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Study reveals exactly what happens to nature when forests are cut down

Around 12,000 years ago, the first humans began their journey into agriculture. In the regions we now identify as Iraq and Syria, nestled between the Euphrates and Tigris rivers, small collectives of people embarked on the cultivation of peas, lentils, and barley. Each group operated independently, making their own discoveries and innovations along the way.

In order to create room for these fledgling fields and the animals they kept, they had to cut down trees. It was the beginning of a human-initiated transformation of nature, bending and shaping it to meet our own needs.

Our ancestors were aware of the consequences of their actions. They knew that once the forests were cleared and the fields set up, certain species of animals and plants would cease to exist in those regions. In our current era, we understand that modern, high-intensity agriculture poses one of the greatest threats to global biodiversity.

Despite this knowledge, there remains a gap in our understanding. Specifically, we lack concrete information about the direct impact on the ecosystem – on its plants, insects, and animals – when a forest is cleared, and the land is tilled and sowed.

In response to this, Gabor Lovei from the Department of Agroecology at Aarhus University and a group of Portuguese colleagues embarked on a research journey. They chose the island of Terceira in the Azores as their laboratory, an ideal location due to the preservation of some of its original forest.

Gabor Lovei, however, was taken aback by the results of the study. “The changes in the ecosystem were less extensive than I’d imagined. True enough, there were fewer large and small animals in the fields, but on a number of other parameters, activity in the ecosystem had actually increased,” said Lovei.

The unique nature in the Azores

The Azores had largely remained untouched until 1427. The islands were lush and thriving in the middle of the Atlantic, hosting deep-green trees and a variety of plants. This rich biodiversity was due to the islands’ unique combination of high heat, frequent precipitation, and volcanic soil.

That all changed in the 15th century when Portuguese sailors stumbled upon the forested mountains in the middle of the Atlantic. Smallholders, disillusioned with the royal favours directed towards manor houses in Portugal, packed up their tools and set sail for the Azores. They felled the forests and planted wheat and other crops.

Their efforts bore fruit. The yields were significantly higher than on the mainland, and soon, the news spread. Farmers flocked to the Azores, resulting in rapid deforestation and transformation into agricultural land. The only areas spared were those where the terrain was too mountainous or the soil too difficult to cultivate.

It was in these untouched parts of the original forest that Gabor Lovei carried out his research. “In Denmark – and most other places in Europe – the forest is not original. It has been felled, replanted and changed by humans for thousands of years. In the Azores, on the other hand, there is completely original forest – and it’s gold for this type of research,” said Lovei.

Innovative trick used in this study

When scientists want to study the impact of agriculture on various species, they often don their hiking boots and embark on a field journey. They systematically comb through fields, meadows, and forest edges, meticulously recording their findings at different times of the day and on multiple occasions. 

However, these traditional methods primarily shed light on animal populations, not the whole ecosystem’s response to agricultural changes.

Gabor Lovei, a researcher, had a different approach. He aimed to investigate the entire ecosystem’s reaction to forest felling and the establishment of fields, so he had to employ innovative methods.

Lovei began his investigation by planting several mature lettuces in three different environments: an original forest, cultivated fields, and cow grazing fields. He left the plants undisturbed for two weeks. After this period, he assessed the area covered by the lettuce and the amount consumed, providing a measure of the plant-eating activity in each ecosystem.

He replicated this process with larvae to assess predation levels. The more larvae consumed, the more wildlife – birds, rodents, frogs – were likely present in the area. Lovei also scattered small boxes of seeds to observe how many would disappear. He even buried teabags ten centimeters deep into the soil to examine the microorganisms’ activity levels, which break down organic matter.

Additionally, he planted strawberries to gain insights into pollination across the different areas. All these mini-experiments collectively painted a picture of the ecosystem-wide changes occurring when forests are felled and fields established.

Researchers find fewer animals in the fields

Among all parameters Lovei studied, insect predation showed the greatest difference. He found that significantly more larvae disappeared in the forest than in the cultivated field and grazing areas.

According to Lovei, this suggests more wildlife inhabits the forest. “Larvae are typically eaten by rodents, birds, and lizards. Our findings suggest that there were significantly more of them in the forest, because more larvae disappeared between the trees,” said Lovei.

Seeds also vanished more rapidly in the forest, which Lovei attributes to the higher humidity levels fostering a wider range of invertebrates. “Animals like snails and beetles, which eat seeds, can live there.”

However, he found no difference regarding pollination and the number of soil microorganisms. Interestingly, plant pollination was slightly higher on maize fields than in the forest. But Lovei cautions against seeing this as an indication of greater bee diversity. He clarified that cultivated fields usually have few plant types, meaning that “the same few bee species are responsible for pollination.”

What farmers can do to help

Deforestation by local farmers inevitably leads to a loss of biodiversity, a fact clearly demonstrated through Gabor Lovei’s extensive research. But does his work also reveal ways to regain some of that lost biodiversity in our agricultural fields?

The answer, Lovei assures us, is yes. His results offer a fresh understanding of which parts of the ecosystem are most impacted by farming practices.

Lovei has observed that “snails and beetles have a hard time on the fields.” To rectify this, he suggests that farmers could leave small pockets of natural vegetation untouched in their fields. For instance, allowing roots from dead trees to decompose naturally could attract many types of beetles.

Another issue stems from the unintentional introduction of non-native species during farming, which can disrupt the natural ecosystem. In the Azores, rats became invasive and displaced a large portion of the local fauna.

“By making space for small pockets of non-cultivated nature in and around the fields, we know that the native species will survive more easily. They’re simply more resistant to invading species,” explained Lovei.

Is it possible, then, to apply these findings to a place like Denmark, which has distinct natural conditions? The Azores’ nature is quite different: Denmark is colder, its soil is different, and virtually no original nature remains.

Despite these differences, Lovei believes the results from the Azores can still apply to Danish conditions. “Such comprehensive experiments have never been conducted on the European mainland, but some of the parameters have been studied in other European countries. The pattern was roughly the same. Therefore, we can assume that Danish nature reacts more or less in the same way to deforestation and cultivation.”

He is quick to remind us, though, that agriculture isn’t the sole threat to biodiversity. Urban environments, including our own backyards, also impose limitations on animal habitats. He emphasizes, “That’s why it’s important to do something in our own backyard.”

Planting native species can make a significant difference, Lovei suggests. Cultivating trees and flowers indigenous to Denmark, rather than exotic plants, can greatly benefit the local ecosystem. “Stop mowing the lawn. This will make a huge difference for many species.”

This research, while highlighting the detrimental effects of farming practices on biodiversity, also points to viable strategies for mitigating these impacts. The findings serve as a call to action for both farmers and individuals, reminding us of our shared responsibility in preserving our planet’s precious biodiversity.

More about deforestation

Deforestation is the process of clearing, thinning, or eliminating forested areas, often to make way for agriculture, logging, or urban development. It has profound impacts on the Earth’s ecosystems and the overall environment, affecting biodiversity, climate, and human societies.

Loss of Biodiversity

Forests are home to a majority of the world’s terrestrial biodiversity. They house millions of species of plants, animals, fungi, and microorganisms, many of which are still undiscovered. When forests are cleared, these species lose their habitats, leading to population declines and extinctions. This loss of biodiversity can disrupt ecosystems and diminish their resilience, potentially leading to the collapse of entire food webs.

Climate Change

Forests play a crucial role in regulating the Earth’s climate. They act as “carbon sinks,” absorbing carbon dioxide from the atmosphere and storing it in plant tissues and soils. When forests are cut down and burned or allowed to decompose, this stored carbon is released back into the atmosphere, contributing to global warming. Deforestation is estimated to be responsible for about 10-15% of the world’s greenhouse gas emissions.

Disruption of the Water Cycle

Trees and plants in forests contribute significantly to the water cycle. They release water vapor into the atmosphere through transpiration, promoting the formation of clouds and precipitation. When forests are removed, this process is disrupted, potentially leading to changes in rainfall patterns and an increased risk of drought.

Soil Erosion and Degradation

Forests help to protect soil from erosion by reducing the impact of rain and wind. They also contribute to soil fertility through the recycling of nutrients. Without trees, soils are more vulnerable to erosion, and their fertility can decline over time, making the land less suitable for agriculture and other uses.

Impact on Indigenous Communities

Many indigenous and local communities depend on forests for their livelihoods, food, water, and cultural practices. Deforestation can lead to the displacement of these communities and the loss of their traditional knowledge and ways of life.

In short, deforestation has far-reaching impacts on the Earth’s ecosystems and the environment. Addressing this issue is vital for biodiversity conservation, climate change mitigation, and sustainable development.

Image Credit: Jules Verne Times Two / Creative Commons


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