Recently I've been thinking about how ecological communities adapt to rapid change. Ecological communities are defined by combinations of plants and animals found in a specific environmental context. The Hemlock Forest contains a half dozen or so different community types (see the NYS Natural Heritage Ecological Communities Site) with names like, "Hemlock-Hardwood Swamp" and "Appalachian Oak-Pine Forest". At the scale of an ecological community rapid change can result from events such as a fire or from someone digging a ditch to drain a wetland. Or it can unfold more slowly such as when an aggressive non-native species becomes established in an area altering the established mix of plants and animals. Rapid changes unfold on time scales that we can see; a day, a month, a few years. But even change that takes place over a decade or two is barely a smidgen of an instant in terms of geologic or evolutionary time scales. From the perspective of geologic time, humanity is altering the ecological systems on the earth at a pace that resembles a great natural cataclysm. Much like when that famous asteroid struck and killed the dinosaurs or when a super volcano explodes and alters the composition of the atmosphere. We are running a gigantic experiment on the earth's systems by rapidly altering ecosystems at every scale.
Ecologists study these sorts of things but the pace and scale of the changes taking place now far outpace their (our) capacity to understand what is happening. We have put into motion changes that will produce a range of effects that future generations will have to deal with and our children and grand-children will probably be forced to manage and repair natural systems in ways that we really can't imagine (did you grandparents imagine the world we live in today?). To do that they will need to know as much as possible about how these systems worked before we messed around with them. Information is the key and our technologies, the same ones that have the potential to be our undoing, might also save us. These days, anyone with motivation can add to the data that might really matter to those working on these problems in the future.
Of course, access to tools doesn't mean that acquiring useful data is simple or obvious. What data is valuable? How do you actually get it? How do you manage it? These are among the questions that motivated me to create this blog. I don't have all the answers but maybe I can add something that is part of the solution. Whatever you figure out, please share. Unlike most ecosystems I can adapt rapidly when a better idea comes along.
The Plan
I live in the northeastern United States where some of the most interesting ecological communities are the wetlands: swamps, marshes, fens, bogs and so on. The Hemlock Forest area contains several different wetland community types in close proximity to each other. Image One shows a flooded forest (more formally a Red Maple Hardwood Swamp). Image Two shows a Perched, Swamp White Oak, Swamp. It's a perched swamp (the defining environmental characteristic) dominated by the Swamp White Oak (species). Interestingly, this community type is considered to be rare in New York State. It's not that the individual species are rare --Swamp White Oaks are fairly common-- but the perched swamp environment has brought together an uncommon combination of species. Image three shows a third wetland type present in the Hemlock Forest; your basic Hemlock-Hardwood Swamp.
Image One: The Hemlock Forest includes several different types of wetlands. The area pictured is a Red-Maple Hardwood Swamp - often referred to as a flooded forest. The species mix present in this area has been altered by the rapid spread of non-native plants and shrubs and also by past attempts to drain the swamp.
Image Two: The Perched, Swamp White Oak, Swamp area. It is a perched swamp because the surface water is disconnected from the water table by a layer of impermeable clay. The characteristic species is the Swamp White Oak; The large tree on the left is a Swamp White Oak.
Image Three: The forest contains numerous small Hemlock-Hardwood Swamps. The trees in the foreground are Hemlocks and the entire forest area is named after the stand of old growth hemlocks present in the northern half of the preserve.
The varied ecological communities present in this 300 acre forest make it appealing as a place to learn more about how ecological communities adapt to the introduction of aggressive non-native species. I've focused on plants and shrubs because they are relatively easy to identify and the Hemlock Forest area has significant populations of several non-native shrubs and vines including:
- Asiatic Bittersweet (Image Four)
- Japanese Barberry
- Burning Bush
- Japanese Knotweed
Image Four: A tangle of Asiatic Bittersweet vines. This aggressive invader is present throughout the forest where ever there is a break in the canopy.
Other invasive plants, shrubs, and trees (and creatures of various types) are present but these four spread rapidly and alter the composition of existing native communities. This raises additional questions, including:
- Why are these species so successful? Not all introduced species out-compete natives species or spread so rapidly
- To what extent, and how quickly, do native species adapt to these newcomers?
- Do non-native species alter established patterns of succession within native community types?
- Are there effective control methods for these species? And, if the makeup of a community has been altered by the established presence of non-native species, what effects might come from "controlling" the invader(s)? In other words, can "controlling" the invading species make matters worse?
These are bread-and-butter questions for ecologists and these plants have been studied extensively. Still, answers to these questions commonly start with, "It's unclear" or "It depends...". It depends on which invasive you are talking about and it depends on which ecological community type has been invaded. Asiatic Bittersweet (AB) is present in the forest where ever there is a break in the canopy. It is found along the margins of wetland areas and in successional areas used in the past for agricultural. But what about isolated breaks in the canopy such in the small marsh located near the center of the forest? I have not yet spotted any AB there. That marsh does contain Japanese Barberry, and quite likely other non-native wetland invaders, but why no AB? Is there something about the ecology of the marsh or is it simply that AB had not yet spread to that location?
There are many unknowns around how native communities adapt to species that suddenly appear on the scene. And that is the basis for my assertion that anyone can do important research by capturing data about these communities. The key is the use of methods that preserve the meaning of the data for the long term.
My project is based on an assumption that well established non-native species are part of a new norm for these communities. In other words, we may need to define new communities that incorporate the presence of these species. With that as a starting point I want to know whether newly adapted communities will be more or less resilient in the face of future changes. And these questions go well beyond new plant species appearing in swamps that few people ever see. Ecological changes also alter the mix and behaviors of non-plant species including friendly insects such as ticks and mosquitos. I grew up running and playing and tramping through forests and fields and swamps and ticks were almost never seen. A word of warning that if you visit the Hemlock Forest area, you need to take precautions against the deer ticks (Brown Legged Ticks) that carry Lyme disease. These little critters are very common and very friendly. The paper referenced in this article proposes that greater bio-diversity reduces the spread of parasitic disease and we are reducing biodiversity at a pace and scale that has rarely occurred in the past (the deep past, millions of years).
There are many unknowns around how native communities adapt to species that suddenly appear on the scene. And that is the basis for my assertion that anyone can do important research by capturing data about these communities. The key is the use of methods that preserve the meaning of the data for the long term.
My project is based on an assumption that well established non-native species are part of a new norm for these communities. In other words, we may need to define new communities that incorporate the presence of these species. With that as a starting point I want to know whether newly adapted communities will be more or less resilient in the face of future changes. And these questions go well beyond new plant species appearing in swamps that few people ever see. Ecological changes also alter the mix and behaviors of non-plant species including friendly insects such as ticks and mosquitos. I grew up running and playing and tramping through forests and fields and swamps and ticks were almost never seen. A word of warning that if you visit the Hemlock Forest area, you need to take precautions against the deer ticks (Brown Legged Ticks) that carry Lyme disease. These little critters are very common and very friendly. The paper referenced in this article proposes that greater bio-diversity reduces the spread of parasitic disease and we are reducing biodiversity at a pace and scale that has rarely occurred in the past (the deep past, millions of years).
This post is a lot longer than I had intended but there you have it; the what and why; next up, the how.
References and Resources
Landscape Ecology (Wikipedia)
Study Shows How Biodiversity can Protect Against Disease
References and Resources
Landscape Ecology (Wikipedia)
Study Shows How Biodiversity can Protect Against Disease
