Conventional approaches that focus only on species abundance can tell us how animal populations have changed, for example, to what extent elephant numbers have fallen in a given region. But translating these changes into ecosystem-wide shifts is difficult, and doing so across thousands of species in a variety of ecosystems is a mammoth challenge.<\/p>\n
Ecological energetics quantifies how species shape ecosystems through their food intake, their ecological roles, and the energy that flows through them.<\/p>\n
Energy is constantly being transferred from vegetation to animals, between animals, and from animals back to the environment. The natural realm isn\u2019t a static space with animals tacked onto it; these are living, breathing worlds with which animals inhabit and interact. Take vegetation: animals directly shape the landscape by grazing and browsing (eating), and indirectly through the dispersal of seeds and nutrients (e.g., through pooping).<\/p>\n
In the paper, Loft and his colleagues focused on nearly 3,000 bird and mammal species in sub-Saharan Africa. They considered 23 ecosystem functions, ranging from pollination to nutrient disposal, grouped them into 10 function classes, and then grouped the animals according to the ecological roles they play. By taking into account species present in an area, their abundance, body sizes, diets, and metabolic rates, they turned the animal\u2019s food consumption into a measure of energy flow: kilojoules per square meter per year. This formula captures how much energy animals in an ecological function guild consume and expend, a proxy for the power channeled into an environmental function.<\/p>\n The authors traced the extent to which energy flows have diminished compared to historical values, i.e., before humans began altering them in significant ways. In this case, the authors took as their baseline the year 1700.<\/p>\n In general, the \u201cecological power\u201d of wild mammals and birds weakened drastically, by about 60%, in areas that had been converted to agricultural land in the study area. However, in well-managed protected areas, ecological functions are almost 90% intact. For example, the study documented a striking decline in ecological functions performed by megafauna such as elephants outside protected areas in sub-Saharan Africa.<\/p>\n \u201cThe paper offers quite unique and novel insights,\u201d Santiago Soliveres Codina, an ecologist at the University of Alicante in Spain, who wasn\u2019t involved in the study, told Mongabay by email. \u201cThe nice thing about using the energetic approach is that it is able to establish a functional \u2018importance\u2019 for each species, comparable across species, based on how much energy it moves throughout the ecosystem, and between ecosystems.\u201d<\/p>\n The approach better captures the relative importance of animals to ecosystems by accounting for food consumption rather than only biomass or size. Take, for example, birds or small mammals like rodents, which are small in size but consume and process energy faster.<\/p>\n \u201cThey burn through calories very quickly. And all of that eating has a big impact on ecosystems, including by spreading seeds, controlling insect and pest populations, and pollinating plants, among other impacts,\u201d Loft said.<\/p>\n For Codina, this finding is striking. \u201cWhat was quite interesting to see for me is the unexpected[ly] large role of birds and small mammals, despite their small sizes, in the energy flow across ecosystems,\u201c he said, \u201cor how the key animals change from one type of ecosystem [forest] to another [drylands].\u201d<\/p>\n A method that relies solely on changes in animal abundance will not faithfully capture ecosystem changes, as it assigns equal weight to all species. \u201cIn reality, some species disproportionately affect ecosystem function owing to their population densities, body sizes, dietary preferences, rates of food consumption and features,\u201d the paper notes.<\/p>\n Innovative as it is, ecological power alone may not capture all the ways ecosystems have changed in response to human-caused impacts.<\/p>\n \u201cIn particular, energy flow needs to remain coupled with consideration of the number of species contributing to energy flow to avoid wrongly labelling the persistence of a few generalist species as ecological intactness,\u201d the paper said.<\/p>\n Analyzing ecological processes this way is also a data-heavy exercise. Codina described the approach as \u201creally data demanding,\u201d adding that the data on current and historical abundances of wild animals rely on models and estimates. \u201cSolid as they are, of course, they will have some errors,\u201d he said.<\/p>\n Because calculating energy flows isn\u2019t just about how much food animals eat, but the rates at which they metabolize the food, Codina raised the possibility that metabolic efficiency could have changed in wild animals living on lands impacted by humans, a factor the study didn\u2019t account for.<\/p>\n \u201cAny large study such as this one rests on many assumptions, combines many datasets, and therefore includes a substantial amount of uncertainty,\u201d Loft said, adding \u201c[it] may not be able to usefully guide action within a specific ecosystem.\u201d<\/p>\n However, such analysis can shed light on the \u201cbig picture changes to the world\u2019s biodiversity and its ecosystems,\u201d Loft said.<\/p>\n Codina agreed that these kinds of results can help shape conservation policy. They \u201ccan help when choosing which species to reintroduce first in restoration programs, or which places or species to prioritize in conservation,\u201d he said.<\/p>\n Banner image: An African lion in Uganda. Image by Julie Larsen \u00a9WCS.<\/p>\n \u00a0<\/p>\n Citations:<\/p>\n Loft, T., Oliveras Menor, I., Stevens, N., Beyer, R., Clements, H. S., Santini, L., \u2026 Malhi, Y. (2025). Energy flows reveal declining ecosystem functions by animals across Africa. Nature. doi:10.1038\/s41586-025-09660-1<\/a><\/p>\n Foden, W. (2025). What changing energy flows reveal about Africa\u2019s ecosystems. Nature. doi:10.1038\/d41586-025-03215-0<\/a><\/p>\n Antunes, A. C., Berti, E., Brose, U., Hirt, M. R., Karger, D. N., O\u2019Connor, L. M., \u2026 Gauzens, B. (2024). Linking biodiversity, ecosystem function, and nature\u2019s contributions to people: A macroecological energy flux perspective. Trends in Ecology & Evolution, 39(5), 427-434. doi:10.1016\/j.tree.2024.01.004<\/a><\/p>\n ![\"A](\"https:\/\/www.newsbeep.com\/il\/wp-content\/uploads\/2025\/12\/a.-Julie-Larsen-\u00a9WCS_1635_Jacksons-Hartebeest-in-wild_UGA_06-28-10.jpg\")
<\/a>A Jackson\u2019s hartebeest in Uganda. Image by Julie Larsen \u00a9WCS.<\/p>\n![\"An](\"https:\/\/www.newsbeep.com\/il\/wp-content\/uploads\/2025\/12\/g.-Julie-Larsen-\u00a9WCS-7459-African-Fish-Eagle-UGA-scaled.jpg\")
<\/a>An African fish eagle in Uganda. Image by Julie Larsen \u00a9WCS.<\/p>\n <\/p>\n