Insect decline in the Anthropocene: Death by a thousand cuts

Annual Review of Entomology, 2019

Insect declines are being reported worldwide for flying, ground, and aquatic lineages. Most reports come from western and northern Europe, where the insect fauna is well-studied and there are considerable demographic data for many taxonomically disparate lineages. Additional cases of faunal losses have been noted from Asia, North America, the Arctic, the Neotropics, and elsewhere. While this review addresses both species loss and population declines, its emphasis is on the latter. Declines of abundant species can be especially worrisome, given that they anchor trophic interactions and shoulder many of the essential ecosystem services of their respective communities. A review of the factors believed to be responsible for observed collapses and those perceived to be especially threatening to insects form the core of this treatment. In addition to widely recognized threats to insect biodiversity, e.g., habitat destruction, agricultural intensification (including pesticide use), climate...

Global Decline of Insects [Working Title], 2021

Insects are the key component of world’s ecosystem and act as vital force to maintain life’s framework. But in present scenario, Insects are under multi-continental crisis apparent as reduction in abundance, diversity and biomass. The impact of decline is severe in areas which are highly impacted by human activities such as industrialized and agricultural landscapes. Habitat loss and degradation; intensive use of pesticides; pollution; introduction of invasive species and climate change are the most influential factors for their alarming decline and each factor is multifaceted. The accelerated decline in insect population can cause unpredictable negative consequences for the biosphere and is a matter of global concern that requires immediate and effective international collaborations. An urgent need is to identify the species at greatest threat; factors threatening their survival and finally the consequences of their loss. In order to maintain the integrity of managed and natural ec...

2019

In November of 2017, a group of researchers published a paper showing that since the 1980s, insect populations in protected areas in Germany have decreased by over 75 percent. The decline, dubbed by one reporter the "insect armageddon," was widespread, affecting sites on nature reserves across the country. It was also indiscriminate, affecting not just certain species, but overall biomass. In the following years, similar studies from Greenland, Puerto Rico, and locations in North America have also shown declines in number of insect species, abundance, and habitat. These declines have serious implications for ecosystems and for humans, some of which we can already see in effect, and some that scientists can't even predict to their full extent. This thesis will profile a research team in Costa Rica who are using caterpillar-parasitoid interactions to make estimates about insect population health, and explore the reasons for and extent of insect declines and their consequ...

Comptes Rendus. Biologies

Insects appeared more than 400 million years ago and they represent the richest and most diverse taxonomic group with several million species. Yet, under the combined effect of the loss of natural habitats, the intensification of agriculture with massive use of pesticides, global warming and biological invasions, insects show alarming signs of decline. Although difficult to quantify, species extinction and population reductions are confirmed for many ecosystems. This results in a loss of services such as the pollination of plants, including food crops, the recycling of organic matter, the supply of goods such as honey and the stability of food webs. It is therefore urgent to halt the decline of Insects. We recommend implementing long-term monitoring of populations, tackling the * Corresponding author.

Biological Conservation, 2020

Here we build on the manifesto 'World Scientists' Warning to Humanity, issued by the Alliance of World Scientists. As a group of conservation biologists deeply concerned about the decline of insect populations, we here review what we know about the drivers of insect extinctions, their consequences, and how extinctions can negatively impact humanity. We are causing insect extinctions by driving habitat loss, degradation, and fragmentation, use of polluting and harmful substances, the spread of invasive species, global climate change, direct overexploitation, and co-extinction of species dependent on other species. With insect extinctions, we lose much more than species. We lose abundance and biomass of insects, diversity across space and time with consequent homogenization, large parts of the tree of life, unique ecological functions and traits, and fundamental parts of extensive networks of biotic interactions. Such losses lead to the decline of key ecosystem services on which humanity depends. From pollination and decomposition, to being resources for new medicines, habitat quality indication and many others, insects provide essential and irreplaceable services. We appeal for urgent action to close key knowledge gaps and curb insect extinctions. An investment in research programs that generate local, regional and global strategies that counter this trend is essential. Solutions are available and implementable, but urgent action is needed now to match our intentions.

Insect Environment, 2022

Biologists and ecologists have been concerned about the worldwide reduction in biodiversity of many terrestrial and aquatic vertebrates. However, recently scientists have voiced similar concerns about invertebrate taxa, mainly insects.

Insect Conservation and Diversity

1. There is mounting concern over the conservation status and long-term trends in insect populations. Many insect populations have been reported to be falling and many species are threatened with extinction. While this is true, the evidence does not support unqualified statements of 'global insect decline'. Global environmental change does not affect all species equally, and there are clear winners as well as losers from anthropogenic impacts. 2. In this special issue of Insect Conservation and Diversity, we draw together articles that (i) identify key challenges in robust inference about insect population trends, (ii) present new empirical evidence for declines (and increases) in insect populations, spanning whole communities down to single species, in both aquatic and terrestrial ecosystems, and (iii) address the interacting drivers of population change, from empirical studies of environmental correlates, to experimental manipulation of driving mechanisms. 3. We argue that the way forward for insect conservation includes more nuanced language and approaches when communicating ecological evidence to peer and public audiences, beyond just a simplistic focus on the insect decline narrative. This will require an expanded portfolio of approaches to promote the value of insects to society, which in turn, should reinforce the social licence to prioritise insect conservation research. This should help us to deliver the rigorous science necessary to document ongoing trends and understand the drivers and mechanisms of population change. Only then will we be able to mitigate or reverse declining populations.

Nature Communications, 2022

Climate and land-use changes are main drivers of insect declines, but their combined effects have not yet been quantified over large spatiotemporal scales. We analysed changes in the distribution (mean occupancy of squares) of 390 insect species (butterflies, grasshoppers, dragonflies), using 1.45 million records from across bioclimatic gradients of Switzerland between 1980 and 2020. We found no overall decline, but strong increases and decreases in the distributions of different species. For species that showed strongest increases (25% quantile), the average proportion of occupied squares increased in 40 years by 0.128 (95% credible interval: 0.123-0.132), which equals an average increase in mean occupancy of 71.3% (95% CI: 67.4-75.1%) relative to their 40-year mean occupancy. For species that showed strongest declines (25% quantile), the average proportion decreased by 0.0660 (95% CI: 0.0613-0.0709), equalling an average decrease in mean occupancy of 58.3% (95% CI: 52.2-64.4%). Decreases were strongest for narrow-ranged, specialised, and cold-adapted species. Short-term distribution changes were associated to both climate changes and regional land-use changes. Moreover, interactive effects between climate and regional land-use changes confirm that the various drivers of global change can have even greater impacts on biodiversity in combination than alone. In contrast, 40year distribution changes were not clearly related to regional land-use changes, potentially reflecting mixed changes in local land use after 1980. Climate warming however was strongly linked to 40-year changes, indicating its key role in driving insect trends of temperate regions in recent decades. Being the most diverse group of animals 1,2 , insects represent a major part of Earth's biodiversity and contribute to essential ecosystem services such as pollination and pest control . Therefore, recent reports on their decline 5-7 raised major concerns in the scientific community 8 as well as among policymakers, stakeholders and the general public. Yet, the generality of insect decline across regions, ecosystems and insect groups remains a matter of debate . Also, we are only starting to understand what the main drivers of the observed trends in insect populations are 7 . To date, climate change and land-use change, including the intensification of agricultural practices such as pesticide use, are considered important drivers . As climate and land-use changes are expected to further increase their influence in the

Ecological Entomology, 2020

Recent authors have suggested that declines of insect abundance or diversity, documented first for particular insect taxa of high interest (e.g., butterflies, bees), may apply to insect diversity more generally. This has led to an urgent call for analysis of additional longitudinal datasets to examine trends in general insect diversity. Here we present a dataset gathered from 1982 to 2018 by advanced undergraduate students and graduate students enrolled in a taxonomy course that involved collecting as many insect families as possible over a 5‐week period at a high‐elevation protected forested site in the Sierra Nevada, California, USA. The data do not support any consistent gain or loss of family‐level richness between 1982 and 2018 (no linear trend); a non‐linear model suggested a possible small decrease in family‐level richness collected between 1986 and 1990, followed by a gradual increase from 1990 to 2018. Neither weather variables nor collector experience or skill appeared to ...