Habitat loss is bad news for species – especially for top predators

Scientists at Linkoping University, Sweden, have simulated what happens in ecosystems when the habitats of different species disappear. When plants and animals lose their habitats, predator species at the top of the food chain die out first. The results have been published in Ecology Letters, and may provide information for and strengthen initiatives to preserve biodiversity.

Credit: Nagel Photography/Shutterstock

One of the most serious threats against biodiversity is habitat loss. Humans cause severe changes in the landscapes when converting or removing natural land to be used for construction or food production. In addition, climate change is also causing some regions to become uninhabitable for some species. Researchers at Linkoping University have developed a mathematical method to investigate how large ecosystems are affected when habitat disappears.

"We can reach two important conclusions from our study. The first is that initiatives to preserve biological diversity must preserve habitat and not only focus on a particular species. It is very important to consider the interactions between the ecosystem's species by looking at the food web—which animals and plants are eaten by which other animals. The second conclusion is that the order in which habitats disappear has a profound significance," says Anna Eklof, senior lecturer in the Department of Physics, Chemistry and Biology (IFM) at Linkoping University.

The LiU researchers use modeling and computer simulations to study ecological networks, which describe how the various species in an ecosystem interact. The article, published in Ecology Letters, combines two mathematical models: a classical and a new one. The model described in the article distinguishes between suitable habitats in which species can live, and other areas in which they cannot. Suitable habitat patches are distributed across the landscape, with different plant and animal species spread across them. The species are connected to each other in a food web, a network that describes how they feed on each other. A hare eats several types of plants, the hare and several other prey species can become food for foxes, and the fox is one of the predators at the top of the food web.

The survival of an animal in a particular habitat depends on having the correct prey animals or plants in the same habitat patch. The model developed by the researchers also considers how effectively species can move between the habitat patches. In the real world, the habitat patches are often separated by inhospitable regions, such as a road with heavy traffic, that can prevent plants and animals from moving between them. If dispersal between different habitat patches becomes more difficult, probability increases that a species becomes extinct in the ecological network—which in turn influences the survival of other species.

 

The researchers have used the model to analyze a large number of simulated networks involving several hundreds of species. They also tested the model on a dataset of measurements describing the food web of the Serengeti National Park in Tanzania. In order to investigate how ecosystems are affected by habitat loss, the researchers ranked the habitat patches in order of how important they are for species at the bottom of the food chain. They then simulated three different ways in which habitat loss can occur: with the least important habitat patches removed first, the most important ones first, or removing them in a random order. The destruction of habitat in a random order is similar to what happens when humans construct roads or buildings without considering how valuable the region is for different species.

"In our model, the species at the upper levels of the food chain die out first when habitat patches are lost. What surprised us was that the damage to the ecosystem was almost the same when patches were lost in a random order as when the most valuable patches were lost first," says research fellow Gyorgy Barabas.

The researchers emphasize that it is important to classify how significant various habitats patches are when considering initiatives to preserve ecosystems, and to give priority to the most valuable ones. The resilience of the ecosystem to species extinctions can also be improved by, for example, strengthening connections between patches. By taking such matters into consideration when determining how land is used, humans can protect ecosystems and prevent species from becoming extinct—particularly species that are high up in the food chain.

Author: Karin Soderlund Leifler | Source: Linkoping University [October 28, 2020]

Support The Archaeology News Network with a small donation!

Hidden losses deep in the Amazon rainforest

Few places on Earth are as rich in biodiversity and removed from human influence as the world's largest rainforest -- the Amazon. Scientists at Louisiana State University (LSU) have been conducting research within the pristine rainforest for decades. However, they began to notice that some of the animals, specifically birds that forage on and near the forest floor, had become very difficult to find.

New research shows animal patterns are changing in the absence of landscape change, which signals
a sobering warning that simply preserving forests will not maintain rainforest biodiversity
[Credit: Vitek Jirinec, LSU]

"What we think is happening is an erosion of biodiversity, a loss of some of the richness in a place where we would hope biodiversity can be maintained," said LSU School of Renewable Natural Resources Professor Philip Stouffer, who is the lead author of a new study published in Ecology Letters.

Stouffer began leading field research deep within the Amazon rainforest, north of Manaus, Brazil, when he was a post-doctoral researcher with the Smithsonian in 1991. With support from the National Science Foundation, he continued to oversee bird monitoring at the Biological Dynamics of Forest Fragments Project until 2016. However, around 2008, he and his graduate students noticed that they could seldom find some bird species that they had observed in previous years.

Stouffer and his students devised a research plan to collect new data that would be directly comparable to historical samples from the early 1980s. LSU graduate students Vitek Jirinec and Cameron Rutt collaborated with Stouffer to synthesize the results, aided by the computational modeling expertise from co-author LSU Department of Oceanography & Coastal Sciences Assistant Professor Stephen Midway. The team analyzed the vast dataset that spanned more than 35 years and covered 55 sites to investigate what Stouffer and his graduate students had observed in the field.

"It's a very robust dataset from a variety of places collected over many years. It's not just some fluke. It looks like there's a real pattern and it looks like it could be linked to things we know are happening with global climate change that are affecting even this pristine place," Midway said.

This downward trend signals a shifting baseline that could have gone undetected.

"Our nostalgia was correct--certain birds are much less common than they used to be," Stouffer said. "If animal patterns are changing in the absence of landscape change, it signals a sobering warning that simply preserving forests will not maintain rainforest biodiversity."

Winners and losers

In general, the birds that have experienced the most dramatic declines live on or near the forest floor where they forage on arthropods, mostly insects. However, there is some variation among species winners and losers in the rainforest.

The iconic voice of the Amazon rainforest, the Musician Wren, is one of the birds that researchers
have discovered is on the decline in pristine, remote parts of the Amazon
[Credit: Philip Stouffer, LSU]

For example, the Wing-banded Antbird , or Myrmornis torquata, is one of the species that has declined since the 1980s. It is also one of the species that forages insects on the forest floor by searching under leaves and other debris. Also declining is the Musician Wren , or Cyphorinus arada, a seldom-seen bird with one of the iconic voices of the Amazon.

Conversely, the White-plumed Antbird , or Pithys albifrons, has not declined and remains common. Its foraging strategy may be the key to its resilience. The White-plumed Antbird follows swarms of marauding ants that churn up other insects hidden on the forest floor. The antbird jockeys for an advantageous position ahead of the ant swarm and preys upon the fleeing insects. The White-plumed Antbird is not tied to one location in the rainforest. It travels and eats a variety of prey surfaced by the swarms of ants.

The scientists also found that frugivores, or birds that also eat fruit, are increasing in abundance. This suggests that omnivorous birds with more flexible diets can adjust to changing environmental conditions.

More research is needed to better understand the hidden losses and shifting baseline that are happening in the Amazon rainforest and other parts of the planet. "The idea that things are changing, even in the most pristine parts of our planet yet we don't even know it, illustrates the need for us to pay more attention," Stouffer said.

Source: Louisiana State University [October 26, 2020]

Support The Archaeology News Network with a small donation!