Morgan Jayne Trimble

Species Inequality in Scientific Study

Some conservationists argue for a focused effort to protect the most critically endangered species, and others suggest a large-scale endeavor to safeguard common species across large areas. Similar arguments are applicable to the distribution of scientific effort among species. Should conservation scientists focus research efforts on threatened species, common species, or do all species deserve equal attention? We assessed the scientific equity among 1909 mammals, birds, reptiles, and amphibians of southern Africa by relating the number of papers written about each species to their status on the International Union for Conservation of Nature Red List. Threatened large mammals and reptiles had more papers written about them than their nonthreatened counterparts, whereas threatened small mammals and amphibians received less attention than nonthreatened species. Threatened birds received an intermediate amount of attention in the scientific literature. Thus, threat status appears to drive scientific effort among some animal groups, whereas other factors (e.g., pest management and commercial interest) appear to dictate scientific investment in particular species of other groups. Furthermore, the scientific investment per species differed greatly between groups-the mean number of papers per threatened large mammal eclipsed that of threatened reptiles, birds, small mammals, and amphibians by 2.6-, 15-, 216-, and more than 500-fold, respectively. Thus, in the eyes of science, all species are not created equal. A few species commanded a great proportion of scientific attention, whereas for many species information that might inform conservation is virtually nonexistent.

Geographical and taxonomic biases in research on biodiversity in human-modified landscapes

Biodiversity persistence in human-modified landscapes is crucial for conservation and maintaining ecosystem services. Studies of biodiversity in landscapes where humans live, work, and extract resources could support defensible policy-making to manage land-use. Yet, research should cover relevant regions, and biases in study topics should not lead to gaps in the evidence base. We systematically reviewed the literature of biogeography in human-modified landscapes published in eight eminent biogeography, conservation, and ecology journals to assess geographical bias among biomes and geopolitical regions and taxonomic bias among species groups. We compared research output per biome to area, biome type, species richness, proportion of transformed land, and the ratio of transformed to protected land. We also compared research output per geopolitical region to area, proportion of transformed land, the ratio of transformed to protected land, and human population density. Research output was distributed unequally among biomes, geopolitical regions, and species groups. Biome type was a clear factor in research bias, and forest biomes were the subject of 87% of papers, while species richness was not generally associated with bias. Conservation in human-modified landscapes is most important in regions with low protected area coverage, high land conversion, and high pressure from human populations, yet the distribution of published papers did not generally reflect these threats. Seventy-five percent of studies focused on the Americas and Europe, while Africa and Asia were critically understudied. Taxonomically, plants and invertebrates were the most studied groups; however, research output was not correlated with species richness per group. Protected areas alone will not conserve biodiversity in the long term. Thus, a strong biogeographical evidence base is required to support policies for biodiversity maintenance on human-modified land. Under-studied regions and species groups deserve further research to elucidate what, where, and how biodiversity persists in human-modified landscapes to inform conservation policy and enhance efficacy.

Age Determination by Back Length for African Savanna Elephants: Extending Age Assessment Techniques for Aerial-Based Surveys

Determining the age of individuals in a population can lead to a better understanding of population dynamics through age structure analysis and estimation of age-specific fecundity and survival rates. Shoulder height has been used to accurately assign age to free-ranging African savanna elephants. However, back length may provide an analog measurable in aerial-based surveys. We assessed the relationship between back length and age for known-age elephants in Amboseli National Park, Kenya, and Addo Elephant National Park, South Africa. We also compared age- and sex-specific back lengths between these populations and compared adult female back lengths across 11 widely dispersed populations in five African countries. Sex-specific Von Bertalanffy growth curves provided a good fit to the back length data of known-age individuals. Based on back length, accurate ages could be assigned relatively precisely for females up to 23 years of age and males up to 17. The female back length curve allowed more precise age assignment to older females than the curve for shoulder height does, probably because of divergence between the respective growth curves. However, this did not appear to be the case for males, but the sample of known-age males was limited to ≤27 years. Age- and sex-specific back lengths were similar in Amboseli National Park and Addo Elephant National Park. Furthermore, while adult female back lengths in the three Zambian populations were generally shorter than in other populations, back lengths in the remaining eight populations did not differ significantly, in support of claims that growth patterns of African savanna elephants are similar over wide geographic regions. Thus, the growth curves presented here should allow researchers to use aerial-based surveys to assign ages to elephants with greater precision than previously possible and, therefore, to estimate population variables.

Savanna elephant numbers are only a quarter of their expected values

Savannas once constituted the range of many species that human encroachment has now reduced to a fraction of their former distribution. Many survive only in protected areas. Poaching reduces the savanna elephant, even where protected, likely to the detriment of savanna ecosystems. While resources go into estimating elephant populations, an ecological benchmark by which to assess counts is lacking. Knowing how many elephants there are and how many poachers kill is important, but on their own, such data lack context. We collated savanna elephant count data from 73 protected areas across the continent estimated to hold ~50% of Africa’s elephants and extracted densities from 18 broadly stable population time series. We modeled these densities using primary productivity, water availability, and an index of poaching as predictors. We then used the model to predict stable densities given current conditions and poaching for all 73 populations. Next, to generate ecological benchmarks, we predicted such densities for a scenario of zero poaching. Where historical data are available, they corroborate or exceed benchmarks. According to recent counts, collectively, the 73 savanna elephant populations are at 75% of the size predicted based on current conditions and poaching levels. However, populations are at <25% of ecological benchmarks given a scenario of zero poaching (~967,000)—a total deficit of ~730,000 elephants. Populations in 30% of the 73 protected areas were <5% of their benchmarks, and the median current density as a percentage of ecological benchmark across protected areas was just 13%. The ecological context provided by these benchmark values, in conjunction with ongoing census projects, allow efficient targeting of conservation efforts.