Lecture 10 - Marine Strandings

Anthropocene

Current geological era in which human activity is the dominant driver of environmental change

Start of Anthropocene (hypothesis)

Often linked to industrial revolution (~late 18th century) and rise in atmospheric CO2 and CH4

Geological signal of Anthropocene

Distinct markers in sediments such as plastics, radioactive elements, and industrial pollutants

Human population growth impact

Rapid increase in population and per capita consumption driving environmental change

Major greenhouse gases

CO2 and methane (CH4), with methane having ~28x stronger warming effect per unit mass

Pollution as a global health issue

Leading environmental cause of disease and premature death worldwide

Air pollution key pollutant

PM2.5 (fine particulate matter <2.5 microns)

Effects of PM2.5

Linked to respiratory disease, cardiovascular disease, and reduced life expectancy

Water pollution major causes

Unsafe drinking water, poor sanitation, and industrial contamination

Eutrophication

Excess nutrients in water causing algal blooms and oxygen depletion

Environmental inequality

Pollution disproportionately affects low-income and marginalised communities

Cost of pollution

Reduces GDP, increases healthcare burden, and disproportionately affects developing countries

Evidence of pollution mitigation success

Clean Air Act reduced pollutants while economic growth continued

Climate change effects on ecosystems

Rising temperatures, ice melt, sea level rise, and increased extreme weather

Phenology

Timing of seasonal biological events such as breeding, flowering, and migration

Phenological mismatch

Timing mismatch between interacting species due to climate change

Example of phenological mismatch (hares)

Snowshoe hares become more visible due to coat colour mismatch with reduced snow cover

Example of phenological mismatch (bees and orchids)

Pollinators and plants become desynchronised due to different response rates to warming

Range shifts

Species moving to new geographic areas in response to climate change

Extinction risk from climate change

Up to 20–30% of species at risk under high warming scenarios

Highly vulnerable ecosystems

Mountains, polar regions, and cold-water marine systems

Marine plastic pollution scale

Millions of tonnes of plastic enter oceans annually, mostly from land-based sources

Sources of marine plastic

Rivers, waste mismanagement, fishing activity, and shipping

Plastic pollution as transboundary issue

Moves across countries via currents, requiring international cooperation

Economic problem of plastic pollution

Free-rider problem reduces incentives for individual countries to act

Deep-sea fishing impact

Trawling reduces abundance and affects species across depth ranges

Bycatch and ecosystem damage

Fishing removes non-target species and alters entire marine communities

Solutions to deep-sea impacts

Marine protected areas, gear restrictions, and depth limits on trawling

Ocean governance challenge

Requires international agreements and cooperation for effective management

Key idea of Lecture 10

Human-driven global change (climate, pollution, exploitation) is reshaping ecosystems and requires coordinated mitigation and conservation