Ecology

Writing on behalf of participants in a workshop on conservation (see go.nature.com/48sfhkh), we are concerned that you overlook the crucial issue of urban biodiversity when making the case for sustainable cities (Nature 620, 697; 2023).
Competing Interests
The author declares no competing interests. More

World leaders this week vowed to redouble their efforts on an ambitious plan to end poverty and protect the environment, which is woefully behind schedule.None of the United Nations’ 17 Sustainable Development Goals (SDGs), outlined in 2015, will be met by the self-imposed 2030 deadline. Governments and leaders are better at making promises than at keeping them, scientists have told Nature. However, there are signs that the SDG agenda is having an impact, they say.A 12-page “political declaration”, approved during the UN SDG Summit in New York on 18 and 19 September, declares that the goals remain the world’s “overarching roadmap” for the future. “We will act with urgency to realize its vision as a plan of action for people, planet, prosperity, peace and partnership, leaving no one behind,” the agreement states.“The SDGs need a global rescue plan,” UN secretary-general António Guterres declared at the opening of the summit. Guterres is proposing to increase funding for sustainable development by at least US$500 billion to help countries to achieve the goals, as well as other financial aid, including debt relief for the poorest nations so they can survive and thrive after economic shocks.The political declaration arrives amid evidence and analysis suggesting that governments are falling well short of the goals.There is hope for the SDGs yetResearchers involved in the four-yearly Global Sustainable Development Report (GSDR) analysed 36 of the 169 detailed targets that accompany the overarching goals. Of these, the scientists found that the world is on track to achieve only two targets — those aimed at increasing access to the Internet and to mobile-phone networks.Twelve targets showed little or no progress. In some cases, such as food security, vaccine coverage and greenhouse-gas emissions, trends are going in the wrong direction. The research suggests that without further action and resources, the world will be unlikely to achieve the goals even by 2050, two decades late.Paula Caballero, the former Colombian diplomat who was instrumental in creating the SDGs’ framework, says that the world needs to take bold and transformational action now to accomplish the SDG agenda.At the same time, she says that 2030 should not be seen as a final ‘take-it-or-leave-it’ deadline. “Let’s not think that 2030 is an end goal,” says Caballero, who is now responsible for the Latin American activities of The Nature Conservancy, a conservation organization based in the United States. “It’s a milestone.”Sociologist Shirin Malekpour, one of the GSDR authors, agrees. “What needs to change is what we are doing, not the targets and the goals,” says Malekpour, who is at Monash University in Melbourne, Australia.Malekpour sees some hope in the political declaration, which says that countries will not only continue to integrate the SDGs into national policies, but also “develop national plans for transformative and accelerated action”.“If, outside of everything else, they just do this one thing, I think we will actually see huge progress,” she says.Focus on integrated actionFor Caballero, the SDG summit is also evidence that the goals are focusing minds on the integrated nature of the challenges facing humanity. But she says that the UN system is still making the mistake of treating sustainable development and climate as separate issues, including by holding separate SDG and climate summits in New York this week.“The only way you’re going to deliver on climate mitigation and adaptation is through the SDGs, and you can’t meet the SDGs unless you deal with climate,” she says.Although the Paris climate agreement and the SDGs were born of separate political processes in 2015, she says, the two agendas are in fact “one and the same”. More

Chaco Seco is the largest subtropical dry forest in South America. It has many trees, such as Prosopis alba, which bears a nutritious fruit, and Aspidosperma quebracho blanco, which produces a hard wood. The forest has cactus species and Bromelia plants, which are traditionally used to make a textile fibre for clothes and crafts.Project Quimilero is a non-profit group, created in 2015, that aims to protect Chacoan peccaries (Catagonus wagneri), a pig-like animal endemic to Chaco. We work with Indigenous and creole communities to preserve the region’s culture and biodiversity. We meet with the Indigenous Wichí people to record places, animals and plants that are important to them.In this picture from last April, I’m standing near the village of Nueva Población, Argentina, holding a map of the area that was drawn with the help of elder Wichí members. This exchange of knowledge was invaluable for our work. We now understand that the Western concept of ‘territory’, with its rigid boundaries, doesn’t make sense to these communities. Changes in seasons, soil-saturation levels and animal movements force these peoples to go beyond those boundaries to hunt and collect water.When I moved to Chaco in 2010, I realized that deforestation is a major threat to the biodiversity of plants and animals, and to the Indigenous communities. Chacoan peccaries cannot tolerate habitat loss. Our research has predicted they could become extinct in less than 30 years (M. Camino et al. Biodivers. Conserv. 31, 413–432; 2022). Deforestation is due to industrial agriculture and logging. Europe now forbids the import of deforestation products, a policy that could decrease this kind of destruction.More such initiatives are needed. I co-authored a study (M. Camino et al. Glob. Environ. Change 81, 102678; 2023) showing that there is less deforestation in the parts of Chaco Seco that Indigenous communities have the rights to than in other areas. More

Several pieces of legislation that are under consideration in Colombia threaten to change the country’s research landscape if passed, by banning almost all science and education using live animals. Although one bill introduced in Colombia’s Chamber of Representatives has already been rescinded after backlash from scientists, a second bill and a constitutional amendment remain active in the Senate.“Science hasn’t always been supported by politicians in Colombia, but I don’t think any of us saw this coming,” says Nataly Castelblanco-Martínez, an aquatic-mammal biologist at the National Council for Science and Technology in Mexico, who is originally from Colombia and frequently collaborates with scientists back home. “No one is saying we don’t need regulation, but together, [these bills] affect virtually everything we do as researchers.”A rising movementColombia is one of the world’s most biodiverse countries. After a civil conflict that lasted more than 50 years and limited where scientists could travel, researchers resumed chronicling wildlife and establishing conservation plans. But there are many understudied species, and in recent years, an ‘animalist’ movement has developed in Colombia that threatens scientists’ work.
Expeditions in post-war Colombia have found hundreds of new species. But rich ecosystems are now under threat
The bill that has since been withdrawn from the Chamber of Representatives — which hosts a number of politicians who are sympathetic to animal-welfare causes — had stated that “in no case may wild animals be used in education or biological studies”. After scientists raised the alarm, at least four members of the Colombian Congress pulled their signatures. In an e-mail to Nature, the bill’s author, Juan Carlos Lozada Vargas, said that he ultimately withdrew it “to create a space of trust” with scientists. And he has been visiting researchers in various institutions since then.Some scientists say that ‘animalists’ are taking advantage of the closure earlier this year of a malaria research facility in Cali, which had been funded by the US National Institutes of Health, to push through more restrictive animal-research policies. The animal-welfare organization People for the Ethical Treatment of Animals (PETA) unearthed evidence of alleged animal abuse at the laboratory.At the same time, there’s an ongoing debate over how best to manage a population of invasive hippos accidentally introduced into Colombia after they escaped from the drug-cartel leader Pablo Escobar’s estate outside Medellín. The hippos, biologists say, threaten native species, and their population must be reduced. Others, however, are protective of the hippos and the benefits they bring through tourism. The Animal Legal Defense Fund, an organization that advocates for the rights of animals, filed a lawsuit against the government over its efforts to control the hippos, and Colombian senator Andrea Padilla Villarraga recently introduced a draft constitutional amendment that would recognize animals as people, with commensurate legal protections.Researchers note that granting personhood to something like an invasive species would be a dangerous precedent that ignores the damage a single species can do to an entire ecosystem. In an e-mail to Nature, Padilla Villarraga rejected this argument. “Does environmental protection conflict with the protection we owe to other animals as sentient individuals?” she asked. “It is a false dilemma to think that you have to choose between one and the other.”Research transformedPadilla Villarraga is also the author of the pending Senate bill that would curtail animal research and overhaul the country’s ethical-approval process. The bill states that “the use of live animals in academic and scientific research, toxicity-testing studies, biological or related studies” is prohibited when the results can be obtained “by other means” or when using “live animals of a higher grade on the zoological scale”. Scientists say that they take this to mean animals with greater cognitive capacity or sentience, but that the vagueness of the bill makes it challenging to interpret.

Carlos Daniel Cadena Ordoñez handles a white-breasted wood wren (Henicorhina leucosticta) captured for research purposes using a mist net.Credit: Guillermo Gómez

Carlos Daniel Cadena Ordoñez, the dean of the school of science at the University of the Andes in Bogotá, says that larger institutions in cities might be able to meet these new requirements, but that smaller, more rural ones probably won’t. “There are all these barriers to science, and now we’re going to put more barriers that are going to make it even more exclusionary,” he says.
Landmark Colombian bird study repeated to right colonial-era wrongs
Beyond the damage that the legislation would do to research, it would change the way in which students are educated. The bill states that undergraduate students cannot interact with animals until their last two years at university, and then only under supervision. “But all the research that I do, I do with students,” says Andrés Cuervo, an ornithologist at the National University of Colombia in Bogotá, who focuses on avian biodiversity. “We need to put these people out there in the field right away.”The Senate bill would also effectively shutter the conservation work of Ana María Morales, a wildlife biologist at the Eagles of the Andes Foundation, a bird-rehabilitation centre in Pereira. She observes endangered black-and-chestnut eagles (Spizaetus isidori), and sometimes captures and tags them. Animals that cannot be released are used to educate the public and to train professionals on proper handling techniques. “As the only raptor rehabilitation centre in Colombia, we are the ones that have this information, and this bill will prevent us from sharing it,” she says.A tense waitThe likelihood of the bill passing remains unclear. Cuervo says that it has a good chance of making its way to President Gustavo Petro, and that it could be signed by the end of the year. But others, including Cadena Ordoñez, think it’s unlikely to pass, given the reaction to the withdrawn Chamber of Representatives bill. However, “we have to act as though it will, because a lot of people will be out of work if this bill goes through,” he says.The threat has prompted Colombian scientists to organize. What began as a WhatsApp chat among concerned biologists has grown into a group called Biodiversos that currently has more than 2,750 members. Castelblanco-Martínez, who is a member, says that the group has been largely reactive — putting out statements in opposition to the bills — but that is changing: members recently attended a forum with Padilla Villarraga to outline their concerns. “The fact that we’re coming together, all working towards the conservation of our resources, it’s really great,” she says. More

Observations of birds are relatively scarce in neighbourhoods that were redlined, or designated as risky for mortgage lending, in the 1930s.Credit: George Rose/Getty

Ecologist Diego Ellis-Soto has plenty of local bird data to study. On the university campus where he works, more than half a million bird sightings have been recorded over the past century. But Dixwell, a neighbourhood just down the road, has totalled just a few dozen bird observations in the same period.“I could go there one day and double what’s been collected in the last 100 years,” says Ellis-Soto, who’s at Yale University in New Haven, Connecticut. It might be no coincidence that Yale’s students and faculty are mostly white — in contrast to Dixwell, which has a high proportion of residents who are Black.The disparity in recorded bird sightings doesn’t affect just New Haven. An analysis1 by Ellis-Soto and his colleagues shows that data on bird biodiversity are scarcest in US neighbourhoods, such as Dixwell, that have historically been subjected to certain racially discriminatory policies. This lack of information could affect scientists’ understanding of how birds are distributed in US cities and how species fare over time.Red zones for real estateIn the 1930s, a US-government-led effort graded urban neighbourhoods across the country on whether they were ‘safe’ for real-estate investment. Areas that were judged to be the safest bets for investment were rated ‘green’, and those judged to be highest risk were rated ‘red’. Grades were determined, in part, by a neighbourhood’s racial composition. This categorization, now called redlining, drove investment in wealthier and white neighbourhoods. It also led to a lack of investment in poorer areas and in neighbourhoods of colour.
Landmark Colombian bird study repeated to right colonial-era wrongs
To study how redlining has affected biodiversity assessment, Ellis-Soto and his team studied bird sightings in more than 9,000 neighbourhoods, covering almost 200 US cities. They found that there were many more bird observations per square kilometre in green districts, whose residents are in many cases still predominantly white, than in redlined districts, whose residents are mainly people of colour.“You can better predict where you have data on birds based on systemic racism — redlining maps from 1933 — than climate, tree cover or population density, everything a bird should actually care about,” Ellis-Soto says.From 2000 to 2020, the density of bird observations rose steeply in green neighbourhoods, but more gradually in red ones. The disparity in observations between green and red zones grew by more than 35% in that period, the authors calculate.The study is one of the first direct looks at how “systemic racism can play a role in the ecological process”, says Jin Bai, an urban ornithologist at North Carolina State University in Raleigh.Missing data, missing fundsData on biodiversity constitute the “first building block” for distributing funds to protect wildlife, says Ellis-Soto. Without data to show their ecological importance, redlined areas could be passed over for funding — widening historical inequalities.“It’s essentially this self-perpetuating negative loop,” says Chris Schell, an urban ecologist at the University of California, Berkeley. “You have more observations of a native species in an environment that already has a ton of money. Then that same neighbourhood gets more money to conserve a species, which makes it more exclusive, which makes housing more exclusive, which then continues the legacies of segregation.”Ellis-Soto says the gap in data is due, in part, to biases held by scientists and birders, who tend to survey the same areas repeatedly. A lack of resources for teaching birding and for recording observations in historically marginalized areas also contributes.Ellis-Soto would like federal funding for such education efforts. But in the meantime, he takes Black and Hispanic kids from New Haven for nature walks and teaches them how to log the birds they see. “That’s my little solution,” he says. More

Humanity and some of the world’s most charismatic wildlife are on a collision course in the oceans.The world’s merchant fleet — from oil tankers to bulk cargo carriers and container ships — has doubled in size in just 16 years to more than 100,000 vessels, according to United Nations figures (see ‘A fast-growing fleet’). Between 2014 and 2050, shipping traffic is expected to rise by up to 1,200%1.These numbers, combined with data on where shipping networks overlap with the movements and aggregations of marine animals2,3, together with assessments of the effects of ship strikes on certain marine species, present an increasingly alarming picture. They suggest that ship strikes could be helping to drive the population decline of many animals, leading to profound effects throughout their ecosystems, for instance by altering biogeochemical fluxes4.

Source: UNCTAD

Yet compared with other threats to marine biodiversity, such as climate change and pollution, the problem of ship strikes harming wildlife is tractable. Various technologies and approaches are increasingly enabling surveillance of both ships and wildlife. Global regulation of the shipping industry has already been established to limit greenhouse-gas emissions. And various schemes to reduce strikes have proved effective in some locations for certain species.What’s needed now are four changes. First, researchers require better data on where, when, how often and for which species strikes are occurring. Second, there must be greater engagement with the problem, both from the shipping industry and the public. Third, regulations should be brought in to either reduce ship speed in certain areas or reroute vessels; and finally, there must be monitoring of adherence to such restrictions. With these changes, there is no reason why this problem cannot be addressed.Tip of the icebergCollisions between ships and ocean animals are hard to quantify because they are not systematically recorded, and can go unnoticed when large vessels are involved. Carcasses can sink before they are observed.Numerous lethal strikes have been documented worldwide in the past 100 years or so, often by scientists using eyewitness accounts or by direct observations of floating, dead animals2,3. Researchers have been warning of the impacts of global shipping on whales for nearly two decades5. And for some species, research has established the importance of ship strikes relative to other threats. A 2019 study, for instance, showed that, alongside entanglement in fishing gear, ship strikes are a leading cause of human-induced mortality for the critically endangered North Atlantic right whale (Eubalaena glacialis)6.

An acoustic monitoring buoy.Credit: Woods Hole Oceanographic Institution

By collating information dating back to 1877 on what species have been struck by vessels, a 2020 study identified more than 75 marine species as being at risk of harm from strikes2. The marine megafauna — whales, sharks, sea turtles and other organisms with a body mass of 45 kilograms or more — top the list. These ocean giants spend most of their lives at the surface3, travel hundreds or thousands of kilometres across ocean basins and often aggregate in coastal and continental-shelf areas7.The list includes some of the most endangered animals: 60 are on the International Union for Conservation of Nature’s Red List of Threatened Species2. More than one-third of those listed are threatened with extinction. For the other 15, there are insufficient data to make an assessment.
UN high seas treaty is a landmark – but science needs to fill the gap
Studies on ship strikes so far, however, are not comprehensive and have drawn on data collected only from particular areas and only for some species. According to conservative estimates based on deaths of three whale species in four US study sites, for example, ships kill more than 80 whales a year in an area measuring roughly 800,000 square kilometres8. Yet for other species, data on the number of deaths and the location of collisions are missing. Reports of strikes tend to focus on a few species that are most likely to be seen floating when dead, such as whales, dolphins and turtles. But the majority of marine animals, and all cartilaginous fishes (sharks, rays, skates and so on), sink when dead and so will not be observed2.A 2022 study co-authored by two of us (F.C.W. and D.W.S.) attempted to assess the global impact of collisions on whale sharks (Rhincodon typus), a species that sinks quickly when dead3. The findings are concerning. Satellite data that tracked the relative positions of whale sharks and vessels show that 92% of the species’ use of horizontal space and nearly 50% of its vertical space use overlaps with shipping routes. Strikes could explain why the population is continuing to decline even though mortality caused by fishing has been reduced.In short, various lines of evidence indicate that existing records of ship strikes — and the estimates made so far of the impact of collisions on marine life — represent the tip of the iceberg for current and future harms of the shipping industry to marine biodiversity.Data on demandFortunately, the tools and key players needed to collect and analyse data across ecosystems and jurisdictional borders — and to develop mitigation strategies — already exist.Various international projects are already collating and distributing data on where animals are and how they move through the ocean. These include platforms that rely on surveys, such as the Ocean Biodiversity Information System; animal-tracking databases such as Movebank; and tools that predict animal distributions on the basis of sightings and assessments of habitat suitability, such as AquaMaps.Likewise, shipping information can be obtained from providers of Automatic Identification System data, which use satellites to track vessels, as well as from ocean-monitoring initiatives such as Global Fishing Watch and from the US National Oceanic and Atmospheric Administration (NOAA).

A shortfin mako shark (Isurus oxyrinchus) with satellite tags in the Pacific Ocean.Credit: Mark Conlin/Alamy

Using such data, whale experts and other researchers have already started to pinpoint high-risk areas2,3 (see Supplementary information). Our work on whale sharks showed that one is the Strait of Hormuz between the United Arab Emirates and Iran, through which about one-third of global maritime-traded oil passes each year (see go.nature.com/47kjric).For many species, this information is not yet available. Also, data collection is often patchy and disparate, with animals being tracked only in part of their range, and various data-gathering approaches being used in different areas.Governments, industry and philanthropic and other organizations can help to fill the gaps by bolstering pre-existing projects. Various mobile-phone app and web-based initiatives are leading the way with technology-powered mapping and analysis. For instance, the Whale Safe tool uses various measures, including public whale sightings, to help establish voluntary speed restrictions and other actions to reduce the risk of strikes. The use of low-Earth-orbit satellites to monitor large marine animals from space — currently an untapped technique — could provide researchers and other stakeholders with near-real-time, actionable data for high-risk areas9.But efforts must be scaled up, with those involved in local and regional projects facilitating the establishment of similar initiatives in other parts of the world, particularly in the global south. Existing efforts to connect projects and partners associated with the ocean will be key. Since 2021, for instance, the United Nations Decade of Ocean Science for Sustainable Development programme has been connecting people and organizations concerned with the role of kelp forests and seagrass beds in storing carbon, among many other issues.Increased engagementIn the past few years, it has become increasingly common for commercial shipping companies to disclose their environmental, social and governance goals in publicly available sustainability reports. Although nine of the ten largest shipping companies address whale strikes as an area of concern in their reports, the degree to which companies take action on this issue varies widely. Also, to our knowledge, none of these sustainability reports explicitly mentions megafauna other than whales.In 2007, the International Whaling Commission launched a long-term initiative to collect and analyse information about reported whale strikes: the Global Ship Strikes Database. With greater engagement from shipping companies, port authorities and industry partners, a centralized database of strikes could be built for all affected species. As well as protecting marine wildlife by helping ships to avoid collisions, such a database could bolster companies’ reputations in an increasingly eco-conscious world, and lessen disruptions to shipping operations.

Hong Kong’s container terminal is one of the largest in the world.Credit: xPACIFICA/Redux/eyevine

Currently, the International Convention for the Safety of Life at Sea (SOLAS), a treaty that ensures ships registered by signatory states comply with minimum safety standards, requires that all ships engaged in international voyages keep an on-board record of navigational activities and incidents relevant to safety. Adding wildlife collisions and near misses to this reporting could enable information to be collected in a comprehensive ship-strikes database. Another measure could require particular ships to have marine megafauna observers on board. (This already happens on vessels conducting seismic surveys, for example, to ensure that the noise from underwater soundings is minimized when whales are nearby.) On the rare occasions on which animals remain lodged on a ship’s bow, strikes could even be recorded by port authorities.
What whale falls can teach us about biodiversity and climate change
Ways to record ship strikes without direct human involvement are being developed, including forward-facing and thermal-imaging cameras, infrared and thermal sensors and underwater echo sounders to image animals. Technology developed by the Woods Hole Oceanographic Institution in Massachusetts uses a camera the size of a shoebox and an artificial-intelligence (AI) algorithm to help ships detect and avoid whales10. (The algorithm is trained to identify whether a whale is present; if so, the program sends a signal to the ship’s operator so they can slow down or change course.) Also, the shipping industry is increasingly using advanced autopilot systems based on AI and deep learning11. In principle, hazard-detection systems on autonomous vessels could be trained to identify marine megafauna, log incidents and implement any necessary evasive manoeuvres.Conventions and treaties that are already in place to increase industry and public engagement in ocean-environment issues could help with all this. But instruments such as the Biodiversity Beyond National Jurisdiction treaty (a framework adopted earlier this year to tackle biodiversity loss on the high seas) must explicitly address the issue of ship strikes. Currently, there is no mention of this in the treaty.Shipping regulationsThe best way to reduce strikes is to separate ships from wildlife. The International Maritime Organization (IMO) is a specialized UN agency responsible for worldwide shipping regulations. Through SOLAS, the IMO can reroute ship traffic to avoid collisions with a floating object or to ensure that areas crucial for some species’ feeding or reproduction at particular times of year are avoided.Permanent or seasonal traffic diversions around wildlife areas have proved hugely effective2. For whales, even minor routing changes in high-risk areas have led to substantial reductions in strikes. For instance, in the Bay of Fundy off Canada, moving a shipping route eastwards by just 4 nautical miles (7.4 km) in 2003 reduced the risk of vessels colliding with North Atlantic right whales by 90%12.

A whale shark (Rhincodon typus) thought to have been scarred in a collision with a vessel.Credit: Claudio Contreras/Nature Picture Library

Several studies and reports show that, in places where ships cannot be rerouted, speed reductions can lower the risk and the lethality of a strike2. In 2008, voluntary and mandatory speed limits of 10 knots (18.5 km per hour) were applied in certain areas along the US east coast. In the first 5 years after implementation, there were no records of ships striking North Atlantic right whales either inside or within 45 nautical miles of these areas13. Studies incorporating emissions show that speed restrictions can bring other benefits. In a 2019 study, decreasing speeds by as little as 10% lowered the risk of ships striking whales by 50%, reduced underwater noise by 40% and cut greenhouse-gas emissions by 13%14.Despite the evidence that rerouting and speed reductions mitigate ‘ocean roadkill’, restrictions on ship routes and speeds remain disparate and uncoordinated, just like data collection on marine animals. A global, IMO-mediated treaty mandating maximum average speeds — and rerouting to ensure ships avoid areas of high collision risk — could be one of the easiest ways to protect wildlife from ship strikes. In fact, regulations introduced this year to ameliorate the effects of climate change from shipping, such as the IMO 2023 Energy Efficiency Existing Ship Index and the Carbon Intensity Indicator, already stipulate lower speeds for certain vessels.A cloud-based, open-data portal could facilitate the establishment of up-to-date, dynamic policies by integrating data on animal and ship movements, risk maps, geo-referenced strike reports, current spatial protections and relevant maritime features into a single mapping resource. This would be similar to HUBOcean, which brings diverse data sources together on one platform to enable scientific collaboration, industry transparency and regulation. Crucially, data could be made available to all stakeholders, from government agencies and non-governmental organizations to academic researchers and industry partners.Monitoring adherenceOnce regulatory changes have been relayed to industry, adherence to speed and route restrictions could be monitored at a national level using data from Automatic Identification Systems. Ship owners, shipping companies and port authorities could also help to ensure regulatory compliance. Financial penalties could be used to discourage speeding or encroachment in no-go zones. In principle, subsidies, tax breaks and other forms of governmental financial support aimed at environmental objectives could be used to reduce ship strikes on marine megafauna.Because governments are unlikely to act without sufficient public pressure, a global ‘wildlife-safe’ shipping eco-certification scheme could be crucial. Similar to NOAA’s ‘dolphin-safe’ tuna-can labels — which aim to signal compliance with US laws and regulations around tuna fishing operations — this would help to increase consumer awareness of the problem and enable informed choices. Scaling up the success of voluntary certification programmes, such as Friend of the Sea’s Whale-Safe label, alongside its certification of seafood from sustainable fisheries and aquaculture, would greatly increase the visibility of this issue.Loss of the ocean’s largest animals will have major unforeseen consequences for the health of the seas. Making ship strikes a higher priority globally is one immediately achievable way to help to conserve the world’s most vulnerable and iconic marine species. More

Oceans are warming up, and dangerously so. Since April this year, the average global sea surface temperature has been unusually high and rising; by August, oceans in the Northern Hemisphere had reached record-high temperatures, even surpassing 38 °C in one area around Florida.These extreme temperatures, fuelled by the climate crisis, have manifested as a series of marine heatwaves — periods of anomalously warm sea temperatures that can last for weeks, months or even years — across the Northern and Southern hemispheres. In some areas around the United Kingdom and Ireland, for example, surface waters in June and July were 4–5 °C warmer than is usually recorded at this time of year. Temperatures are also soaring off the coast of Florida and into the Gulf of Mexico, extending across the tropical Pacific, around Japan, and off the coasts of Ecuador and Peru. Marine heatwaves are more intense, last longer and occur more frequently than they used to. From 1925 to 2016, the number of days classed as experiencing marine heatwaves increased by 54%1.This makes the concurrent likelihood of a strong El Niño — a climate phenomenon that is typically associated with a rise in global temperatures — particularly worrying.Marine heatwaves disrupt, threaten and damage ecosystems. They are particularly dangerous for temperature-sensitive organisms that live in cool waters, such as kelps, and immobile warm-water organisms, such as corals. Many species might be susceptible to disease or mortality, with knock-on effects. For example, in 2014–15, a marine heatwave off the west coast of the United States, dubbed the Blob, caused widespread loss of sea stars. This in turn caused a bloom of sea urchins (on which sea stars predate), which in turn damaged kelp forests2. Rising water temperatures can also cause some species to migrate to cooler waters.Such events also affect local communities, including through economic losses from impacts on fisheries and aquaculture. The Peruvian anchoveta (Engraulis ringens), for example, disappears from its usual fishing grounds during marine heatwaves. In 2015–16, the sea off eastern Tasmania in Australia saw high mortality rates for oysters and abalones during a warm spell. And although tourism has played a part in the degradation of corals, mass bleaching of coral reefs also dents tourism, because white corals do not appeal to snorkellers and divers. The impact of a heatwave on marine industries can run into billions of dollars3.

An autonomous glider is deployed into the Indian Ocean to monitor marine conditions.Credit: Suzanne Long/Alamy

Given the impending overlap of El Niño conditions with long-term warming trends, it is pressing to closely monitor regions with a high likelihood of marine heatwaves, and to develop and implement a range of approaches for reducing risks to wildlife and economies. Here, we urge decision makers in marine and coastal biodiversity conservation, fishing, aquaculture and tourism industries to devise such a strategy for the coming months as well as for the decades ahead. We set out four priorities.Identify threatened regionsWhere communities are prepared, impacts can be mitigated, at least partially. This depends on knowing which regions are most likely to be affected.An analysis of historical data can reveal which areas experienced marine heatwaves during previous El Niños, and suggests where such events are most likely to occur when it develops: in the northeast Pacific (affecting coastal waters from California to the eastern Bering Sea); the tropical central-to-eastern Pacific and the shelf waters of Ecuador and Peru; off eastern Australia; and the Indian Ocean, including off the east coast of Africa, southern India, and southeast Asia (see ‘El Niño and marine heatwaves’ and Supplementary information). These areas are known to be susceptible to mass die-offs of diverse marine habitats, from tropical coral reefs to temperate kelp forests4.

Source: Analysis by A. J. Hobday et al. based on data from marine.copernicus.eu; see Supplementary Information

El Niño occurs as part of a cycle (see ‘What is El Nino?’), but this is not the only climate cycle to influence marine heatwaves. Other ocean and atmospheric patterns operate on timescales ranging from a few years to several decades. These manifest as natural variations in temperature in different ocean basins5. For instance, the current negative phase of the Pacific Decadal Oscillation is associated with warming waters around Australia, the northwest Pacific, the northern Indian Ocean and parts of the South Pacific and South Atlantic. In the next few months, a positive Indian Ocean Dipole is also predicted to start to warm the western Indian Ocean. This pattern, reinforced by El Niño,typically brings a warm and dry summer for many parts of Australia.
What is El Niño?

Short-term patterns in global climate such as El Niño are superimposed on long-term anthropogenic warming, with serious consequences predicted for many regions of the globe.
The El Niño–Southern Oscillation is a major climate phenomenon that comprises a warm phase (El Niño), a cool phase (La Niña) and a neutral phase. These switch, irregularly, every few years. El Niño — when winds over the tropical Pacific falter and the warmest waters in the western Pacific flood eastwards, disrupting the entire atmospheric circulation — has the most widespread impact on sea surface temperatures globally.
For the past three years, the world has been experiencing La Niña conditions, associated with cooler global temperatures and cooler-than-average sea surface temperatures in the central and eastern tropical Pacific. Earlier in 2023, conditions in the tropical Pacific began to reverse and El Niño seems to be developing. It is likely to amplify until the end of this year and possibly into next year as well, and is poised to trigger major marine heatwaves.

There are counter trends, too — although El Niño drives rising temperatures in many areas, it suppresses the likelihood of marine heatwaves in a few regions, including the waters off Papua New Guinea, New Zealand, the Philippines and western Australia.Although our understanding of marine heatwaves has lagged behind that of their atmospheric counterparts, researchers have learnt a great deal about these extreme events since the last El Niño. A better grasp of how different climate cycles are connected, as well as their influences, will aid preparations.Improve forecasts and warningsWork is progressing on predicting spikes in seawater temperatures6. Ocean weather forecasts are reliable a week or so in advance7, probabilistic seasonal forecasts give indications several months ahead8,9, and centennial-scale climate projections that take into account anthropogenic greenhouse-gas emissions provide the longest view10.Spatial maps showing probabilities of marine heatwaves are most accurate in open oceans where climate drivers, particularly El Niño, are strongest, and less so nearer coasts, where local ocean and atmospheric conditions become important. Building predictive power for these regions — by improving coupled ocean–atmosphere models and assessing the accuracy of their predictions — is crucial for local biodiversity conservation efforts as well as the fishing, aquaculture and tourism industries.Plan local responsesThis year, countries such as Australia and the United States are using seasonal-scale early warning systems, with lead times of several months, to provide marine-heatwave briefings to conservation agencies, the fishing and aquaculture industries, and the public.Options to alleviate potential impacts or improve recovery after a marine heatwave vary by industry (see ‘Managing marine heatwaves’ and Table S1 in Supplementary information). These steps depend on the marine environment and the species or ecosystems of concern, as well as on the expected timing, severity and spatial extent of the forecast event.

Source: Adapted from A. J. Hobday et al. Prog. Oceanogr. 141, 227–238 (2016) and https://go.nature.com/45UXWBP

In the case of marine heatwaves predicted to develop in winter and spring, when waters are generally coolest, aquaculture industries might need to change the feed mix for species such as salmon, prepare for disease outbreaks, or change the time of harvest to ensure animals are in prime condition. For summer and autumn events, when temperatures exceed the coping range for many species, fisheries might need to reduce catch limits or close an area altogether, to enable species to cope with the stress of warmer waters. Without such interventions, marine heatwaves can result in reduced catches for several years, as was seen in crab and scallop fisheries off western Australia following a 2011 event.Changes in the distributions of species could also challenge jurisdictional management for fisheries. For example, when mackerel and squid moved from southern to northern Californian waters in 2016, quota management, employment and market prices were affected.

A kelp forest near Santa Barbara Island, California.Credit: David Fleetham/Nature Picture Library

The fishing and aquaculture sectors can shift harvesting and production schedules to maximize yield before temperatures rise, move inactive fishing vessels to cheaper moorings and reduce seasonal staff hiring in regions where activities are poised to decline. Other management strategies might include delaying restoration of kelp and seagrass in previously affected areas when further marine heatwaves are forecast. Innovative approaches, such as restoration that introduces species adapted to warmer conditions or the temporary alteration of clouds to protect coral reefs from solar radiation, need to be investigated.Some tourism enterprises, such as diving or snorkelling firms, might reduce numbers of staff during marine heatwaves, or modify their activities to minimize job losses. Whale-watching trips could be increased, for example, as happened off the coast of San Diego, California, during the Blob. Sports-fishing companies should ensure they have the appropriate permissions, equipment and staffing when warmer-water species move to areas where they are not usually seen.Monitor impacts of warmer watersFor the scientific community, warnings months ahead of likely rises in temperatures provide the opportunity for in-depth studies. Hypotheses can be developed and tested, data can be gathered — for example, by using underwater gliders to determine the vertical structure of heatwaves — and samples can be collected and analysed.

A sunflower sea star (Pycnopodia helianthoides; right) and red sea urchins (Strongylocentrotus franciscanus) off southeast Alaska.Credit: Jeff Mondragon/Alamy

To better understand ecological responses to extreme warming events, researchers should scale up monitoring efforts to characterize a region’s physical and biological conditions before a heatwave’s onset. They should deploy sensors to measure key variables (such as temperature, oxygen levels, salinity, and the abundance and composition of nutrients and plankton) across multiple scales in time and space and at high resolution, from the surface to deeper waters. Although intense sampling during an extreme event provides a wealth of information, robust characterization of an ecosystem before a heatwave is also crucial, to provide a baseline. Data should be collected to assess changes in habitat types as well as the growth, reproduction and survival of species.A wide range of approaches, including remote sensing (such as for monitoring phytoplankton), fisheries surveys (to assess changes in fish distribution and abundance, for example), environmental DNA collection and citizen science (for detecting species outside their normal ranges) can help. Indigenous and local communities might notice early changes in the environment and should lead monitoring and planning endeavours.Predictions of which species or habitats will be affected by a marine heatwave, on the basis of existing information or ecological theories, will allow hypotheses to be tested — such as the idea that impacts are greatest in the warm part of a species’ range. Species that can survive only in a narrow range of temperatures, such as tropical corals, and those living close to their thermal limits, can serve as indicator species for wider impacts.

A green sea turtle (Chelonia mydas) swims near an algal bloom off Tenerife in the Canary Islands.Credit: Sergio Hanquet/Nature Picture Library

Oceanographic survey tools such as gliders and autonomous underwater vehicles should be deployed to sample the evolution of marine heatwaves. They can record a range of data, including on temperature and salinity but also levels of ocean acidification and of oxygen and nitrogen, to better understand environmental change. Where threatened species or populations might be affected, being able to collect and ‘biobank’ samples to preserve genetic diversity would be an important step for further research and subsequent restoration.Worryingly, the climate crisis could eventually cause oceans to reach a permanent heatwave state relative to historical baselines11, and some regions might no longer support certain species and ecosystems. The ecosystems that emerge might not operate and respond to warmer waters in ways that can be anticipated12. Scientists might not be able to prevent these consequences, but it is crucial to devise and implement adaptive strategies to keep them at bay temporarily or soften their impacts wherever possible. This could buy time for species and ecosystems, and the industries that rely on them, to adjust and transform9.Regardless of whether a full-blown El Niño event occurs this year, these preparations will aid many marine businesses, because all projections indicate that more-frequent, stronger and longer-lasting marine heatwaves are inevitable in the near future. More

Freshwater biodiversity in China’s upper Yellow River is once again under threat, this time from the planned Heishan Gorge hydraulic engineering project. This follows the construction of multiple reservoirs along the Yellow River basin since the 1950s. Local governments should learn from the past and assess the project’s potential ecological impacts before going ahead.
Competing Interests
The author declares no competing interests. More