Section 2.1: What is sustainability?
Section 2.2: Connections between humans & the natural environment
Section 2.3: Earth and its limits
Section 2.4: Major global (un)sustainability trends
Section 2.5: Climate change – the facts
Section 2.6: Welcome to the Anthropocene – It’s all about humans
The Earth has a limited carrying capacity. The carrying capacity is the maximum number of individuals of a given species that an area can sustain indefinitely, without fear of depletion, degradation or impairment to the natural ecosystem. If a carrying capacity is exceeded, there are two options: either the species adapts to new levels of resource consumption, or it finds alternatives for the resources required. If these options fail, then the system loses resilience and eventually collapses.
When we consider carrying capacity, we must distinguish between renewable and non-renewable resources:
– Renewable resources: Resources that can regenerate and replace themselves automatically via natural processes (also known as “flows”).
– Non- renewable resources: Finite, non-replaceable “stocks” of resources. The total supply of these resources remains constant, although we can replenish them through recovery processes such as recycling.
The Stockholm Resilience Centre considered the global carrying capacity of the Earth and identified nine planetary boundaries within which humanity could continue to develop and flourish into the future. The Centre highlights that crossing these boundaries is likely to result in abrupt and/or irreversible environmental changes, pushing our entire planetary system into a less hospitable state. A video thoroughly explaining this concept can be accessed here – Johan Rockstrom “Let the environment guide our development”.
As of 2015, we have crossed four of these planetary boundaries already:
– Climate change (CO2 concentration in atmosphere, and energy imbalance)
– Biosphere integrity (loss of genetic diversity in particular)
– Land-system change (deforestation)
– Bio-geochemical flows (the nitrogen and phosphorus cycles)
The factors that contribute to these boundaries are dynamic, but tracking them can help inform decision makers to define the safe operation space for humanity.
The biosphere integrity sphere is central to the planetary boundaries model. All other eight boundaries impact this sphere through the interaction of each boundary with biodiversity, as seen in the redrawn diagram below:
Coral reefs – A collapsing system
Coral reefs are among the most biologically rich and economically valuable ecosystems on the planet. An estimated $375 billion worth of goods and services are derived from coral reefs annually. Both climate change (rising sea surface temperatures) and other human activity (pollution, over-fishing, coral harvesting) are severely damaging coral reefs.
These threats have caused a rapid decline and permanent loss of some of these valuable and complex coral ecosystems. In 1998, a mass coral bleaching event damaged coral reefs globally and killed 16% of them. In 2016, reports stated that 93% of reefs in the Great Barrier Reef have been affected by coral bleaching, and that “if it was a person, it would be on life support” (see first and second videos). It is predicted if the trend of coral reef loss continues without time for recovery, a collapse of global reef populations and the services they provide can be expected by 2050.
Coral reefs are among the most biologically rich and economically valuable ecosystems on the planet. An estimated $375 billion worth of goods and services are derived from coral reefs annually. Both climate change (rising sea surface temperatures) and other human activity (pollution, over-fishing, coral harvesting) are severely damaging coral reefs.
Supplementary Resources
Steffen et al. (2015) “Planetary Boundaries: Guiding Human Development on a changing planet”
Corporate Sustainability Management 