Andrew Abraham

Northern Arizona University | NAU · School of Informatics, Computing and Cyber Systems

Many species of large mammals were driven to extinction during the late Pleistocene and early Holocene (approx. 10,000 – 50,000 years ago), with cascading effects on the physical structure of ecosystems and the dispersal of seeds, nutrients, and microbes. However, it remains uncertain whether the parasites associated with these extinct hosts also d...

The stratified nature of tropical forest structure had been noted by early explorers, but until recent use of satellite-based LiDAR (GEDI, or Global Ecosystems Dynamics Investigation LiDAR), it was not possible to quantify stratification across all tropical forests. Understanding stratification is important because by some estimates, a majority of...

Sodium (Na) plays a critical role in the functioning of terrestrial ecosystems. In Na-poor regions, plant consumers may experience Na deficiency and adapt by seeking supplementary Na resources. This can markedly impact animal behavior, space-use, and co-existence, with concomitant impacts on ecosystems. Many studies have noted that Na-seeking behav...

In nutrient-poor wildlife reserves it has become common-practice to provide supplemental mineral resources for wildlife. Yet, the impacts of anthropogenic mineral supplementation on large herbivore nutrition, behaviour, and subsequent impact on ecosystem processes have received little attention. Here, we examine the contribution of anthropogenic mi...

The stratified nature of tropical forest structure had been noted by early explorers, but until recent use of satellite-based LiDAR (GEDI, or Global Ecosystems Dynamics Investigation LiDAR), there has been no way to quantify stratification across all tropical forests. Understanding stratification is important because by some estimates, a majority o...

In nutrient-poor wildlife reserves it has become common-place to provide supplemental mineral resources for wildlife. Yet, the impacts of anthropogenic mineral supplementation on community-wide wildlife nutrition, behaviour and subsequent impact on ecosystem processes remain poorly understood. Here, we examine the contribution of anthropogenic mine...

Ecological restoration is critical for climate and biodiversity resilience over the coming century. Today, there is strong evidence that wildlife can significantly influence the distribution and stoichiometry of elements across landscapes, with subsequent impacts on the composition and functioning of ecosystems. Consequently, any anthropogenic acti...

Background Determining the life-history traits of extinct species is often difficult from skeletal remains alone, limiting the accuracy of studies modeling past ecosystems. However, the analysis of the degraded endogenous bacterial DNA present in paleontological fecal matter (coprolites) may enable the characterization of specific traits such as th...

Phosphorus (P) is essential for all life on Earth and sustains food production. Yet, the easily accessible deposits of phosphate-rich rock, which underpin the green revolution are becoming rarer. Here we propose a mechanism to help alleviate the problem of “peak phosphorus”. In the past, wild animals played a large role in returning P from ocean de...

Animals concentrate key nutrients in their bodies. In fenced wildlife reserves where nutrient input and/or retention is low, the off‐site removal of animals may constitute a significant loss of nutrients for the ecosystem. Here we add wildlife capture and removal into the phosphorus (P) and calcium (Ca) budget for a 121,700 ha fenced game reserve l...

A better understanding of carbon use efficiency (CUE) and carbon allocation during disturbance is critical to improve simulations of the global carbon cycle and understanding future climate impacts. Forest thinning of high‐stem density, high elevation dry western US forests is becoming more common to reduce severe fire danger but there are uncertai...

Animals are important vectors for transporting seeds, nutrients and microbes across landscapes. However, models that quantify the magnitude of these ecosystem services across a broad range of taxa often rely on generalised mass‐based scaling parameters for gut passage time. This relationship is weak and fundamentally breaks down when considering in...

Can multicellular life be distinguished from single cellular life on an exoplanet? We hypothesize that abundant upright photosynthetic multicellular life (trees) will cast shadows at high sun angles that will distinguish them from single cellular life and test this using Earth as an exoplanet. We first test the concept using unmanned aerial vehicle...

The Late Quaternary extinctions of megafauna (defined as animal species > 44.5 kg) reduced the dispersal of seeds and nutrients, and likely also microbes and parasites. Here we use body‐mass based scaling and range maps for extinct and extant mammal species to show that these extinctions led to an almost seven‐fold reduction in the movement of gut‐...

Humans and natural systems face three pressing concerns: the loss of large animal biodiversity, eutrophication of many aquatic systems, and the need to better recycle phosphorus. Here we propose a mechanism to help alleviate these problems. Some have hypothesized that we are approaching “peak phosphorus,” where phosphorus may become more expensive...

Forest thinning of overgrown Western US forests is becoming more common to reduce severe fire danger. Such large changes in forest structure could impact the global carbon budget, but despite being relatively well studied, there are uncertainties on how forest thinning may impact forest carbon use efficiency, carbon allocation, and herbivore abunda...

Can multicellular life be distinguished from single cellular life on an exoplanet? We hypothesize that abundant upright photosynthetic multicellular life (trees) will cast shadows at high sun angles that will distinguish them from single cellular life and test this using Earth as an exoplanet. We first test the concept using Unmanned Arial Vehicles...

A prominent signal of the Anthropocene is the extinction and population reduction of the megabiota—the largest animals and plants on the planet. However, we lack a predictive framework for the sensitivity of megabiota during times of rapid global change and how they impact the functioning of ecosystems and the biosphere. Here, we extend metabolic s...

The general observation that secondary consumers ingest highly digestible food and have simple short guts and small abdominal cavities intuitively results in the assumption that mammalian carnivores carry less digesta in their gut compared to herbivores. Due to logistic constraints, this assumption has not been tested quantitatively so far. In this...

The Late Quaternary extinctions of megafauna (defined as animal species >44.5 kg) reduced the dispersal of seeds and nutrients, and likely also microbes and parasites. Here we use body-mass based scaling and range maps for extinct and extant mammal species to show that these extinctions led to an almost seven-fold reduction in the movement of gut-t...

Many mechanisms have been hypothesized to explain Bergmanns rule - the correlation of body size with latitude. However, it is not feasible to assess the contribution of hypothesised mechanisms by experimental manipulation or statistical correlation. Here, we evaluate two of the principal hypothesised mechanisms, related to thermoregulation and reso...

A prominent signal of the Anthropocene is the extinction and population reduction of the megabiota – the largest animals and plants on the planet. However, we lack a predictive framework for the sensitivity of megabiota during times of rapid global change and how they impact the functioning of ecosystems and the biosphere. Here, we extend metabolic...

The leaf economic spectrum (LES) describes a set of universal trade-offs between leaf mass per area (LMA), leaf nitrogen (N), leaf phosphorus (P) and leaf photosynthesis that influence patterns of primary productivity and nutrient cycling. Many questions regarding vegetation-climate feedbacks can be addressed with a better understanding of LES trai...

It is known that tropical grasslands such as Serengeti host large populations of arbuscular mycorrhizal ( AM ) fungi and that they respond to abiotic and biotic factors. It is also known that AM symbioses are important for the uptake of essential plant nutrients, which, in turn, influences the biomass and nutritional quality of herbivores and their...