# High prices for rare species can drive large populations extinct: the anthropogenic Allee effect revisited

## TL;DR

This paper revisits the anthropogenic Allee effect, revealing that increasing prices for rare species can lead to extinction even in large populations, challenging previous assumptions and highlighting new risks for conservation.

## Contribution

It extends AAE theory by analyzing a broader class of price-rarity functions, showing that extinction risk can be higher and occur in larger populations than previously thought.

## Key findings

- Higher Allee thresholds than classic theory suggests
- Large populations can go extinct due to price effects
- Even minimal prices can drive large populations to extinction

## Abstract

Consumer demand for plant and animal products threatens many populations with extinction. The anthropogenic Allee effect (AAE) proposes that such extinctions can be caused by prices for wildlife products increasing with species rarity. This price-rarity relationship creates financial incentives to extract the last remaining individuals of a population, despite higher search and harvest costs. The AAE has become a standard approach for conceptualizing the threat of economic markets on endangered species. Despite its potential importance for conservation, AAE theory is based on a simple graphical model with limited analysis of possible population trajectories. By specifying a general class of functions for price-rarity relationships, we show that the classic theory can understate the risk of species extinction. AAE theory proposes that only populations below a critical Allee threshold will go extinct due to increasing price-rarity relationships. Our analysis shows that this threshold can be much higher than the original theory suggests, depending on initial harvest effort. More alarmingly, even species with population sizes above this Allee threshold, for which AAE predicts persistence, can be destined to extinction. Introducing even a minimum price for harvested individuals, close to zero, can cause large populations to cross the classic anthropogenic Allee threshold on a trajectory towards extinction. These results suggest that traditional AAE theory may give a false sense of security when managing large harvested populations.