Trophic downgrading of planet Earth.

Area of Science:

• Ecology
• Conservation Biology
• Ecosystem Dynamics

Background:

• Large apex consumers were once globally abundant, playing a crucial role in ecosystem structure.
• Human activities have led to the widespread decline and loss of these keystone species.
• The ecological consequences of apex consumer loss are increasingly recognized beyond ethical and aesthetic concerns.

Purpose of the Study:

• To synthesize current research on the cascading effects of apex consumer loss in various ecosystems.
• To highlight the broad and often unanticipated impacts of trophic downgrading on ecological processes.
• To underscore the need for interdisciplinary approaches to understand and predict ecosystem responses.

Main Methods:

• Review of empirical studies documenting the ecological impacts of apex consumer disappearance.
• Synthesis of theoretical frameworks regarding top-down ecological forcing.
• Analysis of diverse ecosystem processes affected by trophic cascades.

Main Results:

• Apex consumer loss triggers significant cascading effects across marine, terrestrial, and freshwater environments.
• These trophic cascades influence critical ecosystem functions, including disease dynamics, wildfire regimes, and carbon sequestration.
• Unanticipated impacts on invasive species and biogeochemical cycles are evident globally.

Conclusions:

• The disappearance of large apex consumers represents a pervasive human influence on nature with profound ecological consequences.
• Trophic downgrading disrupts ecosystem processes and resilience, necessitating urgent scientific attention.
• Interdisciplinary research is essential to forecast the future impacts of apex consumer loss on global ecosystems.