As the planet continues to warm, biologists are increasingly concerned about the dramatic declines in insect populations worldwide. Dubbed by some as the “insect apocalypse,” this global trend raises urgent questions about how these critical members of the ecosystem are responding to the rapidly changing climate. Biologists are striving to determine how different insect species will fare in the coming decades, aiming to predict the winners and losers in this evolving battle for survival.
A recent study, published in the journal PLOS Biology on January 30, 2025, sheds light on the complex ways in which climate change is affecting insect populations. In particular, a team of biologists focused on six species of grasshoppers in Colorado, revealing that the effects of climate change are not as straightforward as one might expect. The research, conducted by scientists from multiple prestigious institutions, provides key insights into how grasshoppers have responded to warming temperatures over the past 65 years.
The Rescued Grasshopper Collection
The study’s foundation lies in an unexpected treasure trove of historical data—a collection of 13,000 grasshoppers that was initially gathered between 1958 and 1960 by entomologist Gordon Alexander at the University of Colorado Boulder (CU Boulder). Alexander’s work, conducted in the Rocky Mountains near Boulder, was groundbreaking in that it documented the timing of six different life stages for these grasshoppers. However, after Alexander’s tragic death in a plane crash in 1973, the collection sat dormant for decades, preserved in 250 wooden boxes at CU Boulder’s museum.
It wasn’t until 2005, when postdoctoral researcher César Nufio rediscovered the collection, that the potential value of these specimens began to be realized. Nufio, recognizing the opportunity to use the specimens for a unique study on climate change, curated the collection and began a new phase of research. In the years that followed, Nufio and his team returned to the original collection sites, collecting thousands more grasshoppers, some from the same sites and others from nearby areas, to form a comprehensive dataset of over 17,000 grasshoppers.
How Grasshoppers Respond to Warming
The research team, which included Caroline Williams from the University of California, Berkeley, Lauren Buckley from the University of Washington, and postdoctoral fellow Monica Sheffer, aimed to understand how climate change over the last six decades had impacted the size and behavior of these six species of grasshoppers. Insects, being cold-blooded, are particularly vulnerable to temperature changes. They don’t generate their own body heat, so their body temperatures, growth rates, and development are highly sensitive to external environmental conditions.
Through meticulous comparisons of the historical data with new specimens collected between 2005 and 2015, the team was able to observe some interesting and surprising trends in the grasshopper populations. Many biologists had speculated that, with global temperatures rising, animals would evolve to become smaller in size to mitigate the effects of heat stress. However, the study’s findings challenged this assumption.
The Winners and Losers of Climate Change
What the biologists found was that the response of the grasshoppers to climate change was highly variable, depending on both their life cycle and environmental conditions. Some species of grasshoppers actually increased in size, while others shrank. The species that showed the most significant increases in size were those that overwintered as juveniles, known as nymphal diapausers. These species, such as Eritettix simplex and Xanthippus corallipes, could emerge earlier in the spring and take advantage of the growing season, benefiting from the warmer temperatures and abundant spring vegetation. These grasshoppers showed noticeable increases in size, particularly in lower elevation sites around 6,000 feet.
In contrast, the species that hatched in the spring from eggs laid in the fall, known as egg diapausers, did not benefit from this early-season advantage. Species like Aeropedellus clavatus and Melanoplus boulderensis—early-season egg diapausers—showed a decline in size, likely due to the earlier drying of vegetation in response to warmer temperatures. These species, particularly those in high-temperature environments, were negatively impacted by reduced food availability, which limited their growth.
Interestingly, the higher elevation species, particularly those found at altitudes up to 13,000 feet, did not show any increase in size despite experiencing greater temperature increases. This could be attributed to snow cover at higher altitudes, which delays the start of vegetation growth and thus limits the food supply for these grasshoppers. The researchers observed that while warming temperatures in lower elevations allowed some species to grow larger, the higher elevations posed different challenges that the grasshoppers were unable to overcome.
The Role of Elevation and Environmental Context
One of the central findings of this study was the role of elevational gradients in determining how grasshoppers responded to warming temperatures. While some species were able to take advantage of warming temperatures at lower elevations, those living at higher elevations did not fare as well. The snowpack and delayed spring greening in these high-altitude environments meant that food availability remained limited for the grasshoppers, preventing them from benefiting from earlier warm springs.
Moreover, the research team also conducted experimental studies in which grasshoppers were confined to cages at different elevations to better understand how they adapted to variations in heat and dryness. These experimental results helped support the team’s conclusions that grasshoppers’ ability to grow larger depended on whether they could take advantage of warming temperatures or were instead constrained by factors such as reduced food availability and the harshness of the environment.
Understanding the Complex Nature of Climate Change
This research underscores the complex nature of how different species—and even subgroups within a species—respond to climate change. While some species of grasshoppers are benefiting from the warmer conditions, others are suffering. Life cycle differences—such as whether a species hatches as an egg or overwinters as a juvenile—play a critical role in determining how a species will respond to changes in temperature and environmental conditions.
As Caroline Williams put it, “This research emphasizes that there will certainly be species that are winners and losers, but subgroups within those species populations, depending on their ecological or environmental context, will have different responses.” This nuance is crucial in predicting the impacts of climate change on ecosystems. The study also helps biologists refine the methods by which they make these predictions, ultimately improving our ability to respond to the consequences of climate change.
The Importance of Historical Collections
The study’s reliance on the historical grasshopper collection emphasizes the immense value of museum collections in conducting long-term climate change research. These collections allow scientists to compare historical data with current populations, providing a unique and irreplaceable record of how species have evolved over time. In this case, the CU Boulder grasshopper collection, initially compiled more than six decades ago, offered a rare glimpse into the effects of climate change on grasshoppers in the Rocky Mountains.
Such collections have become increasingly important for understanding the long-term effects of climate change. Similar studies on mammals, birds, reptiles, and amphibians have also used museum collections to track changes in species over long periods. For example, biologist Joseph Grinnell’s surveys of California’s wildlife, conducted between 1904 and 1940, have been crucial in documenting climate change’s effects on local ecosystems. By comparing historical and modern data, scientists can identify the most significant changes over time.
The Road Ahead
Looking forward, the research team is continuing to investigate the metabolic, biochemical, and genetic factors that contribute to the size changes observed in the grasshoppers. Understanding the underlying causes of these changes will provide further insights into how species adapt—or fail to adapt—to a changing climate. Additionally, future studies will help refine the predictive models used to forecast how different species might fare in the coming decades.
As Lauren Buckley noted, “Understanding what species are likely to be winners and losers with climate change has been really challenging so far… hopefully, this work starts to demonstrate some principles by which we can improve predictions and figure out how to appropriately respond to ecosystem changes stemming from climate change.”
This study is a crucial step in understanding how insects and other wildlife are coping with climate change, and it holds valuable lessons for future conservation efforts. As the planet continues to warm, predicting the winners and losers in the natural world will be essential for guiding ecosystem management and ensuring the survival of species that are critical to maintaining biodiversity and ecosystem health.
Reference: Insect size responses to climate change vary across elevations according to seasonal timing, PLOS Biology (2025). DOI: 10.1371/journal.pbio.3002805 , journals.plos.org/plosbiology/ … journal.pbio.3002805