"Expect the unexpected and be ready for surprises”
September 20, 2016
Tropical forests once covered most of Puerto Rico, providing a network of ecosystems rich in biological diversity.
But by the early 1940s, almost 97 percent of those forests had been slashed and burned, cleared for agriculture and livestock.
Agricultural production on much of that land has since ceased, and forests are growing back. More than half of the island has undergone reforestation, most of it through natural regeneration.
But the new forests are unlike those they’ve replaced.
“We’re looking at landscapes with secondary forests that are regrowing after different types of land uses, and we’re finding that they grow back a lot quicker than we expected. But the species composition can be really different from what we think was there before,” says Erika Marín-Spiotta, an associate professor of geography and Nelson Institute affiliate.
Marín-Spiotta is studying how a variety of human-driven factors, including changes in soil composition and competition from non-native species, can lead to combinations of plants not seen before – what ecologists call “novel ecosystems.”
Left: A deforested hillslope, once common across Puerto Rico. Center: A 60-year-old secondary forest rises behind recently active pasture. Right: Secondary forests restore ecological function, but with combinations of species often different from native forests. Photos by Erika Marín-Spiotta.
THE RISE OF NOVELTY
Novel ecosystems are becoming increasingly common in the Anthropocene (a new proposed geologic epoch reflecting the dominant influence of humans across the globe), developing in response to unprecedented change.
Take the southwestern deserts of the United States. Future climatic conditions are likely to be much different than they are today.
“The predicted newer, higher temperatures are outside the range in which species have evolved,” explains Anna Pidgeon, a UW-Madison associate professor of forest and wildlife ecology who studies conservation challenges posed by human impacts on wildlife habitat. “Even a relatively small increase in absolute temperature can mean drastic changes for species’ ability to cope.”
lock-step when environments
change. You see a reshuffling
of species into what we call
no-analogue ecosystems –
they’re different from anything
we’ve seen in the past.”
Large-magnitude changes force some species out and create opportunities for others, a fact seen in every kind of landscape, including cities.
“The novelty of the urban ecosystem is that there’s a high abundance of food and access to free water, meaning a few species can exist at really high abundances relative to what they could elsewhere,” says Pidgeon. “So we get communities of birds, for instance, completely different from what was naturally here.”
As a result, says Pidgeon, the fields of wildlife management, conservation and restoration are becoming increasingly complicated as novel ecosystems develop in response to conditions that have no comparisons in the historical record.
LOOKING TO FOSSILS
To understand the ecosystems of today – and tomorrow – researchers like Jack Williams, a professor of geography and director of the Nelson Institute Center for Climatic Research (CCR), look to paleoecology, the study of past ecosystems.
Using geological data such as fossils, paleoecologists combine geology, geography, ecology and climatology to answer the most pressing ecological questions.
How fast did the climate change in the past? How did species and ecosystems respond? What should we do in the face of massive ecological uncertainty today?
Species unable to move quickly enough to stay ahead
of change may need assisted migration, some suggest.
In the Anthropocene, few ecosystems will be left untouched by rapid change, and the fossil record shows that nature’s responses can vary widely.
“Species don’t march in lock-step when environments change,” says Williams. “You see a reshuffling of species into what we call no-analogue ecosystems – they’re different from anything we’ve seen in the past.”
Still, scientists have documented some consistent patterns. For example, when the climate changes, species move.
“Migration and range shift is a first-order response to climate change, and these range shifts can be surprisingly fast. With rapid warming in a short amount of time, you see plant communities completely turn over in a period of 10 to 20 years,” says Williams.
In other words, species will have to move to survive on a rapidly warming planet. Williams suggests that we might have to assist the migration of plants and animals that can’t move quickly enough to stay ahead of change.
“We should be ready to pursue assisted migration for species that are poor dispersers and are at low risk of causing damage in their new habitats,” says Williams. “In the face of uncertainty, we should conduct multiple and long-term management and conservation experiments, because we don’t necessarily know which approaches will best conserve biodiversity and ecosystem services in the decades to come.”
RESTORATION OF SERVICES
Restoring and maintaining ecosystem services is a key consideration for ecologists trying to find the best way forward. In those regrowing forests in Puerto Rico, for example, non-native species have become established and are there to stay, forcing scientists to weigh ideal outcomes against pragmatic approaches.
“In many parts of the world, people are totally against exotic or non-native species, but sometimes native species have a really hard time growing back,” explains Marín-Spiotta.
and our minds open, and then
realize that we’re not ever
going to be able to prepare
for everything."
Marín-Spiotta and her colleagues are trying to understand what factors influence whether native forests are able to grow back, and how quickly. In the deforested lands she’s studying, non-native trees can help shade out persistent grasses that have become established in abandoned farmlands and pastures. (In some cases, that can help many of the original native species eventually grow back.)
A major goal, she says, is to restore wildlife habitat, soil stability and other ecosystem
services that a healthy forest provides.
“Biomass recovers very quickly, but often with very different species composition. Does that matter?” Marín-Spiotta asks.“Does that influence nutrient cycles? Does that influence hydrology? Does a forest dominated by non-native species provide the same function or ecosystem services as another forest?”
Those are the kinds of questions ecologists must answer in the Anthropocene.
CREATIVITY, RESILIENCE AND HOPE
Confronted with this no-analogue future, scientists are being forced to throw conventional approaches out the window.
“We are going off the map,” says Williams. “Novel climates pose a challenge to ecological forecasting, because they force us to predict species responses to climates that we haven’t observed. We should expect the unexpected and be ready for surprises.”
For Pidgeon, this sometimes means accepting change.
Novel climates pose a challenge to ecological forecasting;
for example in Wisconsin, the distribution of plant
species is shifting northwest. Photo: Wisconsin DNR
“It’s a big, thorny question to wrestle with,” Pidgeon says. “What’s the baseline or reference point that you’re trying to manage towards? At what point do you recognize the contributions of the novel ecosystem?”
She says we also need to target resources where we can make a difference, and know where we can’t. In Wisconsin, for example, that might mean aligning conservation efforts with the rise in temperatures and precipitation projected by CCR scientists.
“Thinking from a management point-of-view, you probably don’t want to manage for species that are going to do poorly in a warmer, wetter world,” says Pidgeon. ”You want to think about which battles to pick based on our best understanding of how things are going to change.”
The rate and scale of anthropogenic changes can be daunting, and Wisconsin ecologists are wrestling with what this all means for science and management. Still, some see reasons for hope.
“Species have survived multiple glacial and inter-glacial cycles and can adapt to global warming,” says Williams. “We have a lot of ecological knowledge about this. I’m optimistic that we will figure it out over the next 30 to 40 years, but it becomes a race between how fast the climate system is going to change, how much carbon we put into the atmosphere, and how quickly we figure out the technological solutions and social buy-in to fix the problem.”
Marín-Spiotta agrees on the need to be light on our feet.
“We have to keep our options and our minds open,” she says,“and then realize that we’re not ever going to be able to prepare for everything, because there’s a lot we don’t know.”
BRACE FOR IMPACT: PROTECTING THE RIGHTS OF CLIMATE CHANGE VICTIMS
The impoverished village of Kivalina, Alaska, located on a fragile island above the Arctic Circle, perfectly illustrates the intersection of climate change and human rights.
Record-high ocean temperatures have caused the sea ice that surrounds this low-lying island to thin. With sea levels rising and its protective ice melting, the island is eroding at an alarming rate. Experts predict Kivalina will be completely submerged in ten years.
“When an entire community has to move due to climate change, what rights do its citizens have?” asks Sumudu Atapattu, a University of Wisconsin Law School senior lecturer and faculty affiliate of the Nelson Institute. “Do they get to decide where and when they go? Does the new place have access to basic resources?”
With sea levels rising and its protective ice melting,
experts predict that Kivalina Island will be completely
submerged in ten years. Photo credit ShoreZone.
Her questions are rhetorical: according to Atapattu, the U.S. is legally bound to help relocate Kivalina residents to a safer place, and in doing so, it must employ a broad human rights framework. But so far, the funds necessary for relocation haven’t been allocated, and there’s no government mechanism in place to assist in a move.
Last October, Atapattu published Human Rights Approaches to Climate Change: Challenges and Opportunities. The book looks to international law for answers to hard questions about mitigating climate change and preparing people for its impacts.
Atapattu has long argued that climate change threatens fundamental human rights, such as the right to clean water and healthy food, the right to a safe place to live, even the right to life itself — and that the world’s poor are hardest hit.
“We’re talking about millions who are in immediate danger, or who will eventually be displaced, by rising sea levels, extreme weather events or resource scarcity,” she says. “We have a duty to protect their rights.”
Atapattu attended a portion of the historic United Nations Conference on Climate Change in Paris last year, when 195 countries adopted a landmark global climate deal. One of the main developments was the shared commitment to limit warming to no more than 2 degrees Celsius above preindustrial levels, with a longer-term goal of holding temperature increases to less than 1.5 degrees – a matter of survival for some countries, Atapattu says.
“If we can’t stop sea levels from rising, we can expect a huge humanitarian catastrophe with regard to low-lying small island states,” she says. “Their citizens stand to lose everything, including the land their families have lived on for generations. That is in spite of their minimal contribution to the problem.”
-Tammy Kempfert