The loss of a keystone species can theoretically lead to large social costs because their complex ecosystem interactions may be important for environmental quality. We quantify these effects for the case of vultures in India where they play an important role in removing livestock carrion from the environment. The expiration of a patent for a common chemical painkiller led to its increased use in cattle, unexpectedly rendering carcasses fatal to vultures, leading to a catastrophic and near-total population collapse. Using habitat range maps for the affected species, we compare high to low vulture suitability districts before and after the patent for the painkiller expired. We find that, on average, all-cause death rates increased by more than 4% in vulture-suitable districts after the vultures nearly went extinct. We find suggestive evidence that feral dog populations and rabies increased, and that water quality deteriorated in the affected regions. These mechanisms are consistent with the loss of the scavenging function of the vultures. Quantifying the costs of biodiversity losses has critical implications for optimal investments into species conservation and rehabilitation.

Media (Wakelet Summary): VoxDev (reprinted at Ideas for India: English, Hindi), The Pie Podcast, economiate, The Economist, News from Science, BBC (Science in Action, CBS, NYT, CBC, Vox, Salon, The Hindu, Anthropocene Magazine, Seznam Zprávy (Czech), Relevant (Hebrew), WaPo, NDTV

Biodiversity loss is accelerating, yet we know little about how these ecosystem disruptions affect human well-being. Ecologists have documented both the importance of bats as natural predators of insects as well as their population declines after the emergence of a wildlife disease, resulting in a potential decline in biological pest control. In this work, I study how species interactions can extend beyond an ecosystem and affect agriculture and human health. I find that farmers compensated for bat decline by increasing their insecticide use by 31.1%. The compensatory increase in insecticide use by farmers adversely affected health—human infant mortality increased by 7.9% in the counties that experienced bat die-offs. These findings provide empirical validation to previous theoretical predictions about how ecosystem disruptions can have meaningful social costs.

PBS NewsHour, NYT, Vox, WaPo, The Guardian, Le Monde (French), New Scientist,  Newsweek, France24, BBC (45:00), CBC, AFP Wire, Science News, Davidson Institute (Hebrew), Deutschlandfunk (German), Smithsonian Magazine, Mongabay, The Pie Podcast

With many fish populations around the world overfished, countries are increasingly passing laws to prevent overfishing and rebuild depleted stocks, an objective adopted in the UN Sustainable Development Goals. However, some elected officials, scientists, and industry groups in the US and Europe have questioned whether such policies have gone too far, resulting in “underfishing,” to the economic detriment of fishing communities. This idea is influencing debate over reauthorizing the US Magnuson-Stevens Act (MSA), which shares key features with fishing policies in the European Union (EU) and Canada and is regarded internationally as a benchmark fishing law. Analyzing two decades of data on 170 US fish stocks, we find that the reasons some species are fished less than others are varied, and the MSA is only sometimes the primary factor. In many cases, fishers are fishing less of a species because they find it unprofitable.

Environmental policies often draw criticism due to their potential impacts on labor market outcomes. Previous work has studied sector-specific impacts following air quality regulations, or examined overall employment effects of land-use policies. In the case of the protection of the Northern Spotted Owl in the 1990s under the Endangered Species Act, millions of acres of highly productive federal timberland in the Pacific Northwest were set aside. Concerns regarding declining employment in the timber industry following the listing are often mentioned as a cautionary tale regarding future listings under the Act. However, disentangling the policy impact from other economic factors affecting employment such as recessions and sector-specific trends is challenging. Here we exploit the 1990 listing of the owl to identify the impact of land protections on labor market outcomes in the timber industry. Our main results indicate large reductions in timber industry employment and the number of establishments, by 28.1% and 9.5%, that persist even a decade after the listing, reflecting a loss of 32,676 jobs in the Lumber and Wood Products sector. We find heterogeneous effects with areas that have larger shares of protected federal timberland experiencing larger declines in employment. Our findings indicate land protection policies may pose significant employment impacts to land-reliant industries.

Energy and Environment News, Portland Business Journal

The influence of temperature on diversity and ecosystem functioning is well studied; the converse however, that is, how biodiversity influences temperature, much less so. We manipulated freshwater algal species diversity in microbial microcosms to uncover how diversity influenced primary production, which is well documented in biodiversity research. We then also explored how visible-spectrum absorbance and the local thermal environment responded to biodiversity change. Variations in the local thermal environment, that is, in the temperature of the immediate surroundings of a community, are known to matter not only for the rate of ecosystem processes, but also for persistence of species assemblages and the very relationship between biodiversity and ecosystem functioning. In our microcosm experiment, we found a significant positive association between algal species richness and primary production, a negative association between primary production and visible-spectrum absorbance, and a positive association between visible-spectrum absorbance and the response of the local thermal environment (i.e., change in thermal infrared emittance over a unit time). These findings support an indirect effect of algal diversity on the local thermal environment pointing to a hitherto unrecognized biodiversity effect in which diversity has a predictable influence on local thermal environments.

The harvesting of wild animals and plants for international trade affects thousands of species, and compounds ongoing extinction threats such as habitat loss and climate change. The loss of overexploited species can result in cascading effects that reduce overall ecosystem functioning. The primary international framework for preventing the loss of species due to international wildlife trade is the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Given that CITES aims to be as scientifically based as possible, we analyzed how quickly species that are identified by the International Union for Conservation of Nature (IUCN) Red List as being threatened from trade are subsequently protected under CITES. The Red List represents an authoritative body of scientific knowledge regarding extinction risks. We find that in nearly two-thirds of the cases, the CITES process of regulating trade in threatened species lags considerably behind the IUCN identification of species in need of protection from trade. Such delay in the application of scientific knowledge to policy formulation could result in species extinctions. With signatories to CITES set to gather in May to determine which species merit protection, we suggest opportunities to improve this process.

Science News, Independent, New Scientist, NYT

Human activities are increasingly degrading ecosystems, resulting in habitat loss and reduced biodiversity. Extinction rates, a widely used metric of biodiversity loss, are estimated to be around 1000 times as high as those historically experienced on Earth; even the most conservative estimate puts current extinction rates at 114 times as high as the background planetary norm. Simulations project that, under scenarios of increased economic growth and the accompanying land use change, critical habitat will further degrade and biodiversity will decline. Are economic growth and ecosystem conservation incompatible objectives?

Background: Exposure to air pollution in the form of particulate matter smaller than 10 µm in diameter (PM10) has been associated with increased morbidity and mortality. However, since air pollution is correlated with confounding factors that might otherwise affect health, identifying the causal link has proven challenging.
Objectives: To identify the effect of PM10 on hospital admissions due to respiratory illnesses.
Methods: We used the Instrumental Variable (IV) methodology to control for confounding factors affecting hospital admissions. Exploiting the timing of sandstorms as an instrumental variable allows for a better estimate of the relationship between PM10 and hospital admissions. Data on PM concentrations and hospital admissions rates were compiled for Israel’s two largest cities, Jerusalem and Tel Aviv, for 2007–2009. We compared our IV estimates to those derived from a Poisson regression, which is commonly used in the existing literature.
Results: Sandstorms led to an increase of 307 µg/m3 of PM10 concentrations. A 10 µg/m3 increase in PM10 is associated with a 0.8% increase in hospital admissions due to respiratory conditions, using Poisson regression. The same finding was noted using the IV methodology.
Conclusions: The association between PM10 and hospital admission reflects a primarily causal relationship. Instrumental variable methodology could be applied to analysis of the effect of air pollution on hospital admissions.

The location of tide gauges is not random. If their locations are positively (negatively) correlated with sea level rise (SLR), estimates of global SLR will be biased upwards (downwards). Using individual tide gauges obtained from the Permanent Service for Mean Sea Level during 1807–2010, we show that tide gauge locations in 2000 were independent of SLR as measured by satellite altimetry. Therefore these tide gauges constitute a quasi-random sample, and inferences about global SLR obtained from them are unbiased. Using recently developed methods for nonstationary time series, we find that sea levels rose in 7% of tide gauge locations and fell in 4%. The global mean increase is 0.39–1.03 mm/year. However, the mean increase for locations where sea levels are rising is 3.55–4.42 mm/year. These findings are much lower than estimates of global sea level (2.2 mm/year) reported in the literature and adopted by IPCC, and which make widespread use of imputed data for locations which do not have tide gauges. We show that although tide gauge locations in 2000 are uncorrelated with SLR, the global diffusion of tide gauges during the 20th century was negatively correlated with SLR. This phenomenon induces positive imputation bias in estimates of global mean sea levels because tide gauges installed in the 19th century happened to be in locations where sea levels happened to be rising.

Can policy sustainably manage economically valuable biological resources? We find evidence it can, with the use of science-based decision rules. In 1996, with United States fish populations in decline, Congress overhauled fishing laws with scientific thresholds for rebuilding overfished stocks. The law’s impact is contested, and lawmakers have spent a decade debating its reauthorization. We develop the first causally interpretable evaluation of this law, exploiting the fact that the European Union has comparable fisheries but only recently developed similar laws. Compiling the largest dataset to date on US and EU fishery status and management, we examine fish populations that decline to unhealthy levels and measure the effect of a policy that aims to rebuild them to health. We find that treated stocks increase by 50% relative to these counterfactuals. Though the policy constrains catch, we find both catch and revenue ultimately rebound and stabilize at or above baseline levels.

Protecting species’ habitats is globally adopted as the main policy tool to reduce biodiversity losses, yet these protections are hypothesized to conflict with private landowners’ interests. We study the economic consequences of such regulation in the context of the Endangered Species Act (ESA), the most extensive conservation and controversial piece of environmental legislation in US history. Using the most comprehensive data on species conservation efforts, land transactions, and building permits to date, we show evidence that the ESA affects land markets in measurable and economically significant ways. Our findings highlight that the impacts on land values depend on the timing of statutory protection enactment, and the land-use in question. We also find no evidence of the ESA affecting building activity as measured by construction permits.

How do large disruptions to ecosystems affect human well-being? In 1958, China embarked on the “Four Pests Campaign” that aimed to quickly eradicate flies, mosquitoes, rats, and sparrows nationwide, ignoring warnings from scientists that sparrows play important roles in pest control. Historians have long speculated that eradicating sparrows, by letting other pest populations grow out of control, contributed to the Great Famine in China between 1959 and 1961—the largest in human history. This paper combines newly digitized data on historical agricultural productivity in China with habitat suitability modeling methods in ecology to quantitatively test this hypothesis. We show that, after the eradication of sparrows, regions with a one standard deviation higher sparrow suitability score experienced an additional 5.3% (8.7%) decline in rice (wheat) output, as compared to their low-suitability counterparts. We further document that the food procurement system exacerbated the negative productivity shock in high-sparrow suitability counties, despite farmers’ attempts to mitigate pest risks by growing below-ground crops that are less vulnerable to crop pests. Consequently, counties with a one standard deviation higher sparrow suitability score experienced an elevated death rate of 3.3 deaths per 1,000 people during the Great Famine.

Monitoring systems for diseases and pests are active in most countries, detecting early signs of potentially disastrous outbreaks in time for preventative action. These monitoring systems are costly, however, and identifying their economic value requires estimating damages from outbreaks in empirical settings where monitoring is neither uniform nor exogenous. We estimate the value of monitoring systems for the desert locust—known to devour entire agricultural fields—and their impact on human well-being. Our analysis uses data from 1985 to 2020 across Sub-Saharan Africa, the Middle East and South Asia, including locust monitoring records and data from the Demographic and Health Surveys. We leverage conflict and weather events in locust breeding areas to detect the effects of monitoring interruptions on locust swarm outbreaks. We then reconstruct the spatial patterns of locust migrations to propagate these effects on locust swarm outbreaks beyond breeding areas. Finally, we show that in-utero exposure to a locust swarm reduces height-for-age by 0.36 standard deviations and increases the probability of stunting by 7 percentage points (a 16% increase). Taken together, these estimates allow us to quantify the effects of a change in monitoring effort on subsequent locust swarms and on human health. We calculate that in the absence of effective locust monitoring, an additional 238 thousand children per birth cohort in the affected countries would experience stunting, creating economic losses of US$11.9 billion per year. This implies a benefit-cost ratio of over 300 for locust monitoring budgets.

What are the long-term equilibrium impacts of removing apex predators from the environment? We examine how the presence of wolves north, but not south, of the Saint Lawrence River in Canada affects the share of animal-related vehicle collisions. We find evidence that wolves reduce the share of animal-related vehicle collisions by 38.5%—reflecting averted losses valued at 30.7 million 2023 USD. This finding demonstrates that in a setting in which both driver and animal behaviors can be assumed to be in equilibrium, the presence of an apex predator has meaningful benefits to the safety and property of people.

In an attempt to reverse previous local extinction events, several countries have designed programs to reintroduce species, from butterflies to large predators. We evaluate the economic impacts from the reintroduction of wolves, and analyze both the direct effects on livestock and the indirect effects of wolves through their interactions with non-livestock species such as coyotes and deer. We use data on livestock losses, farm income, and vehicle collisions to examine the benefits and costs of reintroducing wolves through their direct and indirect species interactions. Our analysis relies on the quasi-experimental variation from the timing of reintroduction programs that vary by state, and the migration of wolves across administrative borders. We find that wolf recovery does not decrease livestock revenue, productivity, or total losses. Rather, we find that wolf recovery leads to a sharp decrease in predation losses for calves, likely by killing or driving out coyotes. For crops, we find that wolf recovery has no effect on total crop revenue or crop insurance payments, which suggests wolves have little effect on damage caused by deer and other cervids. We find that all-cause vehicle collision rates decline following the reintroduction of wolves, driven mostly by animal-related collisions, but those are strictly concentrated in one out of six states. Our findings make it clear that focusing only on the most obvious direct damages from wolves—as policy debates often do—would yield a miscalculation of net economic losses or benefits, and that spatial heterogeneity is large both for the damages and benefits. This has implications for current and planned wolf reintroduction programs, as well as reintroduction programs for other predator species across the world.

New technologies that deliver large improvements see widespread adoption, even if little is known at the time regarding potential adverse side effects. An example of historical importance is the rapid and widespread adoption of DDT for civilian use after World War II, which ushered an era of high synthetic pesticide use. In the years after its introduction in the US, evidence linking DDT with harmful impacts on wildlife and cancer incidence in humans led to a ban in the US in 1972. Currently, DDT is still used in 24 countries, and there are periodic calls to cancel its ban. In this paper, we use the fact that DDT was predominately used in cotton agriculture in the Southern US as natural experiments that created variation in DDT exposure to test its historical impact on health. We find strong evidence that infant mortality rates (IMR) increased, on average, by 5.5% relative to pre-DDT adoption levels. In further analysis, we demonstrate that these health impacts were concentrated in the non-white population, even when we control for multiple time-varying covariates. These results highlight DDT’s overall negative effect on public health, and that large-scale adoption of new technologies can have negative impacts that are distributed unevenly across the population.

Recent zoonotic disease outbreaks have been traced to wet markets where humans come into close contact with livestock and wild-caught animals. These outbreaks reveal new information about the risks of human-animal interactions. Because previous research has documented both temporary as well as permanent responses to abrupt shocks, it remains unclear how consumers respond following zoonotic disease outbreaks. Here we study the effect of the 2003 SARS epidemic on the live animal trade. Using data on 347,614 import flows for 170 countries, spanning 24 years, we find that SARS initially reduced import demand for live animals by 20% in China, Hong Kong, and Macao (areas that were heavily affected). While the reduction in demand was large, it did not persist, and imports returned to their pre-SARS levels by 2010. These demand dynamics inform ongoing policy discussions on whether regulating wild-caught animal consumption is necessary to prevent future outbreaks.