A Platinum Rule for Prosperity: Diversity
Aspiring to be more eco-conscious can be dizzying. Should we concentrate on plastic pollution? Carbon emissions? Inter-generational justice? It can be pretty miserable to try to keep track of the consequences of our choices. In previous writing, I’ve taken the approach of exploring the impact of lifestyle choices on a suite of eight natural resources that are essential for human life including: fresh air, clean water, healthy soils, a stable climate, wilderness, biodiversity, oceans, and a toxicant free environment. After much research and thought, I realized that just one of these resources comprises the bottom line of pro-environmental decisions - biodiversity.
If a choice promotes biodiversity, it must also support the well-being of all aspects of an ecosystem, including my other seven resources. You can’t have a thriving biosphere if another aspect of an ecosystem is compromised. Perhaps the least obvious of biodiversity's dependencies is that we need a stable climate for a healthy biosphere. However, scientific research has shown that global warming above 1.5˚C, will almost certainly wipe out whole ecosystems, and reduce wild populations dramatically elsewhere. It is not the direct effects of rising temperatures that are likely to wipe out habitats, rather it’s the knock on effects. Rising global temperatures are leading to more hurricanes, more flooding, more drought, and more wildfires. Furthermore, 1.5˚C is a threshold beyond which there may be earth system tipping points (like melting of permafrost) which accelerate global warming. Indeed, this critical tipping point in the stability of our ecosystems is one of the main reasons why most countries have signed The Paris Agreement, which aims to keep global warming below 1.5˚C.
While keeping warming below this limit is essential for a healthy biosphere, it is not sufficient. As noted above, other aspects of the ecosystem need to be in good shape. It is as if biodiversity sits atop a precarious stack of other resources and if one is pulled out, biodiversity too will come tumbling down. But if we assure biodiversity is healthy, it follows that the other resources are healthy as well. Furthermore, a healthy biosphere is the reason why we want to protect our natural resources in the first place. The biosphere is life. Biodiversity is the queen bee of environmentalism. We need her, full stop.
But understanding the supremacy of biodiversity has taken a while to filter into my thought processes. I’ve recently been writing and speaking about strategies that will make gardens more climate resilient, yet it took two different articles (here and here) and one talk to realize that the “Biodiversity is queen” mantra works for gardening as well. On the path to that realization, I came up with four golden rules for Maryland gardeners who can expect more intense winter rainfalls and hotter drier summers: protect the soil, aim for dense plantings, nurture natives, and promote a wide range of plants. These are gardening practices that will help gardens to thrive under climate change. Like Maryland, many places on Earth are likely to experience more extreme weather events and hotter climates in coming decades, resulting in increased soil erosion, soil compaction, and soil desiccation. The best way to prevent soil damage is to nurture a diverse, dense, and native set of plants, the other golden rules of climate resilient gardening. Here’s why:
Diverse plantings have a range of root structures that help with soil retention, water redistribute, and opening up the soil pore spaces. A diverse plant community also promotes a diverse soil micro-biome, which in turn promotes a more diverse plant community. Diverse plant communities are more stable and resilient to perturbations and thus more suited to the uncertainties of climate change.
Dense plantings provide an umbrella that physically protects the soil from sun and heavy rainfalls, while creating more habitats. And perhaps somewhat counter intuitively, dense plantings experience less water stress because of increased humidity in the canopy and reduced temperatures. Dense planting also have more roots, helping with retention, water flow, and open pores.
Native plants are an essential part of gardening for climate resilience because they are adapted to the local average climate, as well as to unusual weather patterns of the region. It is very possible that the future average climate will resemble previously experienced weather patterns of today - though future extremes will undoubtedly test plants. But native plants, in any given region, will have further advantages over exotics having co-evolved and adapted to local soils, pests, diseases, and competitors. But their role goes far beyond their self-serving survival - native plants support and in turn are supported by the local environment - providing habitat and food for pollinators and other critters, opportunities for the reintroduction of a species from neighboring sites, as well as genetic options for coping with future stresses like climate change.
As you may have noticed, these golden rules of climate resilient gardening are all intertwined - supporting each other. Which got me to thinking: "Is there a keystone rule that underlies all these practices?” Then it hit me, and I was simultaneous delighted and slightly abashed to not have thought of it before. If we focus on fostering biodiversity in our gardens, we will also promote healthy soils and dense, diverse, and native plantings. My wandering path to this platinum rule for climate resilient gardening, also taught me that reframing is not always easy to incorporate into our thinking.
Refocusing on the centrality of biodiversity may well have ramifications for your behaviors, it has for me. On the global scale, I’m more focused than ever on food choices because food is the number one driver of biodiversity loss. And in my garden, I’ve used pesticides for the first time this season. I wouldn’t have applied this poison previously. But after many scratches and sore backs, I realized that I was going to loose a native forest community to invasive multi-flora roses and wineberries. I concluded that the one-off-application of tiny amounts poison (I just painted the pesticide on cut stems) would be less harmful to the local biodiversity than the loss of the native ecosystem. This focus on biodiversity, both in the garden and in my lifestyle, has simplified my approach to conservation efforts.
Coming to this same “Biodiversity is queen” conclusion, twice, also prompted me to question diversity more broadly. To my delight, I found that physicists have postulated that diversity in natural systems is an emergent property of the second law of thermodynamics. The second law of thermodynamics is a cornerstone of physics. It helps us to calculate how systems will evolve: where heat will flow, or how much work will be done. One way to articulate the 2nd law is the statement that all systems act to reduce gradients. Hot and cold water bodies will mix to a common temperature thereby reducing the temperature gradient. Trees collect high intensity sunlight and use the energy to make sugars, thus reducing energy gradients. Other creatures consume the plant’s sugars and redistribute them in ways that further reduce the solar energy gradient. As these gradient reducing processes go on, there will be new smaller energy gradients in a wide variety of settings that facilitate the evolution of life. The diversity of life may simply be the outcome of the different processes reducing energy gradients in an inconceivably wide variety of settings, and see here for a newer formulation of this idea.
The classic interpretation of the second law of thermodynamics is that all reactions increase the total entropy. Entropy is a sometimes thought of as an increase in chaos but in scientific terms it is a measure of the number of ways a system can be organized to achieve a given state. For instance, consider two bins of marbles. If the state is “one bin is full and the other is empty”, there are only two ways to achieve this: all the marbles are either in the left bin or they are all in the right bin. That’s not many states, and the entropy is low. But if there are an equal number of marbles in both bins, we can quickly see that there are many more ways to achieve this state . For instance the first 50% of the marbles may be in the left bin, or only the odd marbles are in the left bin, or many other combos. The equal marble distribution has many configurations to achieve the same overall distribution - it has high entropy. Seen from another direction, the system is more likely to be in the state for which there are more configurations. Even when there is a slight perturbation to the system, the system is again most likely to settle into the state with the most configurations. States with many configurations, or high entropy, are more likely and more stable.
In the case of ecosystems, high entropy states have plants and animals and fungi in many many niches where there was an energy gradient (e.g. sugars in a leaf or an animal that eat and may be eaten). In other words, high entropy ecosystems have a broad diversity of beings and are relatively stable systems. Other ecological considerations add to the stability of diverse ecosystems. If one population of a species dies, in a diverse system there will likely be other populations that survive - either by sheer luck or through genetic variability that enable adaptation to the new stress. Furthermore, a diverse system has redundancy - if all the tulip trees in my garden die, other trees will provide shade to the understory plants and habitats for birds. A diverse system supports more life - with more possible food chains, more water distribution pathways, more soil-fungal networks, and more micro habitats - which in turn increases the ecosystem’s resilience to perturbations. These traits of adaptation, redundancy, resiliency, and stability, mean that diversity increases the likelihood that the system as a whole will thrive. And this stabilization and vitalization of diverse systems seems to be true for systems beyond ecological ones.
Sociologists have found that having folks with different cognitive processes work together improves creativity, innovation, and growth. A mix of cognitive styles in a group also improves decision making - providing a broader array of perspectives and information as well as inclusion and well being and, unsurprisingly, leads to better uptake and outcomes. Companies with women and/or racial mixes in their top management teams have greater financial performance. One series of 5 studies found that increased racial diversity increased individuals likelihood of helping others. Agricultural diversification increases economic outcomes, reduces pest damage, and has substantial benefits for the wider ecosystem services like biodiversity, carbon sequestration, and water services. Can the second law of thermodynamics be harnessed to explain these benefits of diversity?
While it seems to be a widely applicable rule that diversity is good for a system’s function, resiliency, productivity, and stability, it is not necessarily the best state of affairs for all individuals. A monoculture of oak trees could be considered the best state for the propagation of oak genes, rather than a mixed diverse forest. Indeed, sociologists have found that increasing societal diversity can lead to friction and less cohesion. So even though the overall productivity of the ecosystems or society thrives under diversity, we would be wise to remember that for some, increasing diversity will be accompanied by loss. And a final humble offering on diversity: while I may not agree with others about X, Y, or Z, I will endeavor to appreciate how these differences contribute to a more productive and thriving society.