Paul R. Ehrlich

Stanford University | SU

Applied to human populations, the ecological concept of carrying capacity is necessarily complicated because human beings are the “ultimate ecosystem engineers” who deliberately and successfully moderate their environment for their benefit. For at least that last few hundred years, human ingenuity, access to massive stocks of fossil fuels, and tech...

Mass extinctions during the past 500 million y rapidly removed branches from the phylogenetic tree of life and required millions of years for evolution to generate functional replacements for the extinct (EX) organisms. Here we show, by examining 5,400 vertebrate genera (excluding fishes) comprising 34,600 species, that 73 genera became EX since 15...

How human modification of native habitats changes the feeding patterns and nutritional ecology of tropical birds is critical to conserving avian biodiversity, but tropical bird diets are laborious to investigate using the traditional methods of diet analysis. Stable isotope analysis provides a cost-effective and efficient proxy to identify general...

Humanity must commit to transformative change on all levels in order to address the climate emergency and biodiversity collapse. In particular, stabilizing and ultimately reducing the human population size is necessary to ensure the long-term wellbeing of our species and other life on Earth. We show how this transition can be accomplished in an equ...

Humanity has triggered the sixth mass extinction episode since the beginning of the Phanerozoic. The complexity of this extinction crisis is centred on the intersection of two complex adaptive systems: human culture and ecosystem functioning, although the significance of this intersection is not properly appreciated. Human beings are part of biodiv...

The increasing frequency of extreme events, exogenous and endogenous, poses challenges for our societies. The current pandemic is a case in point; but "once-in-a-century" weather events are also becoming more common, leading to erosion, wildfire and even volcanic events that change ecosystems and disturbance regimes, threaten the sustainability of...

In their comment on our paper “Underestimating the challenges of avoiding a ghastly future” (Bradshaw et al., 2021), Bluwstein et al. (2021) attempt to contravene our exposé of the enormous challenges facing the entire human population from a rapidly degrading global environment. While we broadly agree with the need for multi-disciplinary solutions...

We report three major and confronting environmental issues that have received little attention and require urgent action. First, we review the evidence that future environmental conditions will be far more dangerous than currently believed. The scale of the threats to the biosphere and all its lifeforms — including humanity — is in fact so great th...

Global environmental change challenges humanity because of its broad scale, long-lasting, and potentially irreversible consequences. Key to an effective response is to use an appropriate scientific lens to peer through the mist of uncertainty that threatens timely and appropriate decisions surrounding these complex issues. Identifying such corridor...

Eminent public intellectual who served science and society

Significance The ongoing sixth mass extinction may be the most serious environmental threat to the persistence of civilization, because it is irreversible. Thousands of populations of critically endangered vertebrate animal species have been lost in a century, indicating that the sixth mass extinction is human caused and accelerating. The accelerat...

We consider two aspects of the human enterprise that profoundly affect the global environment: population and consumption. We show that fertility and consumption behavior harbor a class of externalities that have not been much noted in the literature. Both are driven in part by attitudes and preferences that are not egoistic but socially embedded;...

Significance As agricultural lands rapidly expand in the tropics, they become critical for the future of tropical biodiversity, but little is known about their long-term conservation value. Over 12 years in Costa Rica, we measured the abundance and diversity of birds in agricultural areas and embedded forest remnants. We recorded 185 bird species i...

Journal of Population and Sustainability Journal Vol.2 No.2. Papers by: DAVID SAMWAYS - Anthropocentrism – The Origin of Environmental Degradation? UGO BARDI - A Seneca Collapse for the World’s Human Population? DOUGLAS E. BOOTH - Postmaterial Experience Economics, Population, and Environmental Sustainability. WILLIAM N. RYERSON - The Hidden Gem o...

Virtually all trends, biophysical and socioeconomic, suggest that levels of hunger, already high, will only increase as the human population grows and its life-support systems are degraded. Steps that might ameliorate the situation are, unhappily, nowhere in sight.

Significance The strong focus on species extinctions, a critical aspect of the contemporary pulse of biological extinction, leads to a common misimpression that Earth’s biota is not immediately threatened, just slowly entering an episode of major biodiversity loss. This view overlooks the current trends of population declines and extinctions. Using...

Climate change, biodiversity loss, antibiotic resistance, and other global challenges pose major collective action problems: A group benefits from a certain action, but no individual has sufficient incentive to act alone. Formal institutions, e.g., laws and treaties, have helped address issues like ozone depletion, lead pollution, and acid rain. Ho...

Today’s population–resource–environment situation is summarized in comparison with that pertaining in 1968 when The Population Bomb was published. The human predicament is now much more serious, since the human population has more than doubled in size since 1968, key resources are much more depleted, and environmental deterioration is substantially...

Despite solid evidence from the scientific community about climate disruption, much of the US public remains unconvinced about the reality of anthropogenic change, and national governments have been slow to undertake major steps to deal with the climate crisis. In order to understand this lack of foresight intelligence regarding climate disruption,...

Abstract We maintain that humanity’s grand challenge is solving the intertwined problems of human population growth and overconsumption, climate change, pollution, ecosystem destruction, disease spillovers, and extinction, in order to avoid environmental tipping points that would make human life more difficult and would irrevocably damage planetary...

Extract Paul was just 15 when he met Michener (Mich), who was curator of Lepidoptera at the American Museum of Natural History. He seemed to be very old to Paul (Mich was 29) and Paul thought even then that Mich was a great scientist (he was right). Mich was doing research on the taxonomy of butterflies and moths because he couldn’t find employment...

We conducted extensive mist netting and radio tracking of common frugivorous, seed-dispersing and tropical forest-dwelling blue-crowned manakins (Lepidothrix coronata; BCMA) and white-ruffed manakins (Corapipo altera; WRMA) to study their habitat use, movements, breeding success, and seed dispersal potential in the fragmented landscape of southern...

Achieving universal food security is a staggering challenge, especially in a world with an expanding population, accelerating consumption, and many signals of a deteriorating global environment (1). Some claim that population size and growth are irrelevant, and that the solution is a more equitable distribution of income, wealth, and available food...

If I were young again, I’d start another butterfly collection tomorrow. Little has given me such pleasure in a long life as has science, and especially collecting butterflies and using them as tools to answer questions in evolution and ecology. And nothing has connected me to more adventures and interesting people. This was brought home to me again...

Kirchhoff (1) highlights inherent difficulties in organizing the rationales that motivate conservation. The author provides two critiques: first, that our conservation objective typology aggregates conflicting subgoals, and second that the objectives are not mutually exclusive (2). We contend that homogenous and mutually exclusive typologies are ne...

Though separated by thousands of miles, the United States and Australia have much in common. Geographically both countries are expansive—the United States is the fourth largest in land mass and Australia the sixth—and both possess a vast amount of natural biodiversity. At the same time, both nations are on a crash course toward environmental destru...

The Pope has made a strong call for action on climate change, but it fails to address the complex linkages between sustainable development and demographic growth.

Significance Conservationists have become embroiled in debates over different motivations for conserving nature. One path forward is to acknowledge that nature is valued for many reasons and that managing for one objective can fail to achieve others. We categorize conservation objectives and provide a framework for comparing trade-offs between alte...

his book shows us the face of Earth’s sixth great mass extinction, revealing that this century is a time of darkness for the world’s birds and mammals. In The Annihilation of Nature, three of today’s most distinguished conservationists tell the stories of the birds and mammals we have lost and those that are now on the road to extinction. These tra...

A central responsibility of societies should be supplying adequate nourishment to all. For roughly a third of the global human population, that goal is not met today. More ominously, that population is projected to increase some 30% by 2050. The intertwined natural and social systems, that must meet the challenge of producing and equitably distribu...

The oft-repeated claim that Earth's biota is entering a sixth " mass extinction " depends on clearly demonstrating that current extinction rates are far above the " background " rates prevailing in the five previous mass extinctions. Earlier estimates of extinction rates have been criticized for using assumptions that might overestimate the severit...

Many ecologists and environmental scientists witnessing the scale of current environmental change are becoming increasingly alarmed about how humanity is pushing the boundaries of the Earth’s systems beyond sustainable levels. The world urgently needs global society to redirect itself toward a more sustainable future: one that moves intergeneration...

In a sense, civilization has always lacked food security; how well-fed people would be at a given time has been uncertain. Famines have been common throughout history. Today some 2-3 billion people are food-insecure, with insecurity defined as “open to danger or threat; lack of protection.” Roughly 800 million are frankly hungry, and another perhap...

An age-old conflict around a seemingly simple question has resurfaced: why do we conserve nature? Contention around this issue has come and gone many times, but in the past several years we believe that it has reappeared as an increasingly acrimonious debate between, in essence, those who argue that nature should be protected for its own sake (intr...

Difficulty in characterizing the relationship between climatic variability and climate change vulnerability arises when we consider the multiple scales at which this variation occurs, be it temporal (from minute to annual) or spatial (from centimetres to kilometres). We studied populations of a single widely distributed butterfly species, Chlosyne...

Comment to: Dalerum, F. 2014. Identifying the role of conservation biology for solving the environmental crisis. AMBIO 43. Doi: 10.1007/s13280-014-0546-3. Frederik Dalerum (2014) has nicely summarized what many of us consider the basic question of how conservation biologists should allocate their time in trying to deal with the existential threat t...

Aquaculture is the fastest growing food sector and continues to expand alongside terrestrial crop and livestock production. Using portfolio theory as a conceptual framework, we explore how current interconnections between the aquaculture, crop, livestock, and fisheries sectors act as an impediment to, or an opportunity for, enhanced resilience in t...

Background/Question/Methods Our understanding of how to manage biodiversity is clouded by our weak grasp of its dimensions. Biodiversity is often simplified in management decisions, reduced to a few metrics that reflect only a subset of the reasons for why we care about its conservation. While we do know that biodiversity is valued for many reaso...

Despite their value, coastal ecosystems are globally threatened by anthropogenic impacts, yet how these impacts are driven by economic development is not well understood. We compiled a multifaceted dataset to quantify coastal trends and examine the role of economic growth in China's coastal degradation since the 1950s. Although China's coastal popu...

Stratospheric injection of sulphate aerosols has been advocated as an emergency geoengineering measure to tackle dangerous climate change, or as a stop-gap until atmospheric carbon dioxide levels are reduced. But it may not prove to be the game-changer that some imagine.

The Anthropocene is recognized (though not yet formally defined) as the time when human impacts are widespread on Earth. While some of the impacts are essential to supporting large human populations and can be sustainable in the long run, others can irretrievably damage the life support systems upon which the global society has come to depend, or s...

The future of biodiversity and ecosystem services depends largely on the capacity of human-dominated ecosystems to support them, yet this capacity remains largely unknown. Using the framework of countryside biogeography, and working in the Las Cruces system of Coto Brus, Costa Rica, we assessed reptile and amphibian assemblages within four habitats...

Comprehensive assessments have shown the wide variety of severe environmental problems facing and caused by humanity (e.g. Ehrlich and Ehrlich 2013 ; IPCC (Intergovernmental Panel on Climate Change) 2007 ; MEA (Millennium Ecosystem Assessment) 2005 ; Mitchell et al. 2006 ). These problems result largely from the activities of a human population who...

The most serious threat to global sustainability is one on which there is widespread agreement: the growing difficulty of avoiding large-scale famines. Measures to improve food security have never been more urgently needed, and sadly current warnings probably underestimate the food problem. For example, in addition to nearly a billion people “hungr...

The Night Parrot Pezoporus occidentalis, known from just two specimens and with no confirmed sightings for just over 100 years, and having declined from being one of the most widespread of Australian birds, has surely been amongst the most enigmatic birds of the world and deservedly the 'holy grail' for many birders. Amazingly, a population of this...

Humans are the dominant influence affecting patterns of life on the planet. Our demand for food, fuel, and fiber has created a myriad of countryside habitats that collectively amount to the majority of terrestrial and marine ecosystems. Countryside biogeography studies the distribution of biological variation over space and time in human-dominated...

Two central issues concerning biodiversity today are improving one’s knowledge of the roles plants, animals, fungi, and microorganisms play in the functioning of ecosystems and the escalating negative impacts of human beings on those ecosystems. Here the focus is on the latter, starting with the rise of humanity as a geophysical force and then exam...

Prof. Kelly FRS is optimistic about the chances of avoiding a collapse, but sadly we find his arguments entirely unpersuasive. For example, have Malthus (or we) really been wrong about food security? Roughly 850 million people are seriously undernourished (lacking sufficient calories) today, and

Efforts to maximise crop yields are fuelling agricultural intensification, exacerbating the biodiversity crisis. Low-intensity agricultural practices, however, may not sacrifice yields if they support biodiversity-driven ecosystem services. We quantified the value native predators provide to farmers by consuming coffee's most damaging insect pest,...

Background/Question/Methods The most important ethical question facing society and the scientific community today is whether we can prevent the collapse of global civilization in response to today’s “perfect storm” of environmental problems. The interrelated crises of overpopulation, wasteful consumption, rapidly deteriorating life-support system...

Proc. R. Soc. B 279, 67–76. (7 January 2012; Published online 18 May 2011) (doi:10.1098/rspb.2011.0433) We would like to correct two errors in text. On page 70, §3a (Results: Species discovery trends), 9th line, the phrase ‘first-author taxonomists' should be changed to ‘first- and second-author taxonomists’. This is an isolated text error that doe...

Earth is rapidly approaching a tipping point. Human impacts are causing alarming levels of harm to our planet. As scientists who study the interaction of people with the rest of the biosphere using a wide range of approaches, we agree that the evidence that humans are damaging their ecological life-support systems is overwhelming. We further agree...

Sticky Responses A textbook example of an unaccounted-for consequence (externality) of commercial or industrial activity is the production of pollutants where neither the producer nor the buyer bears the cost of using common environmental resources. Dasgupta and Ehrlich (p. 324 ) offer a theoretical analysis of externalities in two other areas of m...

Systems linking people and nature, known as social-ecological systems, are increasingly understood as complex adaptive systems. Essential features of these complex adaptive systems – such as nonlinear feedbacks, strategic interactions, individual and spatial heterogeneity, and varying time scales – pose substantial challenges for modeling. However,...

Environmental problems have contributed to numerous collapses of civilizations in the past. Now, for the first time, a global collapse appears likely. Overpopulation, overconsumption by the rich and poor choices of technologies are major drivers; dramatic cultural change provides the main hope of averting calamity.

Government policies are needed when people’s behaviors fail to deliver the public good. Those policies will be most effective if they can stimulate long-term changes in beliefs and norms, creating and reinforcing the behaviors needed to solidify and extend the public good. It is often the short-term acceptability of potential policies, rather than...

Today, at least two billion people are hungry or need better diets, and most analysts think doubling food production will be required to feed the human population adequately by 2050. A recent excellent study outlined how a required doubling could be achieved, based on five essential steps: stop increasing land for agriculture (to preserve ecosystem...

Ecosystems and socio-economic systems are complex adaptive systems, composed of individual agents with their own selfish agendas. This creates challenges for management, which we explore.

Background/Question/Methods Growing demand for food, fuel, and fiber is driving the intensification and expansion of agricultural land through a corresponding displacement of native woodland, savanna, and shrubland. In the wake of this displacement, it is clear that farmland can support biodiversity through preservation of important ecosystem ele...

Background/Question/Methods It has become increasingly clear that simply giving the public accurate scientific information will not change the public’s behavior with respect to the current environmental emergency. This is clearly illustrated by the efficacy of the well-funded campaign of climate denial, supported by the fossil-fuel industry and a...

The authors offer an ecological frame of reference for political action to change the economic and social trends now deepening the human predicament: overpopulation and continuing population growth, overconsumption by rich societies, resource depletion, environmental degradation, and inequitable distribution of wealth within and between societies....

Quantifying the magnitude of human-induced biodiversity loss is a critical yet daunting challenge. Recently, species extinction rate estimates using island biogeography theory have once again been called into question. Here we highlight two of the many factors making the traditional application of this approach problematic for measuring biodiversit...

Biodiversity is declining from unprecedented land conversions that replace diverse, low-intensity agriculture with vast expanses under homogeneous, intensive production. Despite documented losses of species richness, consequences for β-diversity, changes in community composition between sites, are largely unknown, especially in the tropics. Using a...

In biophysical terms, humanity has never been moving faster nor further from sustainability than it is now. Our increasing population size and per capita impacts are severely testing the ability of Earth to provide for peoples' most basic needs. Awareness of these circumstances has grown tremendously, as has the sophistication of efforts to address...

Sustainability demands changes in human behavior. To this end, priority areas include reforming formal institutions, strengthening the institutions of civil society, improving citizen engagement, curbing consumption and population growth, addressing social justice issues, and reflecting on value and belief systems. We review existing knowledge acro...

Wiersma and Nudds (1) make four main points: (i) the area to be covered by the key conservation sites proposed is a negligible percentage of the ocean; (ii) they doubt the representativeness of our biodiversity patterns; (iii) they question the persistence of the species; and (iv) they claim we do not acknowledge the dynamic nature of ecological sy...

The consequences of biodiversity decline in intensified agricultural landscapes hinge on surviving biotic assemblages. Maintaining crucial ecosystem processes and services requires resilience to natural and anthropogenic disturbances. However, the resilience and stability of surviving biological communities remain poorly quantified. From a 10-y dat...

Supplementary information to: Non-natives: 141 scientists object Full list of co-signatories to a Correspondence published in Nature 475, 36 (2011); doi: 10.1038/475036a. Daniel Simberloff University of Tennessee, Knoxville, Tennessee, USA. dsimberloff@utk.edu Jake Alexander Institute of Integrative Biology, Zurich, Switzerland. Fred Allendorf Univ...

Chemical and physical (abiotic) conditions can be determining factors of community assembly and invasibility, but can this observation be used as a practical tool for habitat creation? Serpentine soils, in particular, have three abiotic components thought to confer invasion resistance: a low Ca:Mg ratio, low water‐retention capacity, and high conce...