I photographed flowers this week! Ok, they were just flowers on the little speedwell plant (Veronica polita) that grows as a weed in our yard, but still. Flowers! My photography brain muscles were starting to atrophy and it was great to flex them a little.
Those flowers were a nice sign of spring. I’ve never understood why people point to the arrival of robins as a indication of spring since there are migratory flocks here during most of the winter, but it’s hard to argue with blooming flowers as a harbinger of seasonal change. It’ll be a while before most prairie flowers start to bloom, but the tiny blue blossoms in our garden are a great step in the right direction.
The other significant sign of spring in our yard this week was the big ol’ Woodhouse’s toad Kim spotted as she was cleaning up the landscaping around the edge of our house. The toad must have just recently emerged from its winter burrow because it still had dirt on top of its head. I was so excited to have a small animal to photograph that I took (no exaggeration) 270 photos of the toad as it sat cold and motionless in our yard. As a favor to you, I’ve winnowed that batch of photos down to the five that I’m including here. She’s just so pretty…
Cooler temperatures, and maybe even a little snow this weekend, will set us back a little, but spring is still coming… In addition to the flowers and toad, Kim also heard chorus frogs calling this week. Oh, and of course, the Platte River is full of migratory sandhill cranes – here for their annual spring staging event. Before we know it, prairies will be greening up and we’ll start to see and hear all kinds of activity again. Just…another…few…weeks…?
The phrase “let nature take its course” is so widely used
and accepted, it has gained idiom status.
The idea that nature is self-perpetuating and self-correcting is an
attractive one. The supporting evidence
is strong too – I mean, look at how long nature thrived before humans were even
Unfortunately, the romantic notion that we should just back
off and allow natural areas to manage themselves just doesn’t work in today’s
world. Or, to be more accurate, most of
us would be uncomfortable with the results of that strategy – especially at
individual sites. Whether you like it or
not, the earth today is heavily shaped and manipulated by human activity. Within that context, deciding to suddenly
back away and allow nature handle things on its own comes with some serious
repercussions. It’s akin to taking a
bunch of athletic kids, training them for years to be elite volleyball players,
and then entering them in a soccer tournament.
They might be great athletes, but they aren’t likely to fare well at a
tournament for which they don’t know the rules and don’t have the appropriate
skills to succeed.
This isn’t a post about what would happen to the earth if
humans suddenly disappeared. That story
has been told by others, and you can go explore and argue about that story with
them. This is a post about what happens
when we walk away from natural areas – prairies, in particular – within the
context of the world we inhabit today. I
also want to be clear that this post is not a criticism of the way humans have
altered the earth. There’s plenty to
talk about on that topic, but today’s post is about how we manage (or not)
natural areas in the contemporary world.
Let’s start by considering some of the ways in which humans
have altered the playing field for species and natural communities. We’ll focus on the grassland landscapes of
central North America because that’s the setting most familiar to me. First and foremost, we’ve converted much of
the landscape to intensive agriculture and other human developments. As a result, once expansive swaths of prairie
are now divided into small isolated fragments, limiting the ability of animals
and plants to migrate or otherwise move across the landscape. We’ve brought plants and animals from the
opposite side of the globe and released them into this fragmented
landscape. Many of those have become
dominant competitors, with the ability to eliminate other species from their
territories and reduce biological diversity.
The fragmented nature of today’s landscape facilitates
invasions, which most often occur along boundaries between prairies and nearby
land uses, such as roads, crop fields, suburban areas, or other areas where
invaders are established. Introduced
species are not the only invaders in this context, however. Native trees and shrubs, which have battled
prairie plants for dominance since the last Ice Age, have been given a huge
advantage. Instead of trying to spread
into prairies from a few stream valleys or other fire-resistant sites, they now
invade from countless locations – like an army that has dropped millions of
paratroopers behind enemy lines.
Within our fragmented landscapes, our agricultural and
industrial activities have increased the levels of nutrients such as nitrogen
and phosphorus – and those chemicals enter prairies through both the water and
the air. We are essentially fertilizing
prairies, which might sound positive, but usually favors invasive plants (e.g.,
reed canarygrass) or makes a few native plants exhibit the same aggressive diversity-reducing
traits as invasives. The inadvertent
fertilization of prairies is most intense in areas near crop fields or
factories, but the impacts are measurable even at great distances from those
Adding a rapidly-changing climate to all those other
stressors just seems unfair, doesn’t it?
We’ve introduced new enemies, provided them (and old foes) with access
points and increased competitive advantages, and carved up the landscape to block
escape routes and re-supply lines. Now,
we’re turning up the heat and quickly changing the basic growing conditions and
living environment within the prairies that have managed to survive to this
But, hey, prairies should be able to handle all that without
our help, right? (Good luck in the
soccer tournament, kids!)
Before we address that question, here’s one more
consideration. The last glaciers
retreated from central North America thousands of years ago, and tundra and
spruce forests gradually gave way to grasslands. During and after that transition, people have
been present and active managers of those grasslands. Human hunters influenced the composition and
behavior of animal communities, and arguably helped eliminate a number of
important animal species. Perhaps most
importantly, humans were actively using fire as a management tool (to attract
grazing animals, for example) as well as for warfare and other purposes. Those fires were an essential factor that
helped perpetuate grasslands and prevent them from being taken over by
encroaching woody vegetation. As a
result, today’s prairies have never been separated from people and human
So, what would happen to a prairie today if we decided to just leave it alone? It’s not a hypothetical question – any experienced prairie manager can tell you stories based on their own prairies, or on prairies they’ve watched suffer from insufficient or no management. The only fires that occur in today’s fragmented landscapes are those set by people. In the absence of those prescribed fires (or a substitute such as haying or grazing), prairies begin accumulating thatch – the dead stems and leaves from successive years of annual growth of grasses and wildflowers. Within a few years, that thatch begins to smother many of the plants trying to grow through it. It also creates inhospitable habitat for most prairie animals. Biological diversity, an essential component to the resilience and survival of prairie communities, decreases dramatically.
As thatch builds up, so does the competitive pressure from
invasive plants and trees. In my area,
for example, smooth brome, reed canarygrass and tall fescue tend to flourish in
the absence of management. They do
particularly well in high nitrogen environments, but they also get by just fine
without inadvertent fertilization. In
addition, there are numerous tree and shrub species that can quickly take
advantage of a lack of fire, including eastern red cedar, white mulberry, honey
locust, Siberian elm, smooth sumac, and rough-leaved dogwood. Especially in
highly-fragmented landscapes, those and other trees are often growing right on
the edges of prairies, and if not, their seeds can easily reach prairies by
bird, wind, or other conveyance. Complete
conversion of a diverse prairie to a woodland with a brome understory can
happen within a couple of decades or less.
You might be thinking, “well, sure, I can see how that might
happen in a tiny prairie surrounded by cornfields, woodlands, and suburban
sprawl, but what about some of the big prairie landscapes of Kansas, Nebraska,
or the Dakotas? Surely those prairies
can take care of themselves, right?“
We can argue about whether lightning fires alone would be
sufficient to prevent tree encroachment in a huge expanse of prairie. I feel confident they wouldn’t, but it’s an
argument that can be had. However,
invasive species, spurred on by nutrient pollution and climate change, are still
going to be a killer threat to biological diversity and the subsequent vitality
of those prairies in the absence of human management. Depending upon location, already-present
invasive plant species such as leafy spurge, sericea lespedeza, spotted
knapweed, cheatgrass, Kentucky bluegrass, and many others would expand their
reach and power to the point where they would dominate large swaths of land, if
not entire prairies. That invasion and
dominance would trigger a cascade of other impacts, leading to reduced plant
diversity, decreased habitat quality for animals, eventual extirpation of many
plant and animal species, and an ecosystem that would be unrecognizable – and undesirable
to most of us.
Anticipating protests, here are couple more quick
points. If you’re an advocate of the
broad idea that we should get out of the way and let nature take its course, you
might say prairies are an unfair example because they are a transitional
ecosystem that relies heavily on disturbances such as fire to avoid becoming a
woodland. That’s fine, but if you look
around the world, there are lots of other fire-dependent ecosystems, including
many (most?) forests and woodlands. Most
of those also have very long histories of human fire management.
In addition, woodlands and other ecological communities
suffer from invasive species, habitat fragmentation, nutrient overload, and
climate change, just as prairies do.
We’ve created a world that puts those natural systems at a disadvantage,
and whether we like it or not, they now rely on us to help mitigate those
threats. Arguing about whether human
management is natural or not is a
moot argument that distracts from the great challenges we face in conservation. Let’s focus on the important discussions
about how best to manage ecosystems, not the settled issue of whether we should
be managing in the first place.
People are an intrinsic part of nature and the world we live in. That shouldn’t make nature seem any less fascinating or inspiring – in fact, recognizing our interconnection with nature should inspire us even more. We are part of an incredibly complex and beautiful web of interacting species and communities across the glove. As such, it’s up to us to play our roles responsibly. Just as we don’t exist outside of nature, we also can’t survive without it.