When we think about our environment in terms of ecology, we're thinking about it in terms of a big picture.  It's one of the aspects of the science that makes it interesting.  We have specialized sciences for plant and animal composition, their behaviors, as well as the weather and climate around them.  However, by focusing on these individual aspects, we don't develop an understanding for how these pieces all interact.  And these interactions are incredibly important to how these species thrive and survive!

Understanding the whole picture of an ecosystem, the resources available, the volume of species inhabiting that ecosystem, and how much of those resources the species are using help paint a scene of how much of that system is utilized and what could possibly take up residence there.

​Enter the ecological niche, or the set of environmental conditions that a species lives and thrives on.

By John Severns (Severnjc) - Photo by John Severns., Public Domain, Link

For a frame of reference, consider a honey bee.  In order for the honey bee to live in an environment, it needs a certain amount of space, it has an ideal climate, it needs flowers that are pollinated in a way compatible with the honey bee, and locations where a hive can be constructed.  All of these are conditions necessary for the bee to survive, and that's certainly not an exhaustive list.  Other species may factor in abundance of trees, soil composition, amount of rainfall, altitude, and so much more.  It's really not a stretch to think that the combinations of variables are endless!

Needless to say, there's a bit to unpack here, so let's dive in!​

A History of Niches

One caveat before we start into this topic is that, while ecologists agree that niches are an important facet of ecology, there is also a general agreement that our understanding of niches today is incomplete.  We know that understanding the resources available in a community of species is integral to which species can thrive there, but the variability of communities is so high that our current models operate under a fair amount of assumptions.  With that said, let's see how we got to we we are today!​

Darwinian Beginnings

Niches were referenced in literature around environmental ecology since Darwin's contributions to ecological philosophy, but at that time, a niche was less about the conditions that a species is actually using in an environment, and more around a species' "destined" place in nature.  A good way to consider this thought is applying our human phrase of "line of work" but in the context of merely existing.  Especially in earlier human society, people were expected to keep in with the line of work historically done by their predecessors.  This concept was extended to nature as a sort of "line of life."  Species do certain things because that's what they've always done and are fated to do.  All niches are pre-existing facets of nature.

Niches, at their core, are the "spaces" a species inhabits.

This includes all factors of environmental need from food to space to climate.

Grinnellian and Eltonian Contributions

The Grinnellian view of niches took a step away from that notion by positing that niches are not pre-existing, but dependent on species adaptation to their environmental surroundings.  Many observations as ecology grew as a science shown that species often adapt to their available resources to find their niche.  This makes a lot more sense as pre-modern human era dispersal of species was reliant on a species durability to move around and find its niche.  More plainly, plants and animals couldn't move around the world as easily before humans started using ships and planes, purposefully or accidentally taking species with them.  Plants and animals have always exhibited a sort of resistance necessary to find there niche as their environments shifted.

For a while, humans considered niches to be destined "lines of work" for a given plant or animal

Eltonian views on niches were very similar to Grinnelian, but added that niches aren't just habitational, but depend on the species behavior as well.  It's not enough to examine the habitat, but how the species impacts that habitat by living within it.  A way to think about this is the resources needed for a beaver to thrive allow it to build dams that fundamentally impact the other species around it.  Functional actions upon an environment have ripple effects that, in turn, dictate available resources and niches available for other species.  It's probably worth noting that keystone species for a community are the easiest ripples to see, but they are by no means the only instance where this concept of the species itself being a niche variable can apply.

Like we said, there's a lot to unpack when everything is as interconnected as they are on our planet!

Hutchinson and Niches as a Hypervolume

One of the more recent contributions to niche theory is the Hutchinsonian viewpoint which clarified a few things about niches.  Up until this point, ecologists considered niches as a completely environmental aspect.  One of the ideas Hutchinson formalized was the thought that there are environmental niches in addition to a species' associated niche.  This concept split gave us the terms functional niche, the environmental potential that a species would ideally be able to thrive in, and realized niche, or the actual niche that the species lives with.  That might be a little confusing, but thinking of it like having a dream home versus the home that you live in is a decent approximation.  You would love to live in that optimal space, but you're able to work fine with what you have.

This concept also gave rise to maybe one of my favorite phrases with regards to ecology: niches are an n-dimensional hypervolume.  That is to say, niches are a set of possibilities that can be graphed on an object.  This could be points on a line, squares in a graph, or chunks of a 3D cube.  The "n-dimensional" describes the reality that niche possibilities can be arranged in any number of dimensions and "hypervolume" being a catch-all term for objects going beyond our concept of 3 dimensions.  Visualizing this concept is extremely difficult for humans to do, we experience the world in 3 dimensions and can at least understand 1-2 dimensions, but we have no experiential framework to understand 4 dimensions and beyond.  This doesn't mean the concept doesn't exist, just that we can't fathom what it looks like!

Functional niches are the ideal range of needs for a species.

Realized niches are the actual niches filled by a species.

Math lessons aside, niches can be thought of as intersections of multiple factors.  Things like species size, number of trees, soil composition, how often it rains, average temperature, amount of direct sunlight, etc.  Each of these aspects can be charted as dimensions on a graph and plotting which intersections are ideal for a species.  These graphs give us approximations for what kind of species could live in which ecosystems.  Due to the difficulty in plotting for beyond 3 dimensions, though, that's the best the model provides: an approximation.  These are still immensely helpful for building an understanding for a species full range of functional an realized niche potential!

Modern models posit that niches exist on an n-dimensional hypervolume, where the possible combination of niche factors are potentially endless!

Niche Theory Today

While those contributions happened in the 1900s, a lot of our thoughts on niches are derived by those concepts today.  There has been a fair amount of discourse on our small-scale view of niches being adequate in fully understanding the concept in nature, but there is still general agreement that the concept is integral to how our planet functions.

One big point of contention is that historic niche theory has a pretty big dependency on a concept called competitive exclusion, or the idea that a niche cannot be occupied by 2 species in a single community.  Essentially, if 2 species are vying for the same resources, one species will "win out" over the other, forcing it to either adapt, migrate, or die out.  Observations show that this is true especially in today's high human dispersion of species throughout the world.  This starts delving into the topic of "invasive species" or species introduced to an environment that have harmful impacts on the historic species in the community.

However, in stable environments, some believe that it would be better to view the community in a different way, called neutral theory.  Rather than observing the ecosystem's species as a whole, by observing it in groups of "identical" species, you don't see competition, but what is called dynamic shift, the thought of species changing behavior or the community succeeding to a form that better suits it without the need for competition.  Models using this view can be fairly accurate for very small community sample sizes, but fall apart at larger scale or if any species is introduced or migrates into the community, where the competitive exclusion model ends up winning out as more accurate.

​This isn't to say our current niche theory is foolproof or that neutral theory is not worth examining.  As humans move more into an equal fitness, non-competitive (ideally) society, this lens may help us understand a post-competitive exclusion environment.

Humanity & Niches

Speaking of humans, how does this all impact us?

Thinking about niches as an observation of ecology, we have a lot to learn from seeing the world in this way.  Understanding that resources are finite in a given area, there is only so much that can thrive there.  Knowing that not all species are vying for the same resources gives us a greater feel for what factors into any ecosystem's potential for biodiversity.  Being able to foster and protect diverse environments ensures that the Earth's systems are being utilized by its inhabitants, which everything on the planet benefits from!

In a nutshell, thinking of niches gives us a deeper understanding of how species on our planet are connected.  It's safe to say that humanity has altered the Earth quite a bit, and by understanding the exact things we disrupt, we can learn how to identify historic states of the Earth and set ourselves on trajectories that let biodiversity take hold again.  Of course, it's never as easy as aiming for what once was.  Over the course of changing our planet, we have likely altered it in ways that simply thinking in terms of "how it used to work" will never be enough.  By learning the core concepts of why ecosystems work and thrive, we can set new goals learning from our past and how we changed things.

Even though humans generally exist outside of the concept of ecological niches, we seemingly adopt aspects of niche theory in our societies, like finding a career that best suits our abilities.

Guess it's difficult to break from old habits!

​Beyond learning about our environment, humans have also adopted a form of niches in a societal sense.  While we don't necessarily compete for resources on a community level, we do compete as a society.  Our rules are a bit different, more self-made than fundamental restrictions.  Say for instance, you're looking to start a career.  You will identify your existing skills and what you would like to learn to achieve your goals.  You're identifying your fundamental niche.  Your ideal skill set and environment to succeed.  When you land your first job, you're realizing your niche by finding something that overlaps as much as possible with your ideal state.  This is a loose analogy, but can certainly be drawn from how we would operate in a world where resources outside of money were on the table.  We never quite get away from these concepts and apply those inherent frameworks to how we function in a society as opposed to an ecological community.  Pretty interesting to think about!

So, while niches seem fairly straightforward, the resources and environment a species needs in order to thrive and the realization of that ideal, there's a lot of nuance that goes into the concept.  At our best, we end up with approximations due to our inability to grasp the bigness of our planet's connectedness.  Though, at the end of the day, simply understanding that this connectedness exists and that we're all just finding ways to live in a constantly fluctuating world is a still a step in the right direction.  And any step to a better understanding is a step worth taking.

~ And, as always, don't forget to keep wondering ~

Sources
* Pocheville, Arnaud (2015). "The Ecological Niche: History and Recent Controversies". In Heams, Thomas; Huneman, Philippe; Lecointre, Guillaume; et al. (eds.). Handbook of Evolutionary Thinking in the Sciences. Dordrecht: Springer. pp. 547–586. ISBN 978-94-017-9014-7.​

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