Our Earth is one dot in this Milky Way galaxy where life, as we know, exist. This one dot is the only object in the solar system where life systems which include atmosphere, lithosphere, hydrosphere, and biosphere interact with each other to form a complex system which we call Earth System. Earth System i.e. our home, experiences billions and trillions of interactions between the components. These interactions have their own balance which is not well understood or not know. Awareness of such balance came as the last lesson in Human beings’ rapid acceleration after the industrial revolution. We human beings, as a community are trying to disturb this balance not at the regional level but at a global scale. Humanity has now the power that could bring changes at the regional level which could have a domino effect at the global level. We now have the power to change the face of the earth. This has resulted in calling this age as “Anthropocene”: The Age of Humans. Anthropocene has been the age of exploitation of nature and natural resources. Nature which provides ecological services is being overexploited. We have reached a point where we are hitting or about to hit thresholds mark at the global level. These boundaries are called Ecological boundaries. These boundaries have been set by nature and natural system but not so know to human beings. These boundaries are like tipping points. If we cross these boundaries, then there is no point of coming back. This means there will be irreversible change and we as a community will have to face catastrophic situations for which we are not ready yet.
Question is, are we there or not? If we are, will we be able to adapt to new reality? And if we are not there, could we possibly stop crossing these tipping points? Or should we just continue the progress of humanity by exploiting resources in business as usual? This brings us to the question of human growth and sustainability. Sustainable development has Economy, Society and Environment as its 3 pillars. However, there is growing evidence to prove that 3 pillars do have a cap and environment/nature will be the key in dynamically changing these caps. It’s also true that human prosperity and its distribution entirely depends on how environment pillar behaves in near future. There is a fundamental shift in thinking about limitless growth. Most countries have started to acknowledge the socio-ecological complexity that surrounds the human development. Challenge for most countries and humanity as a whole is to not just manages business or administration or states but bringing the desired development within the limit or caps which nature has put. Now science and technology have grown enough to recognize and quantify these caps. Efforts are being made all over the world to quantify these environmental boundaries and come out with a framework. In 2009, a group of 28 internationally renowned scientists quantified 9 boundaries within which humanity must continue its development. This framework came to be known as “Planetary Boundaries Framework”.
The concept of “Planetary Boundaries” revolves around resilience thinking. Resilience thinking provides a strategic framework for human development. Understanding of resilience would not only help understand abrupt changes but also helps in building capacity to deal with socio-ecological and economic shocks and stress. Now, what is resilience? A system’s (-be it a financial, ecological, wetlands, savanna- ) resilience determines its capacity to avoid flipping or tipping from one state to another. Resilience maintains the desired state of the system and hence keeps socio-economic development in a sustainable way. Societies have we speak are well embedded with these socio-economic-ecological systems. Any regime shift in these systems will create undesirable conditions for the societies. Each system involved both at the regional level and at the global level have tipping points, if system crosses this point then regime of the system changes, like rainforest turning into savanna after deforestation or lake turning into the dead lake due to eutrophication. For sustainable development its necessary not to breach any tipping points that could have catastrophic feedback both at regional and global level. As the world is getting more complex and turbulent, Concept of resilience has become more important than ever.
Earth has remarkably stayed within very narrow boundaries related to hydrosphere, atmosphere and biosphere. Global average temperature has stayed within 1 degree Celsius up or down. CO2 concentration has varied between 180-280 ppm and ecosystems have had stable regimes. There have been no large and rapid regime shifts in the entire Holocene era. However, there is growing evidence to prove that extreme events and ecological surprises are not predictable incremental changes but are more common and universal in character. These extreme events and ecological surprises are both effecting economies and society. The cost of this would not be just local but also both regional and global. One extreme event or one regime shift in one part of the world would create a domino effect at the global level. So to thrive in Anthropocene we need a new framework of human development which is defined by Planetary Boundaries.
In the geological history of the earth, there is evidence that Earth indeed has crossed tipping points on 3 occasions. 1st was some 55-100 million years ago, this was an extremely warm environment where the concentration of greenhouse can was high. 2nd was about 300-500 million years ago when the whole earth was covered in snow. 3rd was glacial and inter-glacial periods. There is growing number of scientist who believes that humanity by its very nature of unsustainable growth is pushing Earth towards these boundaries. It’s also true that Earth has bounced back from time to time however if regime shift happens its socio-economic system established by humanity that gone have catastrophic and cascading effect. And humanity and its systems are not prepared for the new regimes.
Planetary Boundaries framework starts by identifying process and systems that are associated with keeping the planet in the stable Holocene state. Each of these process and system will have identifiable threshold value and this would be based on best possible knowledge. These threshold values even though are hard to quantify, can be used as a reference point which must not be crossed. Planetary boundaries framework also takes a cautious approach towards planetary complexity by placing the safe boundary level at the lower end of scientific uncertainty. This would make the framework more adaptive to any governance system. Planetary boundary approach does not deal directly with human activities but focuses on the nature of Earth system itself. It attempts to define a safe operating space for humanity by respecting Earth’s own limits.
Identifying the critical element or process of the Earth System that determines the stability of the Holocene is the first step in setting up planetary boundaries. For each of process or critical element, we have an indicator that gives the state of these processes. These are called as control variables. The aim is then to identify threshold values for these control parameters and then to find whether our present system’s parameters are within danger mark or are they being crossed. Example if Climate Change is processed then control variable would be CO2 concentration. Scientists now are able to quantify threshold for CO2 concentration beyond which there would have +1 W/m2 in radiative forcing (which is unsustainable radiative forcing).
In Planetary boundaries, some have well-defined threshold and others don’t. There exist historical evidence to prove the same. Example, there is geological evidence to show shutdown of the North Atlantic thermohaline circulation(Gulf Stream), which occurred due to the addition of freshwater from melting of ice. There are other planetary boundaries that do not appear to show planetary threshold. One such example is bio-diversity loss, which will affect absorption of CO2 and hence influence Climate Change. These types are called slow variable. These slow variables have high resilience and thus provide intrinsic resilience to the earth system. Even though these slow variables are hard to quantify but these cannot be ignored. There is ample amount of evidence to show that gradual changes of variables like soil quality, biodiversity loss, the nutrient cycle can trigger abrupt changes when a critical threshold is passed. There are also some planetary-scale processes like climate change which will impact sub-planetary processes and sub-systems(which have a varying degree of sensitivity). Best example would be Climate Change impacting the Indian Ocean and El Nino Cycle.
Based on characters and keeping in mind the governance and management of these variables, Planetary Boundaries which are 9 in number, have been clustered into 3 clusters.
- The 3 big boundaries: This cluster includes Climate Change, stratospheric ozone depletion and ocean acidification.
- The 4 slow boundaries: This cluster includes land use change, freshwater use, the rate of biodiversity loss, global nitrogen and phosphorus cycles
- Human-Made Planetary Boundaries: Chemical Pollution and Aerosol loading.
Of these 9 Planetary Boundaries, Chemical Pollution and Aerosol loading have not been quantified yet. All others have been quantified on a global scale. However, research is going on to define at regional and local level.
The question comes, have we ever breached planetary boundaries or about to breach one. In mid-1980s scientist discovered shocking evidence of stratospheric ozone hole. Thanks to Montreal Protocol things are back on track. So one of the 3 big boundaries was once about to be breached. Still, steps are being taken under various protocols to stop emissions of gases that deplete the ozone layer. There is also evidence that CO2 level in the atmosphere is reaching a level which has never been that high in past 1 million years. There has been evidence of nitrogen and phosphorus loading which has crossed local boundaries and has caused an irreversible change in the ecosystems. Like one that was seen in Baltic Sea ecosystem and lake eco-system collapse in Europe and US. Another planetary boundary that has a history of being proven again and again is biodiversity loss. The collapse of fisheries in Newfoundland in early 1980’s is one such example of crossing regional bio-diversity tipping point. There has also been a case of the collapse of the ecosystem due to regional boundary set for freshwater usage. Best case being freshwater driven collapse in Lake Chad and the Aral Sea.
Monitoring is Key
Monitoring these 9 Planetary Boundaries and systems at the regional and global level needs a combined effort of varies branches of science including Remote Sensing. The science of earth observation could play a crucial and central role in this effort. There is numerous example of this kind of monitoring. One such example is Snow extent and snow cover. It is the good indicator for monitoring changing season and changing climate. It can be used to study shift in the pattern of snowfall which could lead to regime shifts. Snow melting is one of the crucial indicators of climate change (one of the 9 planetary boundaries). MODIS sensor onboard Terra and Aqua satellite are meant to collect various climate-related data. MOD10 is one of the MODIS products which could be used to constantly monitor shift of snow cover at a large planetary level. A lot of study is going on in understanding snow cover in Siberia and Eurasian belt using MODIS products. Study of Greenland ice sheet via remote sensing has become an important part of climate research. Hence mosaic datasets of Greenland (https://nsidc.org/data/nsidc-0547) have been provided for free so that researchers can use it for their studies.
Nitrogen and Phosphorus overloading are one of the human-made planetary boundaries which could trigger a lot of socio-economic regimes to shift. N and P loading triggers algal boom, eutrophication and eventually anoxic conditions in the water bodies. It’s easy to identify eutrophication and algal bloom using remote sensing both at the local level, regional and at the global level. For local and regional level high-resolution imagery data is used but at a global level lower resolution data and products of MODIS sensor can be used. Hyperspectral remote sensing would help in identifying the chemical composition of anoxic water bodies. Monitoring regional level water bodies would help in identifying source of the nitrogen and phosphorus overloading and would help in taking a sustainable measure which could have a positive impact on economy, livelihood and health of the region.
As explained previously LandUse and Freshwater usage will play a crucial role in maintaining the current desirable state. The various index like NDVI,NDWI,SMI which are derived from satellite images would give good spatial and temporal visualization of Landuse and water availability. High temporal resolution imagery providers like Planet (https://www.planet.com/company/) have the technology to constantly monitor the earth surface and fetch imagery every single day. Huge data sets of various sensor like MODIS,MEPOT are being used in predictive models to come out with the possible area that could be affected. Landuse change and freshwater usage boundary will impact livestock production, cultivation, soil erosion, regional climate regulation, food security and could also lead to social conflict. Hence it’s very important that remote sensing must be an integral part of the monitoring system which spreads across such a vast area and on such crucial things the define the very existence of human race.
Fisheries, coastal cities and coastal infrastructure are the one that defined 1 st industrial revolution. However, there is a threat that is staring right in the face of humanity. The threat of rise of sea level, rise of sea surface temperature(SST), ocean acidification has brought the sustainability meter to very low level. The collapse of coral reef system due to gradual heating of ocean is the biggest concern as these coral reef systems are rainforest for oceans. The rise of SST and ocean acidification are well connected and these combined with nutrient overloading is impacting fisheries, their diversity and eventually food security both at regional and at the global level. SST data like AMSR-E from AQUA satellite is one of the global scale product that was used to study global level changes of SST(https://climatedataguide.ucar.edu/climate-data/sst-amsr-e-sea-surface-temperature-remote-sensing-systems). MODIS/Aqua data on SST is freely available to analyze (https://neo.sci.gsfc.nasa.gov/view.php?datasetId=MYD28M). There is a constant monitoring of SST using MODIS and other geostationary satellites under various nations. And these datasets are being shared between various research stations so that there could a common climate change mitigation action plan.
In the world it’s not only the indicators are being monitored, there are some key systems like the polar region, worlds rain forest, marine systems, tropical savannas, temperate forests etc. which are also being constantly monitored. These systems are huge and spread across the huge geographical region to monitor as a centralized system. These systems also have a lot of regulatory functions like ocean circulations, SST, genetic diversity, carbon sinks, methane sinks, regional rainfall patterns etc. In order to monitor these systems and functions as a centralized system, Remote Sensing and GIS (Earth Observations) has come as a handy technology. A centralized control station for earth observation is being set up in various nations and Earth Observation would be the big part of it.
I was fortunate enough to receive “The Human Quest” book from Stockholm Resilience Center. This book introduced Planetary Boundaries and Resilience systems as a concept. Varies functions and system parameters defined in the book like LULC Change, evapotranspiration, coral reef bleaching, SST change, Brown Clouds, land temperature change etc. can be detected using satellite data provided by various satellites(MODIS, Doves of Planets, TRMM etc.). There is huge potential in research which combines Planetary Boundaries and Remote Sensing. Some examples being
- Detection of Algal blooms
- Thawing of permafrost at the regional level in Russia
- Change detection in Arctic and Antarctic ice sheets
- Biodiversity classification using hyperspectral remote sensing in savanna and rain forests.
- Study of snow cover extent in the Himalayan region and Eurasian region
- LULC change at the global level
These researchers are interdisciplinary in nature, which includes a team of experts from the respective domains that are involved. For countries like India where food security and water scarcity is prime, research is much concentrated around:
- Melting of glaciers in the Himalayan region and its effect on water availability at the regional level.
- Chemical pollution of water systems, fisheries
- Aerosol loading and its effect on health
- LULC change in the urban conglomerates
Most of the Indian research is concentrated towards remote sensing applications rather than understanding regional planetary boundaries for regional systems. There is huge scope and in-fact necessity to understand regional planetary boundaries at the regional level in order to have sustainable development within the boundaries. Earth by nature has immense resilience on its own, however, the system that we have built are very less resilience to any shift in the regimes. So either we let the systems change regimes and start adapting to new resilience or we need to stop systems before they cross the tipping points. Here is the real Quest.