Global study finds predators are most likely to be lost when habitats are converted for human use

A first of its kind, global study on the impacts of human land-use on different groups of animals has found that predators, especially small invertebrates like spiders and ladybirds, are the most likely to be lost when natural habitats are converted to agricultural land or towns and cities. The findings are published in the British Ecological Society journal Functional Ecology.

A Malaysian spider, one of the small predators found in our study to be
most affected by habitat loss [Credit: Tim Newbold]

Small ectotherms (cold blooded animals such as invertebrates, reptiles and amphibians), large endotherms (mammals and birds) and fungivores (animals that eat fungi) were also disproportionally affected, with reductions in abundance of 25-50% compared to natural habitats.

The researchers analysed over one million records of animal abundance at sites ranging from primary forest to intensively managed farmland and cities. The data represented over 25,000 species across 80 countries. Species were grouped by size, whether they were warm or cold blooded and by what they eat. Species ranged from the oribatid mite weighing only 2x10-6g, to an African elephant weighing 3,825kg.

Dr. Tim Newbold at UCL (University College London) and lead author of the research said: "Normally when we think of predators, we think of big animals like lions or tigers. These large predators did not decline as much as we expected with habitat loss, which we think may be because they have already declined because of human actions in the past (such as hunting). We find small predators - such as spiders and ladybirds - to show the biggest declines."

The results indicate that the world's ecosystems are being restructured with disproportionate losses at the highest trophic levels (top of the food chain). Knowing how different animal groups are impacted by changing land-use could help us better understand how these ecosystems function and the consequences of biodiversity change.

"We know that different types of animals play important roles within the environment - for example, predators control populations of other animals. If some types of animals decline a lot when we lose natural habitats, then they will no longer fulfil these important roles." said Dr. Tim Newbold.

The conversion of land to human use is associated with the removal of large amounts of natural plant biomass, usually to give space for livestock and crops. The limiting of the quantity and diversity of resources available at this level potentially explains the disproportionate reductions in predators seen in this study. As you go up the trophic levels (food chain), resource limitations are compounded through a process known as bottom-up resource limitation.

The study is part of the PREDICTS project which explores how biodiversity responds to human pressures. The researchers analysed 1,184,543 records of animal abundance in the PREDICTS database, gathered from 460 published scientific studies. This database included all major terrestrial vertebrate taxa and many invertebrate taxa (25,166 species, 1.8% of described animals).

Species were sorted into functional groups defined by their size, trophic level (what they consumed) and thermal regulation strategy (warm or cold blooded). The type of land-use at each of the 13,676 sample sites was classified from the description of the habitat in the source publication. The six broad categories were primary vegetation, secondary vegetation, plantation forest, cropland, pasture and urban. Three levels of human use intensity were also recorded: minimal, light and intense.

Dr. Tim Newbold explained that studies like this are limited by the available data: "As with all global studies, we are limited in the information that is available to us about where animals are found and what they eat. We were able to get information for more animals than ever before, but this was still only around 1 out of every 100 animals known to science."

The researchers also observed biases in the spread of data across types of land-use, animal groups and parts of the world. "Natural habitats and agricultural areas have been studied more than towns and cities. We think this is because ecologists tend to find these environments more interesting than urban areas as there tend to be more animals in them." said Dr. Tim Newbold. The researchers also found that large parts of Asia were under sampled for several functional groups. Birds were also better represented among vertebrates and insects better represented among invertebrates.

The researchers are now interested in exploring how groups of animals that play particularly important roles for agriculture, such as pollinating or controlling crop pests, are affected by habitat loss.

Author: Davy Falkner | Source: British Ecological Society [January 21, 2020]

Preparing land for palm oil causes most climate damage

New research has found preparing land for palm oil plantations and the growth of young plants causes significantly more damage to the environment, emitting double the amount of greenhouse gases than mature plantations.

Peat swamp deforestation and drainage for new oil palm plantations in North Selangor
Peat Swamp Forest, Malaysia [Credit: Stephanie Evers]

This is the first study to examine the three main greenhouse gas emissions across the different age stages of palm oil plantations. It was carried out by plant scientists from the University of Nottingham in the North Selangor peat swamp forest in Malaysia with support from the Salangor State Forestry Department. It has been published in Nature Communications.

Palm oil is the most consumed and widely traded vegetable oil in the world. Global demand has more than tripled in the last eighteen years, from around 20 million tonnes in 2000 to over 70 million in 2018 and Malaysia is the world's second largest producer. The University of Nottingham researchers analysed five sites at four different stages of land use: secondary forest, recently drained but uncleared forest, cleared and recently planted young oil palm plantation and mature oil palm plantation.

Laboratory analysis of soil and gas from these sites showed that the greatest fluxes of CO2 occurred during the drainage and young oil palm stages with 50% more greenhouse gas emissions than the mature oil palms. These emissions also account for almost a quarter of the total greenhouse emissions for the region.

Tropical peat swamp forests hold around 20% of global peatland carbon. However, the contribution of peat swamp forests to carbon storage is currently under threat from large-scale expansion of drainage-based agriculture including oil palm and pulp wood production on peatlands.

Draining peatlands increases the oxygen levels in the soil, which in turn increases the rate of decomposition of organic material, resulting in high CO2 emissions from drained peatlands. In addition to CO2, peatlands also emit the powerful greenhouse gases (CH4 and N2O8)..

Dr Sofie Sjogersten from the University of Nottingham's School of Biosciences led the research and said: "Tropical peat swamps have historically been avoided by palm oil growers due to the amount of preparation and drainage the land needs, but as land becomes more scarce there has been an increased demand to convert sites and the periphery of North Selangor is being heavily encroached upon by palm oil plantations. Our research shows that this conversion comes at a heavy cost to the environment with greater carbon and greenhouse gas emissions being caused by the early stages of the growth of palm oil."

Source: University of Nottingham [January 21, 2020]

Pyrenees glaciers 'doomed', experts warn

Glaciers nestled in the lofty crags of the Pyrenees mountains separating France and Spain could disappear within 30 years as temperatures rise, upending ecosystems while putting local economies at risk, scientists say.

A view of the Pyrenees from the observatory at the Pic du Midi de Bigorre, where the average temperature
has risen by 1.7 degrees since 1880 [Credit: Pascal Pavani/AFP]

"We can't set a precise date but the Pyrenees glaciers are doomed," Pierre Rene, a glaciologist with the region's Moraine glacier study association, told AFP.

He estimates the end will come by 2050, based on the group's measurements of nine of the 15 glaciers on the French side over the past 18 years.

The United Nations has said the past decade has been the hottest on record and warned that persistent greenhouse gas emissions were expected to push average global temperatures even higher, leading to retreating ice cover, rising sea levels and increasingly extreme weather. It also confirmed that 2019 was the second hottest year on record, after 2016.

Surveys, core samples and GPS tracking of the Pyrenees glaciers all point to the same conclusions already noted at glaciers in the Alps and elsewhere: Warmer and drier winters appear to be inexorably shrinking and thinning the ice fields.

The total surface area of the nine glaciers tracked by Moraine now stands at 79 hectares (195 acres) compared with 140 hectares just 17 years ago, Rene said.

That is just a small fraction of the 450 hectares they covered in the middle of the 19th century—and the pace of decline is accelerating.

Since 2002, the nine glaciers have lost 3.6 hectares every year, the equivalent of five soccer pitches, Moraine says in its report on the 2019 season.

Last year was no exception, with the bottom edge of five glaciers tracked by Moraine retreating by 8.1 metres (27 feet) on average last summer, up from 7.9 metres recorded in previous years, it said.

'Wiped off the map'

Scientists also warn of the hit to high-altitude ecosystems and biodiversity, with consequences that will ripple well beyond the mountainous zones.

Glaciers and the cold rivers they feed harbour bacteria and fungi that have adapted to the harsh conditions, including the near-absence of light, said Sophie Cauvy-Fraunie, a researcher at the INRAE agricultural and environmental institute.

Microscopic algae also provides a first link in the food chain of glacier environments, sustaining glacial fleas and other insects.

As temperatures rise and more ground is exposed as the glaciers retreat, the landscape will become vulnerable to colonisation from plants and animals that currently can survive only at lower altitudes.

"If native species in the Pyrenees depend on glacial influences, you can imagine that they are going to be wiped off the map," Cauvy-Fraunie said.

The regional OPCC climate observatory estimated in a 2018 report that average maximum temperatures across the Pyrenees could rise by 1.4 to 3.3 degrees Celsius (2.5 to 4 Fahrenheit) by the middle of this century.

The increase has been even more dramatic at higher altitudes, where shrinking glaciers are seen as a harbinger of dire consequences across the range.

On the 2,870-metre (9,416-foot) Midi de Bigorre peak above the La Mongie ski resort—favoured by French President Emmanuel Macron—the average temperature has risen by 1.7 degrees since 1880, compared with a global average of 0.85 degrees, Moraine says.

Tourism affected

That could spell disaster for the roughly three dozen ski resorts on both the French and Spanish sides, as well as the popular stations in Andorra.

Already this year, around half of French resorts had to push back their scheduled openings before the Christmas holidays because of warm winds sweeping up from the south.

That came after a 2018-2019 season that saw the lowest snowfalls since regular measurements began 22 years earlier, according to the Meteo France weather service.

It took a heavy toll on tourism as lift ticket sales and hotel reservations plunged, with many skiers heading to higher slopes in the French Alps.

Already several glaciers have been reduced to little more than year-round snow packs, which will also impact the summer tourist season.

Rene said climbers will lose their "stepladders" for ascents to the highest peaks, "making their routes to the top more difficult".

And for hikers at lower elevations, the retreat will destabilise the newly exposed slopes, heightening the risk of rock falls or even avalanches.

Author: Herve Gavard | Source: AFP [January 20, 2020]