Changing Climate, Same Sensory Systems

Typically, when we talk about climate change and all of its associated effects such as the sea levels rising, droughts, and literal warming of the planet, we have a very human-centric point of view. We typically ask questions about the habitability of certain cities and the scarcity of natural resources but many times the general public overlooks the fact that we’re not the only life on Earth, therefore, we’re not the only life affected by climate change.

Many animals are highly adapted to their environments as a result of millions of years of evolution so this recent rapid change in climate has detrimentally altered these animals’ abilities to send and receive signals, sense cues and avoid predators. Alex Draper and Marc Weissburg at the Georgia Institute of Technology recently summarized these trends across 57 papers that focus on sensory shifts within predator-prey relations as a result of a changing environment.

They categorized these effects into two larger groups of indirect and direct sensory effects.

Indirect effects are changes to the metabolic processes of organisms such as the need to increase foraging or to migrate to a new location. These indirect effects result in an alteration of cues and the ability to send or receive signals as a product of other needs or behavioral changes. A specific example of this is in fish, crustacean, and sharks that have increased needs for nutrients for the same growth in a warmer temperature, which produces an increased vulnerability for fish who create cues when foraging, and for sharks to interpret their preys’ cues which is specifically resource-intensive due to their electrosensing systems.

Direct effects result in an alteration to the signaling and reception physiology as well as the efficacy of these signals within the environment. For instance, increased CO2 within the environment suppresses the response of Pea Aphids to alarm pheromones, because these CO2 molecules are a competitor with the active binding sites for their pheromone. In the ocean, these same elevated CO2 levels degrade coral reefs and alter the soundscape necessary for Clownfish to hear approaching predators.

Essentially, increased CO2 levels and warming cause cascading effects in the visual, auditory, chemical, mechanosensory and various other modalities which many prey rely on to detect predators and vice versa.

Strategic mechanisms for prey to avoid predations, such as camouflaging onto a similarly patterned background, have degraded in many instances like with fish now trying to blend into bleached Coral reefs. Efficacy modulation of the signals, which adjust the distance and speed of a signal so that only a certain receiver is able to receive the signal, has been altered as well making these modulations ineffective. This is particularly relevant in water as the speed of sound signals increases drastically for every degree Celsius the water heats up or cools down. And no modality is unaffected, chemoreception is altered by competing molecules in the atmosphere, and increased or decreased dispersion as a result of a warmer climate.

With this in mind, the more information that these organisms can derive from their environment the better chance they have of accurately decoding the information, therefore multimodal signaling is more resilient to the changes, yet, if the systems are adapted to a healthy environment, the translation of their information will be ill-informed in today’s context.

I know that this is a lot to take in and probably amplifies your current understanding of the severity of climate change, but it’s important to recognize these alterations to the sensory landscape so that we can predict the effects these changes will have on populations and try to mitigate losses in biodiversity and biomass.

Some may argue that this is just the natural way of evolution. The argument typically goes: “The environment changes and animals adapt”, yet, this vision is shortsighted as this view requires a balanced ecosystem. One example of the extreme unbalance that can exist within these ecosystems is the case of deer, specifically white-tailed deer in the northeastern regions of the United States. Currently, these deer are under-predated due to the overhunting of their natural predators. And because Deer are herbivores and eat anything they can find growing from the ground, they’ve overgrazed and have destroyed the diversity of forest across North America. These forests are now susceptible to the emerald ash bore, an invasive insect that kills ash trees by making nests in them. This cycle will continue and destroy countless forests across the globe without any sign of stopping. Imagine this scenario in a more insidious context in which a certain modality is hindered allowing for systematic over-predation due to our human interference. We may assume that this is just a natural byproduct of evolution but we’re the ones shaping the landscape.

From here I believe it’s critical for researchers to establish and monitor the baselines for these sensory systems on a frequent basis to determine critical shifts within ecosystems globally. These may be leading indicators of disruption rather than the lagging indicator of general biodiversity. Instead of the typical timespan of millennia to see changes in the landscape, these environments are shifting by the decade and year.

Draper, Alex M., and Marc J. Weissburg. “Impacts of Global Warming and Elevated CO2 on Sensory Behavior in Predator-Prey Interactions: A Review and Synthesis.” Frontiers in Ecology and Evolution, vol. 7, 2019.



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