Week 9: Planetary Boundaries Framework Pt. 4 - Post 1
Lecture 1 – Aerosol Loading – Dr. Sarah Cornell
-Aerosol is a rather technical term to describe the phenomenon of liquid droplets or particles, very small particles that are held suspended in the atmosphere.
-They can both absorb and reflect light, so they're important in Earth's heat balance, and in the climate system. They provide condensation nucleus points; water condenses on aerosol particles and affects where clouds are formed and where rainfall happens. And they also provide microsurfaces for chemical reactions in the atmosphere. So, they influence atmospheric chemistry. For example, the reactions leading to stratospheric ozone depletion, or the ozone hole, happened on polar clouds that formed on stratospheric aerosols in the upper atmosphere.
-Aerosols can be emitted directly into the atmosphere and they can also be formed through chemical processes in the atmosphere. That's what we call secondary aerosol.
+Primary Aerosol Sources: Oceans, fire, volcanoes, air blown dust
+Secondary Aerosol Sources: For example, plankton and land vegetation emit organic compounds that react in the atmosphere to make very small particles. These reactions that create aerosols that affect the distribution of clouds over forests and coastal zones.
-We also see human impacts in both direct and secondary aerosols. Land use change and combustion processes change the global patterns of dust and smoke emission. And together with transport and industrial processes we are currently changing the emissions of a very large number of chemical precursor gases that become aerosols in the atmosphere.
-Photochemical haze plagues cities like Shanghai and Los Angeles and many other mega-cities in the world.
-In other words, the composition and the ultimate fate of aerosols depend on many different geographic and meteorological conditions. This presents a major challenge to us when we're trying to find a global measure for what is acceptable or not acceptable in terms of aerosol changes in the Earth system.
-The human impact isn't just as simple as an increase in aerosol loading. In some instances human activities are removing or relocating aerosols. We risk setting off physical and ecological tipping points when we change atmospheric chemistry in this way.
-Aerosols are a vital part of the Earth system, and a dynamic part, and also that there's a huge amount of variability in their local and regional patterns.
-The net global effect is a cooling, at the moment. The climate planetary boundary already addresses the radiative forcing effect of aerosols. But there are good reasons to address anthropogenic aerosol directly in the planetary boundaries concept, in ways that address their physical and biogeochemical impacts, not just their effects on the global energy balance.
-Examples: where humans are causing regime shifts that might affect the whole Earth system is the change to the Asian monsoon system caused by the intense brown cloud of atmospheric pollution over south Asia and the Indian Ocean. Another is the change in tropical rainfall patterns caused when deforestation reduces the natural aerosol emissions from trees and its interaction with the water cycle. This change can trigger climatic and water cycle feedbacks that would accelerate regime shifts or tipping points from forest to grasslands. Also Cryoconite
-These kinds of pollution changes affect the regional albedo, and result in shifts in weather patterns, and biogeochemical flows, and ecosystems and the biodiversity within them.
-In summary, although there is no single value for a planetary boundary that incorporates all kinds of aerosols all around the world, there's a very strong case for specific sub-boundaries to be defined for particular aerosol systems in order to maintain the functioning of global earth system processes.
Lecture 2- Novel Entities – Dr. Sarah Cornell
-We now refer to the process as the release of novel entities into the environment. Why did we change the name? Well, first of all it signals that we're focused on the role of human-caused changes in the Earth system that can fundamentally alter the way that biogeochemical, ecological and physical processes happen at the global level. The changes we're concerned about are the ones where human technological capability lets us bypass the normal ecological and physical self-correcting, co-evolutionary behavior of living organisms interacting with the physical processes of the planet.
-There are many chemicals that have toxic effects, some of them like salt, or alcohol, or kerosene, or snake venom can be very toxic indeed, but they are dissipated in the environment because living organisms have co-evolved with the processes, the chemical processes, that produce them. Our human technical capability lets us put together chemical substances in combinations that did not exist before, and that no ecosystem has been adapted to, or can adapt to, on the time scales that we see for technological change.
“Novel Entities: Human technology has engineered fundementally new entities which have worked their way into the Earth system. These entities include synthetic chemicals that have not co-evolved with nature.”
“Novel Entities: Human technology has engineered fundementally new entities which have worked their way into the Earth system. These entities include synthetic chemicals that have not co-evolved with nature.”
“The concern over novel entities also relates to the human ability to mobilize natural toxic elements and transport them around the world”
Mercury –Example (above)
Example: Another very well known example is the problem of DDT, a synthetic pesticide that kills agricultural pests and mosquitoes, but many other organisms too. DDT accumulates in fatty tissues and so it can be carried through the food chain. It persists for years in soils and sediments. It has now become a globally distributed problem and it has fundamentally changed the way that ecological processes happen in the Earth system.
-We know that particular traits make novel entities a problem in the Earth system: Toxcity, persistence, global transportation, systemic effects, risk of irreversibility
-All of this means that we are still no closer practically to achieving a single quantitative boundary value for chemical pollution or these other novel entities. A major practical obstacle is the sheer variety of chemical substances, of radioactive substances, and of the many forms that these substances take once they've been released into the environment and are subject to chemical and biological changes.
-Precautionary Principle: Where there is a threat of significant reduction or loss of biological diversity, lack of scientific certainty should not be used as a reason for postponing measures to avoid or minimize such a threat.
- It requires new interactions between science, and policy, and business, and actually between everybody in society, because we're all exposed to these new global risks and we need to deal with them together.
Lecture 3- Synthesis and Progress on Planetary Boundaries – Johan Rockstrom
-So the planetary boundary framework is about safeguarding the desired Holocene-like state on Earth by recognizing this state as the only state we know that can support the modern world as we know it, and from science determining the Earth system processes that regulate this state. And that is what led us to defining the nine Earth system processes that we know, with the best science at hand, regulates the stability of the Earth system.
[And here we have of course the big systems with large scale tipping points, such as: climate change, ocean acidification, stratospheric ozone depletion. We have the four slow variables that operate under the hood of the Earth system regulating the ability of the large systems to be stable:land system change, fresh water use, the rate of biodiversity loss, and the way we interfere with the large nutrient cycles of nitrogen and phosphorus. And then we have the two processes that are so highly manmade: namely aerosol loading, which is all the soot and the particles in the atmosphere that cause large health challenges but also influences, for example, rainfall patterns and weather conditions; but finally of course the novel entities, the exponential growth of chemical compounds that aggregate themselves in the Earth system. By tapping on the best science we can put quantitative boundaries that gives us in green a safe operating place. This is where we can put humanity back, to prosper, develop, evolve, and thrive within this safe operating space.]
-Global Sustainability: planetary boundaries is a truly integrated analysis. It's about a safe space, and by biophysical terms, but it's about recognizing equity, fairness, and a just distribution of the remaining ecological space on Earth to enable a world of soon 9 billion people to develop and prosper.
*developments in the original theory:
- The first one is the recognition that the nine boundaries are not entirely, so to say, even in the role of regulating Earth resilience. In fact we do identify now that three of the boundaries are what we call core boundaries. They operate and regulate the entire Earth system, and they are the endpoint depending upon how the other boundaries operate. [Climate Change, Biodiveristy, Novel Entities]
Climate Change: So the best example of these three core boundaries is climate change. Climate change is the end result of how we manage fresh water, nitrogen, phosphorus, land, biodiversity, oceans. It all aggregates up into the functioning of the climate system. So when we use climate forcing as a good control variable for the climate system, the level of that forcing, whether or not we stay within the boundary, depends intimately whether we're able to stay within a safe operating space for the other boundaries,
Biodiversity: We now recognize increasingly that the genetic diversity on Earth, and the functions they play to sustain resilience and to build human well being, is a high level aggregate result of how we manage fresh water, land, oceans, nutrients, and even the climate system.
Novel Entities: The reason for this is that chemicals, such as everything from endocrine disruptors, persistent organic polluters, all the way to nuclear waste and loading of heavy metals, is so totally alien to the operations of the Earth system, in fact the Earth system has never seen, at least not in millions of years, the kind of human-induced artificial loading of new totally artificial compounds into the Earth system. We're learning as we speak what the aggregate effect of these can be on our own health, on the genetic composition of species, from birds to humans.
“It seems we need to stay within a safe operating space for every boundary in order to avoid that one boundary flips over across the threshold.”
-The second development is that we've refined the biodiversity boundary. We call it now biosphere integrity, because we recognize that genetic diversity is one thing which we captured in the first analysis. Basically what's the number of species on Earth, which we can measure quite well with extinction rate, which you used in the original analysis. Now we're much more, let's say, sophisticated in using a new index called the biosphere integrity index, which measures not only number of species but also their functions and how many species within each function.
-Phosphorous twin boundary- P in freshwater and P in oceans
-Nitrogen, new boundary – 44 million tons per year
-These are really exciting developments which enable the planetary boundary concept to be operational also at the local level, for a business, of a community, or of a nation's policies in terms of how to contribute to stay within a safe operating space.
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