Drift logs, a common sight along the shores of Vancouver Island and Haida Gwaii, are causing widespread destruction of rocky intertidal ecosystems, according to new research from the University of Victoria (UVic). While often seen as benign or even helpful, these logs are demonstrably damaging to marine life and contributing to declines in shorebird populations. The study, published in Marine Ecology, reveals a dramatic increase in log abundance over the past century, with significant ecological consequences.
Ecological Impact of Drifting Logs
The research, led by UVic biologist Tom Reimchen and students Esteban Pérez Andresen and Melanie Marchant, focused on the ecological effects of drift logs and their movement over time. The findings are alarming: over 90% of logs are displaced annually, and storms frequently cause extensive disruption to the intertidal zone – the critical stretch of beach between high and low tides.
This movement directly harms key species. Barnacle populations, a foundational element of the intertidal ecosystem, are 20–80% lower on surfaces exposed to logs compared to protected areas. The small invertebrates that thrive in the spaces between barnacles are also negatively affected. While barnacles settle each year, the cyclical movement of logs repeatedly removes them, preventing stable populations from forming.
Decline of Shorebird Populations
The damage extends beyond barnacles. Many shorebird species – including black oystercatchers, surfbirds, black turnstones, and rock sandpipers – rely on healthy intertidal zones for food. Researchers suspect the loss of barnacle beds and invertebrates due to log abrasion has contributed to a 50% decline in some shorebird populations since 1970. The instability caused by drifting logs directly impacts the food supply these birds depend on.
Dramatic Increase in Log Abundance
The problem isn’t merely ecological; it’s escalating. Reimchen’s team used satellite imagery and historical photographs to quantify log abundance from the 19th century to today. They found a staggering 520% increase in drift logs over that period. Even remote shores now have log densities comparable to more developed areas, indicating a pervasive issue.
Human Influence and Logging Industry
The study points to the logging industry as a major driver of this increase. Over 60% of analyzed logs showed signs of human origin, meaning they were directly or indirectly linked to logging activities. Even logs classified as “natural” may originate from landslides triggered by logging operations, demonstrating the far-reaching impact of human intervention.
Long-Term Consequences
Drift logs cause persistent and cyclical damage to the intertidal environment along the BC coast, and the problem has only gotten worse over the last century. The ongoing increase in log abundance, coupled with the ecological disruption they cause, poses a serious threat to the health and stability of coastal ecosystems.
The findings underscore the need for a deeper understanding of the long-term consequences of logging practices and the urgent need for sustainable forestry management to mitigate the destructive effects of drift logs on the fragile intertidal environment
