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By Kaitlyn Gaynor, PhD Candidate

For their first 100 million years on planet Earth, our mammal ancestors relied on the cover of darkness to escape their dinosaur predators and competitors. Only after the meteor-induced mass extinction of dinosaurs 66 million years ago could these nocturnal mammals explore the many wondrous opportunities available in the light of day.

Fast forward to the present, and the honeymoon in the sun may be over for mammals. They’re increasingly returning to the protection of night to avoid the Earth’s current terrifying super-predator: Homo sapiens.

My colleagues and I have made the first effort to measure the global effects of human disturbance on the daily activity patterns of wildlife. In our new study in the journal Science, we documented a powerful and widespread process by which mammals alter their behavior alongside people: Human disturbance is creating a more nocturnal natural world.

Many catastrophic effects of humans on wildlife communities have been well-documented: We are responsible for habitat destruction and overexploitation that have imperiled animal populations around the world. However, just our presence alone can have important behavioral impacts on wildlife, even if these effects aren’t immediately apparent or easy to quantify. Many animals fear humans: We can be large, noisy, novel and dangerous. Animals often go out of their way to avoid encountering us. But it’s becoming more and more challenging for wildlife to seek out human-free spaces, as the human population grows and our footprint expands across the planet.

Global increase in nocturnality

My collaborators and I noticed a striking pattern in some of our own data from research in Tanzania, Nepal and Canada: animals from impala to tigers to grizzly bears seemed to be more active at night when they were around people. Once the idea was on our radar, we began to see it throughout the published scientific literature.

It appeared to be a common global phenomenon; we set out to see just how widespread this effect was. Might animals all over the world be adjusting their daily activity patterns to avoid humans in time, given that it is becoming harder to avoid us in space?

To explore this question, we conducted a meta-analysis, or a study of studies. We systematically scoured the published literature for peer-reviewed journal articles, reports and theses that documented the 24-hour activity patterns of large mammals. We focused on mammals because their need for plenty of space often brings them into contact with humans, and they possess traits that allow for some flexibility in their activity.

We needed to find examples that provided data for areas or seasons of low human disturbance – that is, more natural conditions – and high human disturbance. For example, studies compared deer activity in and out of the hunting season, grizzly bear activity in areas with and without hiking, and elephant activity inside protected areas and outside among rural settlement.

Based on reported data from remote camera traps, radio collars or observations, we determined each species’ nocturnality, which we defined as the percentage of the animal’s total activity that occurred between sunset and sunrise. We then quantified the difference in nocturnality between low and high disturbance to understand how animals changed their activity patterns in response to people.

Overall, for the 62 species in our study, mammals were 1.36 times as nocturnal in response to human disturbance. An animal that naturally split its activity evenly between the day and night, for example, would increase its nighttime activity to 68 percent around people.

While we expected to find a trend toward increased wildlife nocturnality around people, we were surprised by the consistency of the results around the world. Eighty-three percent of the case studies we examined showed some increase in nocturnal activity in response to disturbance. Our finding was consistent across species, continents and habitat types. Antelope on the savanna of Zimbabwe, tapir in the Ecuadorian rainforests, bobcats in the American southwest deserts – all seemed to be doing what they could to shift their activity to the cover of darkness.

Perhaps most surprisingly, the pattern also held across different types of human disturbance, including activities such as hunting, hiking, mountain biking, and infrastructure such as roads, residential settlement and agriculture. Animals responded strongly to all activities, regardless of whether people actually posed a direct threat. It seems human presence alone is enough to disrupt their natural patterns of behavior. People may think our outdoor recreation leaves no trace, but our mere presence can have lasting consequences.

Future of human-wildlife coexistence

We don’t yet understand the consequences of this dramatic behavioral shift for individual animals or populations. Over millions of years, many of the animals included in our study have evolved adaptations to living in the daylight.

Sun bears, for example, are typically diurnal and sun-loving creatures; in undisturbed areas less than 20 percent of their activity occurred at the night. But they increased their nocturnality to 90 percent in areas of the Sumatran forest where intensive forest research activity created a disturbance.

Such diurnally adapted animals may not be as successful at finding food, avoiding predators or communicating in the darkness, which could even reduce their survival or reproduction.

However, because our mammalian ancestors evolved under the cover of darkness in the time of the dinosaurs, most mammal species possess traits that allow for some flexibility in their activity patterns. As long as animals are able to meet their needs during the night, they may actually thrive in human-dominated landscapes by avoiding daytime direct encounters with people that could potentially be dangerous for both parties. In Nepal, for example, tigers and people share the exact same trails in the forest at different times of day, reducing direct conflict between humans and these large carnivores. Dividing up the day, through what researchers call temporal partitioning, may be a mechanism by which people and wildlife can coexist on an ever more crowded planet.

An increase in nocturnality among certain species may also have far-reaching consequences for ecosystems, reshaping species interactions and cascading through food webs. In California’s Santa Cruz Mountains, coyotes are becoming more nocturnal in areas with human recreation. By analyzing coyote scat, scientists have linked this behavioral change to dietary shifts from diurnal to nocturnal prey, with implications for small mammal communities and for competition with other predators.

Working on this study reminded me that people aren’t alone on the planet. Even if we don’t see large mammals while we’re out and about during the day, they may still be living alongside us, asleep while we are awake and vice versa. In areas where threatened species live, managers may consider restricting human activity to certain times of the day, leaving some daylight just for wildlife.

And it is likely that we need to preserve wilderness areas entirely free of human disturbance to conserve the most vulnerable and sensitive mammal species. Not all animals are willing or able to just switch to a nocturnal lifestyle around people. Those that try to avoid human disturbance entirely may be most vulnerable to the consequences of the expanding human footprint.

Kaitlyn Gaynor, Ph.D. Candidate in Environmental Science, Policy and Management, University of California, Berkeley

This article was originally published on The Conversation. Read the original article.

Check out more coverage on this study covered in The Atlantic, Outside Magazine, Scientific American, LA Times, The Guardian

By Lauren Withey, PhD Candidate

At the end of May, Colombia will hold the first round of Presidential Elections to decide the heir to the challenges of implementing the peace accord current President Juan Manuel Santos reached with the FARC guerillas in 2016. The accord was finalized in the end of 2016, but the hiccups and dramas of the four-year negotiations and ratification have continued through the implementation phase. The current government is trying to realize their commitments in a time of financial strain – with oil prices down, government coffers are depleted, leading to budget cuts that would seem to possibly undermine some of the priorities of the peace deal, particularly in the realm of the environment. The country’s 2018 budget for the environment and sustainable development is down 8.8 percent from the year before.

This dip in funding is unfortunate, especially as there has been much talk of the possibilities of “green” development for Colombia in the post-accord phase: a less extractive-intensive economy aligns well with the spirit of the accord, and there is an expansive opportunity for Colombia to cash-in on its stunning and varied landscapes via ecotourism, an industry long stifled by the conflict. The country has been quick to sign onto international commitments and ambitious goals to reduce deforestation, but reaching these targets hasn’t gotten any easier, as the end of the conflict has seen an uptick in deforestation rates – up 44 percent in 2016 over the previous year. This surprised few, given the role the FARC played in strategically maintaining forest cover in the many forested parts of the country it controlled.

the end of the conflict has seen an uptick in deforestation rates – up 44 percent in 2016 over the previous year

These challenges have provoked great interest on the part of international organizations to fill this funding gap by supporting Colombia in its efforts to maintain forest cover, primarily toward climate change mitigation ends. Colombia’s government has received funding from various bilateral donors (Germany, Norway, and the UK, among others) and multilateral donors (including via multiple programs of the World Bank and the United Nations) to fight deforestation. Much of this ~308 million USD has come in specifically to support the UNFCCC¹ program known as REDD+ (Reduced Emissions from Deforestation and Degradation “Plus”), which is meant to reduce deforestation and thereby its threats to climate change by paying states and communities for their reductions in deforestation rates.

Most of the money that Colombia has received to date has not gone to ground-level efforts to reduce deforestation, but rather to making plans for reducing deforestation and to building the capacity of the appropriate government agencies to measure forest cover and carbon.² However, there has been one notable large-scale effort to shift deforestation dynamics on the ground via a REDD+ project sponsored by the US Agency for International Development (USAID). As additional funding begins to flow in from these bilateral donors to support more of these efforts – such as the commitment of 50 million USD per year that the Norwegian Prime Minister made to President Santos in a press conference in the Colombian Amazon in early April – it is important to make sure that they have learned from these initial efforts led by USAID.

The two years I spent (2016-2017) researching this USAID program, which took place in the tropical rainforests of Colombia’s Pacific Coast, indicate that these deforestation reduction efforts are likely to fall victim to the same suite of vexing issues that plague the peace process in other realms. These include, first and foremost, the ongoing control of much of the country by armed actors – including dissident members of the FARC; other guerillas; and paramilitaries and their offshoots, many of whom are tied to politicians. These thrive on deforesting activities of coca cultivation, gold mining, timber harvesting, monoculture agriculture, and land speculation, and do the dirty work of continuing Colombia’s long history of dispossession of rural farmers from their lands in the process. Second, this deforestation is tied to a lack of access to legal means of subsistence for rural dwellers and those pushed off their land as part of the wider conflict.

While those promoting REDD+ in Colombia seek to resolve this latter issue of livelihood access by paying rural communities to defend the forests around them and offering them “alternative development” projects in the short term, the former set of issues complicate this theory of change. Indeed, hundreds of community activists have been killed by these armed actors since the accords took effect, continuing a long trend of threats and death to those who defend their territories against armed groups in Colombia. As I have seen in my research, the best hope for REDD+’s success is among communities that have legal control of their lands and strong leadership committed to maintaining this control and developing access to legal livelihoods for their community members. The fact that so many of these leaders across Colombia have been killed or forced to flee is obviously a threat to the success of any effort to establish peace, offer more secure livelihoods to rural people, and reduce pressure on the forest. Any positive move to reduce deforestation in Colombia then requires strengthening the implementation of the accord, and going beyond that to address the other actors that are undermining these three supposed concerns of the government.

the best hope for REDD+’s success is among communities that have legal control of their lands and strong leadership committed to maintaining this control and developing access to legal livelihoods for their community members

But while President Santos, who prioritized the peace process above all else, may recognize these mutualistic underlying drivers of discord and deforestation, this is not guaranteed to be the case with his successor. Indeed, the presidential candidate currently leading Colombian polls, Ivan Duque, has suggested he would try to roll back at least part of the peace accord – which could doom the process given the painstaking negotiations and tradeoffs that went into each element of the accord. He has mentioned little about forests other than his ambition to “protect biodiversity” and promote tree plantations – and got his facts wrong about the greatest driver of deforestation in the country in a recent debate on the subject. What his policies might look like in practice are, of course, harder to decipher at this stage. Yet, as Colombians head to the polls on May 27th, my work in Colombia’s Pacific suggests that in the balance lies not only the future of peace in Colombia – both with the FARC and with these other armed actors – but also the future of its rural regions and their forests. If international funders like Norway decide to continue to push their agenda to reduce deforestation in the country in the wake of the elections, they would be wise to emphasize the priorities of the accord, and support the new president in coming to grips with the joint underlying drivers of violence, displacement, inequality, and deforestation across rural Colombia.

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¹ UN Framework Convention on Climate Change
² This is by design within the UNFCCC, which has encouraged a phased approach to REDD+ implementation. The first phase is a readiness phase in which countries are supposed to build up their capacity handle REDD+ funds through these different planning and capacity-building processes.