The Late-Quaternary Extinctions Gave Rise to Functionally Novel Herbivore Assemblages

Area of Science:

• Ecology
• Paleontology
• Zoology

Background:

• Large mammalian herbivore extinctions over the last 50,000 years are hypothesized to have altered ecological processes.
• Quantifying the precise impact of these extinctions on past ecosystems has been challenging due to difficulties in direct measurement.
• Understanding these impacts is crucial for assessing long-term ecosystem health and function.

Purpose of the Study:

• To indirectly estimate changes in herbivore impact by comparing current and hypothetical no-extinction herbivore assemblages.
• To determine if changes in functional composition result in functionally novel herbivore assemblages.
• To assess the likelihood of biome state changes resulting from novel herbivore assemblages.

Main Methods:

• Quantified functional composition of herbivore assemblages using body mass, diet, and life habit for 502 wild herbivorous mammal species over the last 130,000 years.
• Compared current functional composition to a simulated scenario without extinctions.
• Assessed functional novelty and potential for biome state shifts based on assemblage composition.

Main Results:

• 47% of current large mammalian herbivore assemblages are functionally novel compared to a no-extinction scenario.
• Functionally novel herbivore assemblages have emerged globally, indicating significant shifts in herbivore impacts.
• On 20% of land, novel assemblages occur in regions susceptible to biome state changes.

Conclusions:

• Late-Quaternary extinctions and extirpations have fundamentally altered herbivore assemblages worldwide.
• These profound changes in herbivore composition likely have major consequences for ecosystem functioning.
• Novel herbivore assemblages may drive significant shifts in biome states in vulnerable regions.