Justin Kitzes

Approaching a state shift in Earth’s biosphere

Localized ecological systems are known to shift abruptly and irreversibly from one state to another when they are forced across critical thresholds. Here we review evidence that the global ecosystem as a whole can react in the same way and is approaching a planetary-scale critical transition as a result of human influence. The plausibility of a planetary-scale ‘tipping point’ highlights the need to improve biological forecasting by detecting early warning signs of critical transitions on global as well as local scales, and by detecting feedbacks that promote such transitions. It is also necessary to address root causes of how humans are forcing biological changes.

The Ecological Footprint of cities and regions: comparing resource availability with resource demand

Cities and regions depend on resources and ecological services from distant ecosystems. The well-being of city and region residents is affected by both the health and availability of these ecosystems, especially in todays ecologically strained world. The management of a city or regions resource metabolism, including the natural capital that supports these flows, is becoming increasingly a central concern to cities and regions that want to succeed. Urban infrastructure is long-lasting and influences resource needs for decades to come: which cities are building future resource traps, and which are opportunities for resource-efficient and more competitive lifestyles? Reliable measures comparing the supply of natural capital to human demand are indispensable for managing resource metabolism, as they help identify challenges, set targets, track progress and drive policies for sustainability. This paper describes one such measurement tool: the Ecological Footprint. After explaining the assumptions behind the Footprint and describing some representative findings, it provides examples of how this resource accounting tool can assist local governments in managing their ecological assets, and support their sustainability efforts.

Shrink and share: humanity's present and future Ecological Footprint

Sustainability is the possibility of all people living rewarding lives within the means of nature. Despite ample recognition of the importance of achieving sustainable development, exemplified by the Rio Declaration of 1992 and the United Nations Millennium Development Goals, the global economy fails to meet the most fundamental minimum condition for sustainability—that human demand for ecosystem goods and services remains within the biospheres total capacity. In 2002, humanity operated in a state of overshoot, demanding over 20% more biological capacity than the Earths ecosystems could regenerate in that year. Using the Ecological Footprint as an accounting tool, we propose and discuss three possible global scenarios for the future of human demand and ecosystem supply. Bringing humanity out of overshoot and onto a potentially sustainable path will require managing the consumption of food, fibre and energy, and maintaining or increasing the productivity of natural and agricultural ecosystems.

An exploration of the mathematics behind the ecological footprint

Introduced in the early 1990s, the ecological footprint has become a well-known and widespread environmental accounting tool. It measures human demand on nature and compares this to the availability of regenerative capacity on the planet. The method expresses human demand in terms of global hectares – i.e. biologically productive hectares with world-average productivity necessary for resource production and waste assimilation. Almost 15 years of research application and methodological advancements have made the ecological footprint an increasingly robust theoretical framework, and it continues to be refi ned. This article documents the most updated footprint methodology and focuses on the mathematics that supports footprint and biocapacity accounts, as well as its underlying factors such as equivalence and yield factors. To clarify the meaning and the usefulness of footprint and biocapacity reported in terms of global hectares, an in-depth description of the units of measure is presented. Finally, the different research questions that emerge when reporting data in nation-specifi c hectares as opposed to global hectares are investigated.

Thinking about knowing: conceptual foundations for interdisciplinary environmental research

Working across knowledge-based research programmes, rather than institutional structures, should be central to interdisciplinary research. In this paper, a novel framework is proposed to facilitate interdisciplinary research, with the goals of promoting communication, understanding and collaborative work. Three core elements need to be addressed to improve interdisciplinary research: the types (forms and functions) of theories, the underlying philosophies of knowledge and the combination of research styles; these three elements combine to form the research programme. Case studies from sustainability science and environmental security illustrate the application of this research programme-based framework. This framework may be helpful in overcoming often oversimplified distinctions, such as qualitative/quantitative, deductive/inductive, normative/descriptive, subjective/objective and theory/practice. Applying this conceptual framework to interdisciplinary research should foster theoretical advances, more effective communication and better problem-solving in increasingly interdisciplinary environmental fields.

Beyond the species–area relationship: improving macroecological extinction estimates

Summary The species–area relationship is often used to predict extinction rates following habitat loss and climate change. This metric, however, has several shortcomings for conservation applications, as it does not predict extinction risk for individual species, only predicts the expected number of extinctions without an associated measure of uncertainty, and assumes that a species is protected if one individual of a species remains in a landscape. Here, we propose two new metrics, the extinction–area relationship and probabilistic species–area relationship, that address these shortcomings, and present equations for each metric based on empirically well-supported species abundance and spatial abundance distributions. Extinction predictions are found to be strongly influenced by the choice of a minimum abundance required for a species to be considered protected, a parameter that cannot be adjusted explicitly in the classic power law form of the species–area relationship. These new metrics provide a flexible and theoretically grounded means of applying macroecological principles to the prediction of extinction.

Consumption-Based Conservation Targeting: Linking Biodiversity Loss to Upstream Demand through a Global Wildlife Footprint

Abstract Although most conservation efforts address the direct, local causes of biodiversity loss, effective long‐term conservation will require complementary efforts to reduce the upstream economic pressures, such as demands for food and forest products, which ultimately drive these downstream losses. Here, we present a wildlife footprint analysis that links global losses of wild birds to consumer purchases across 57 economic sectors in 129 regions. The United States, India, China, and Brazil have the largest regional wildlife footprints, while per‐person footprints are highest in Mongolia, Australia, Botswana, and the United Arab Emirates. A US

Large Roads Reduce Bat Activity across Multiple Species

100 purchase of bovine meat or rice products occupies approximately 0.1 km2 of wild bird ranges, displacing 1–2 individual birds, for 1 year. Globally significant importer regions, including Japan, the United Kingdom, Germany, Italy, and France, have large footprints that drive wildlife losses elsewhere in the world and represent important targets for consumption‐focused conservation attention.

Taxon Categories and the Universal Species-Area Relationship (A Comment on Sizling et al., "Between Geometry and Biology: The Problem of Universality of the Species-Area Relationship")

Although the negative impacts of roads on many terrestrial vertebrate and bird populations are well documented, there have been few studies of the road ecology of bats. To examine the effects of large roads on bat populations, we used acoustic recorders to survey bat activity along ten 300 m transects bordering three large highways in northern California, applying a newly developed statistical classifier to identify recorded calls to the species level. Nightly counts of bat passes were analyzed with generalized linear mixed models to determine the relationship between bat activity and distance from a road. Total bat activity recorded at points adjacent to roads was found to be approximately one-half the level observed at 300 m. Statistically significant road effects were also found for the Brazilian free-tailed bat (Tadarida brasiliensis), big brown bat (Eptesicus fuscus), hoary bat (Lasiurus cinereus), and silver-haired bat (Lasionycteris noctivagans). The road effect was found to be temperature dependent, with hot days both increasing total activity at night and reducing the difference between activity levels near and far from roads. These results suggest that the environmental impacts of road construction may include degradation of bat habitat and that mitigation activities for this habitat loss may be necessary to protect bat populations.

Inferring regional-scale species diversity from small-plot censuses.

A theory of macroecology based on the maximum information entropy (MaxEnt) inference procedure predicts that the log-log slope of the species-area relationship (SAR) at any spatial scale is a specified function of the ratio of abundance, N(A), to species richness, S(A), at that scale. The theory thus predicts, in generally good agreement with observation, that all SARs collapse onto a specified universal curve when local slope, z(A), is plotted against N(A)/S(A). A recent publication, however, argues that if it is assumed that patterns in macroecology are independent of the taxonomic choices that define assemblages of species, then this principle of “taxon invariance” precludes the MaxEnt-predicted universality of the SAR. By distinguishing two dimensions of the notion of taxon invariance, we show that while the MaxEnt-based theory predicts universality regardless of the taxonomic choices that define an assemblage of species, the biological characteristics of assemblages should under MaxEnt, and do in reality, influence the realism of the predictions.