to provide significant biodiversity benefits within farmed landscapes, enhancing the diversity and abundance of insects, birds, and small mammals, offering resources and reservoirs. This study was carried out in three intensive fruit farms in Spain over a three-year period (2013–2015). Each field was divided into two zones: the margin where a multifunctional margin was planted, and another that remained unchanged in the field. A clear trend to increase RTE species throughout the years in all farms was observed. Moreover, the margin showed a significant difference with respect to the field in the average number of insect species and individuals. The use of margins improves the appearance of RTE species in mean percentages ranging between 12.06 and 25.26% according to the sampling area. Margins also favour the increase in species (148.83–232.84%) and individuals (207.24–586.70%) in agricultural landscapes. These results clearly show that margins are an essential tool to fight insect decline in intensive farming areas.
Highlights
46 species were captured (31 from the field and 45 from the margin) from Alcarràs, of which 19 species are registered in the Red List (12 in the field and 19 in the margin)
The creation of multifunctional margins (MFM), banker plants, headlands, or hedges sown with a species-rich seed mixture has resulted in the fast recovery of insects, with biodiverse and abundant populations [37,51,82,83,84,85,86,87,88,89]
According to our first working hypothesis, the integration of multifunctional margins increases the probability of finding RTE species
Summary
Various studies show that the influence of changing agricultural practices since the second half of the 20th century negatively impacted species richness, abundance, and biomass, and led to shifts in species composition [6,7,8,9,10,11,12,13,14]. Reviews prove that six key factors are responsible for the biodiversity decline: (1) habitat loss, fragmentation, and degradation; (2) invasive species; (3) parasites and diseases; (4) non-sustainable use of pesticides; (5) extinction cascades; and (6) climate change [15,16,17]. Given the fact that these regions boast a long history of agricultural activity, it is likely that farming impacted the most sensitive species even before studies started to investigate such effects. It is not possible to claim that these studies are representative of what is happening globally [20,21], as intensive farming activities set in quite late in many tropical areas [19]
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