"Our house is on fire"

Greta Thunberg  (in an address to the United Nations, 25 January 2019)


Human society, as we know it today, evolved over the last part of the Holocene period. This period was characterised by an unusual degree of climate stability. We have now entered the Anthropocene, a period characterised by human alteration of the planetary systems which make Earth habitable for us humans. 


Our planet has also entered it's sixth epoch of mass biodiversity decline and extinction: this time brought about by the activity of humans.


David Attenborough narrated a documentary called "Breaking boundaries: the science of our planet".

The science described in this documentary, and its implications, are elaborated in Rockstrom, Johan and Gaffney, Owen (2021) Breaking boundaries: the science of our planet. Published by Penguin Random House. ISBN 978-0-7440-2813-3.


The essential message of the documentary and the book is that humans are rapidly eroding the life-support systems of planet Earth. 


The stability of the Holocene was underpinned by three major planetary systems: the climate, the ocean, and the ozone layer. It is these systems which together, with complex interactions and feedbacks, produced the planet's biosphere which nurtured the growth of human 'civilization'. 


The stability of the biosphere rests on system elements such as 

(a) the amount of oxygen and water vapour produced by the planet's biota, 

(b) the availability of freshwater in rivers, lakes and groundwater (and the biodiversity within that freshwater), 

(c) the temperature, circulation, biodiversity  and acidity of the oceans, 

(d) the spatial distribution and concentrations of nutrients, in both terrestrial and aquatic environments, and 

(e) the discharge into the biosphere of man-made substances, such as herbicides, pesticides, endocrine disruptors, ozone antagonists, toxic aerosols, and plastics*


Human activities are altering all these elements. 

Our house is on fire, yet there is little awareness of the danger the Earth faces at political levels.

Rockstrom and Gaffney argue that "we are in deep danger".  They call for the United Nations Security Council to initiate immediate and effective global actions to address the dangers which the planet faces.


It is noteworthy that our planetary crisis was ignored by almost all political parties in the 2022 Australian Federal Election.  


It is our children and grandchildren who will pay the price for our continued failure to face the danger.


The issue of identifying the planet's carrying capacity for humans depends on making complex assumptions about the impacts of individuals and society as a whole, as well as the value that should be placed on the other living inhabitants of planet Earth. There is no simple answer.  In my view, the planet overshot any reasonable definition of human carrying capacity around the 1970s.


I recommend the documentary and book to you all. 




Dr Jonathan C Nevill

19 May 2022.



* not in order of priority