Écologie, extinctions…

1. Mégafaune et biomasse aujourd’hui
Déclin des insectes et petits animaux aujourd’hui
Extinctions et déclins de mégafaune depuis le pliocène
Impact de la chasse aux trophées
Sujets d’écologie divers

Mégafaune et biomasse aujourd’hui

Are we eating the world’s megafauna to extinction?
Ripple et al.
Conservation letters, 2019

Surprisingly, direct harvesting of megafauna for human consumption of meat or body parts is the largest individual threat to each of the classes examined, and a threat for 98% (159/162) of threatened species with threat data available. Therefore, minimizing the direct killing of the world’s largest vertebrates is a priority conservation strategy that might save many of these iconic species and the functions and services they provide.

The biomass distribution on Earth
Bar-On et al.
PNAS 2018

Biomass distribution current

A continent-wide assessment of the form and intensity of large mammal herbivory in Africa
Hempson et al.
Science, 2015

Hempson 2015 biomass to rainfall

Defaunation in the Anthropocene
Rodolfo Dirzo et al.

Among terrestrial vertebrates 322 species have become extinct since 1500, while populations of the remaining species show 25% average decline in abundance. Invertebrate patterns are equally dire:67% of monitored populations show 45% mean abundance decline. Suchanimal declineswill cascade onto ecosystem functioning and human well-being. Much remains unknown about this “Anthropocenedefaunation”; these knowledge gaps hinder our capacity to predict and limit defaunation impacts. Clearly, however, defaunation is both a pervasive component of the planet’s sixth mass extinction, and also a major driver of global ecological change.

Harvesting the Biosphere: The Human Impact
Vaclav Smil
Population and development review, 2011

Smill 2011 biomass evolution

Impacts of Biodiversity Loss on Ocean Ecosystem Services
Worm et al.
Science, 2006

Worm et al. 2006


Déclin des insectes et petits animaux aujourd’hui


Arthropod decline in grasslands and forests is associated with landscape-level drivers
Seibold et al.
Nature, 2019

In annually sampled grasslands, biomass, abundance and number of species declined by 67%, 78% and 34%, respectively. The decline was consistent across trophic levels and mainly affected rare species; its magnitude was independent of local land-use intensity. However, sites embedded in landscapes with a higher cover of agricultural land showed a stronger temporal decline. In 30 forest sites with annual inventories, biomass and species number—but not abundance—decreased by 41% and 36%, respectively. This was supported by analyses of all forest sites sampled in three-year intervals. The decline affected rare and abundant species, and trends differed across trophic levels. Our results show that there are widespread declines in arthropod biomass, abundance and the number of species across trophic levels. Arthropod declines in forests demonstrate that loss is not restricted to open habitats. Our results suggest that major drivers of arthropod decline act at larger spatial scales, and are (at least for grasslands) associated with agriculture at the landscape level. This implies that policies need to address the landscape scale to mitigate the negative effects of land-use practices.

Cette publication lie le déclin des coléoptères dans des zones préservées de l’activité humaine du New Hampshire au réchauffement climatique.

Decline in beetle abundance and diversity in an intact temperate forest linked to climate warming
Jennifer E. Harris et al.
Biological conservation, 2019

Beetle capture rate was least when and where climate was warmest. Capture rate was significantly lower in the 2010s when mean daily temperature was about 1.8 °C warmer, and sampling during 2016–2017 at low, mid and high elevations (320, 540, and 810 m asl, respectively) revealed lowest beetle captures at low elevation where climate was warmest. Most importantly, beetle capture rate was significantly lower after winters with less snow cover during the previous winter, indicating that snow cover in northern hardwood forest is essential for sustaining the beetle community. These results imply that additional climate warming might further reduce the abundance and diversity of beetles and other arthropods inhabiting the forest-floor, potentially affecting critical ecosystem processes such as decomposition and carbon storage.

Decline of the North American avifauna*
Rosenberg et al.
Science, 2019

Using multiple and independent monitoring networks, we report population losses across much of the North American avifauna over 48 years, including once common species and from most biomes. Integration of range-wide population trajectories and size estimates indicates a net loss approaching 3 billion birds, or 29% of 1970 abundance. A continent-wide weather radar network also reveals a similarly steep decline in biomass passage of migrating birds over a recent 10-year period.

Declines in insect abundance and diversity : We know enough to act now
Forister et al.
Conservation science and practice, 2019

Recent regional reports and trends in biomonitoring suggest that insects areexperiencing a multicontinental crisis that is apparent as reductions in abundance,diversity, and biomass. Given the centrality of insects to terrestrial ecosystems andthe food chain that supports humans, the importance of addressing these declinescannot be overstated. The scientific community has understandably been focusedon establishing the breadth and depth of the phenomenon and on documenting fac-tors causing insect declines. In parallel with ongoing research, it is now time forthe development of a policy consensus that will allow for a swift societal response.We point out that this response need not wait for full resolution of the many physi-ological, behavioral, and demographic aspects of declining insect populations. Tothese ends, we suggest primary policy goals summarized at scales from nations tofarms to homes.

No Simple Answers for Insect Conservation: Media hype has missed the biggest concern that ecologists and entomologists have about six-legged life: how little we know about it
Manu E. Saunders
American Scientist, 2019

Widespread, consistent insect declines are a real concern. Yet there is little published evidence that worldwide decline of all insects is happening. The aforementioned studies were localized and skewed toward particular taxa. The authors of the Krefeld and Luquillo studies tried not to overextend their results in their journal articles, but the press releases from the lead authors’ institutions, media coverage, and the recent review paper were less cautious. Sanchez-Bayo and Wyckhuys claimed that their review showed that « almost half of the [world’s insect] species are rapidly declining. » Yet their data show declines for only about 2,900 species–a tiny fraction of the estimated 5 million insect species on Earth.
The Krefeld study is based on trap samples from 63 nature reserve sites in Germany, collected over a 27-year period. But more than half the sites were only surveyed once during the study period, and only 26 sites were surveyed in multiple, though not consecutive, years. The lack of repeated sampling at exactly the same locations over a long period of time limits understanding of the true extent of declines across Europe, let alone in the rest of the world. Moreover, biomass is a poor proxy for abundance or species richness.


Worldwide decline of the entomofauna: A review of its drivers
Sanchez-Bayo & Wyckhuys

Biological conservation, 2019

The main drivers of species declines appear to be in order of importance: i) habitat loss and conversion to intensive agriculture and urbanisation; ii) pollution, mainly that by synthetic pesticides and fertilisers; iii) biological factors, including pathogens and introduced species; and iv) climate change. The latter factor is particularly important in tropical regions, but only affects a minority of species in colder climes and mountain settings of temperate zones. A rethinking of current agricultural practices, in particular a serious reduction in pesticide usage and its substitution with more sustainable, ecologically-based practices, is urgently needed to slow or reverse current trends, allow the recovery of declining insect populations and safeguard the vital ecosystem services they provide. In addition, effective remediation technologies should be applied to clean polluted waters in both agricultural and urban environments.

Climate-driven declines in arthropod abundance restructure a rainforest food Bradford C. Lister & Andres Garcia
PNAS, 2018

Analysis of long-term data on canopy arthro-pods and walking sticks taken as part of the Luquillo Long-TermEcological Research program revealed sustained declines in abun-dance over two decades, as well as negative regressions of abun-dance on mean maximum temperatures. We also document paralleldecreases in Luquillo’s insectivorous lizards, frogs, and birds. While ElNiño/Southern Oscillation influences the abundance of forest arthro-pods, climate warming is the major driver of reductions in arthropodabundance, indirectly precipitating a bottom-up trophic cascade andconsequent collapse of the forest food web.

Une réponse à l’article :

Populations are not declining and food webs are not collapsing at the Luquillo Experimental Forest
Willig et al.
PNAS, 2019

Canopy arthropod density does not decline between 1994 and 2009 but does increase significantly with increasing temperature (figures 5 and 6 of Supplementary Materials), even for the 10 most abundant taxa (tables 1 and 2 of Supplementary Materials), which Lister and Garcia claimed to have used (3).

Long-term data do not suggest a simple decline in adult frogs from 1987 to 2017 (figure 7 of Supplementary Materials) but do document an increase in numbers with increasing temperature (figure 8 of Supplementary Materials). Numbers vary in a consistent and nondirectional manner, except for short-term increases after Hurricanes Hugo and Georges, which modified habitat structure

Et une réponse à la réponse :

Reply to Willig et al.: Long-term population trends in the Luquillo Rainforest
Brad Lister and Andres Garcia
PNAS, 2019

The impact of free-ranging domestic cats on wildlife of the United States
Loss et al.
Nature communication, 2013.

We estimate that free-ranging domestic cats kill 1.3–4.0 billion birds and 6.3–22.3 billion mammals annually. Un-owned cats, as opposed to owned pets, cause the majority of this mortality. Our findings suggest that free-ranging cats cause substantially greater wildlife mortality than previously thought and are likely the single greatest source of anthropogenic mortality for US birds and mammals.


Extinctions et déclins de mégafaune depuis le pliocène

La section commençant à devenir très volumineuse, elle a gagné une page dédiée.


Impact de la chasse aux trophées

Local perceptions of trophy hunting on communal lands in Namibia
Angula et al.
Biological conservation, 2018

Our results suggest that in Namibia, a trophy hunting ban would be viewed very poorly by conservancy residents, and would seriously weaken their support for wildlife conservation. The imposition of trophy hunting policies by countries far from where rural land managers are conserving wildlife would not only restrict communities’ livelihood options, but may have perverse, negative impacts on wildlife conservation.

Banning Trophy Hunting Will Exacerbate Biodiversity Loss
Di Mimin et al.
Trends in ecology and evolution, 2016

International pressure to ban trophy hunting is increasing. However, we argue that trophy hunting can be an important conservation tool, provided it can be done in a controlled manner to benefit biodiversity conservation and local people. Where political and governance structures are adequate, trophy hunting can help address the ongoing loss of species.

Une réponse :
Does Trophy Hunting Support Biodiversity? A Response to Di Minin
et al.
Ripple et al.
Trends in ecology and evolution, 2016

Di Minin et al. [1] are correct in stating that trophy hunting can increase funding for conservation (this is well known), but they have failed to address the effects of trophy hunting on the suite of mechanisms driving species interactions, plant community dynamics, natural selection, trophic cascades, and ecosystem structure and function. While there are many issues relating to the pros and cons of trophy hunting, we suggest that the ecological and evolutionary discussion should focus on relevant variables and interactions that can be linked to trophy hunting.

Une réponse à la réponse :

Trophy Hunting Does and Will Support Biodiversity: A Reply to Ripple et al.
Mimin et al.
Trends in ecology and evolution, 2016

Conservation or the Moral High Ground: Siding with Bentham or Kant
MacDonald et al.
Conservation letters, 2016


Sujets d’écologie divers


Global distribution of earthworm diversity
Philipps et al.
Science, 2019

Vers de terre dans le monde biomasse

Wild pollinator activity negatively related to honey bee colony densities in urban context
Ropars et al.
PLOS One, 2019

Here, we show that in the city of Paris (France), wild pollinator visitation rates are negatively correlated to honey bee colony densities present in the surrounding landscape

Global drivers of population density in terrestrial vertebrates
Santini et al.
Global ecology and biogeography, 2018

Traits determine most of the variation in population density across species,whereas environmental conditions explain the intraspecific variation across populations. Speciestraits, resource availability and climatic stability have a different influence on the population den-sity of the four groups. These models can be used to predict the average species populationdensity over large areas and be used to explore macroecological patterns and inform conservationanalyses.

Mapping earthworm communities in Europe
Rutgers et al.
Applied soil ecology, 2016

Vers de terre théorique europe


Global nutrient transport in a world of giants
Doughty et al.
PNAS 2015

The past was a world of giants, with abundant whales in the sea and large animals roaming the land. However, that world came to an end following massive late-Quaternary megafauna extinctions on land and widespread population reductions in great whale populations over the past few centuries. These losses are likely to have had important consequences for broad-scale nutrient cycling, because recent literature suggests that large animals disproportionately drive nutrient movement. We estimate that the capacity of animals to move nutrients away from concentration patches has decreased to about 8% of the preextinction value on land and about 5% of historic values in oceans

animal-nutrient-recycling doughty 2015

Precipitation on land versus distance from the ocean: Evidence for a forest pump of atmospheric moisture
Makarieva et al.
Ecological complexity, 2009

Our results indicate that forest cover plays a major role in the atmospheric circulation and water cycling on land. This suggests a good potential for forest-mediated solutions of the global desertification and water security problems.

The Anthropogenic Greenhouse Era Began Thousands of Years Ago
William F. Ruddiman
Climatic change, 2003

A wide array of archeological, cultural, historical and geologic evidence points to viable explanations tied to anthropogenic changes resulting from early agriculture in Eurasia, including the start of forest clearance by 8000 years ago and of rice irrigation by 5000 years ago. In recent millennia, the estimated warming caused by these early gas emissions reached a global-mean value of ∼ 0.8 °C and roughly 2 °C at high latitudes, large enough to have stopped a glaciation of northeastern Canada predicted by two kinds of climatic models.