Eight out of 10 people around the world consider themselves religious. That figure shows that, while in many countries religion is not as dominant as it once was, it still has a huge influence on us.
What does that mean for the environmental movement? Does a belief in God or the supernatural make people more or less likely to take care of animals and the environment?
It is easy to make up stories to answer this question. You might say that many religions push the idea that the world will soon come to an end, in which case surely they encourage a "let it burn" ethos: what does it matter if the rainforest gets cut down, if the Rapture is next week? But just as plausibly, you might point out that many religions are big on kindness, and some such as Jainism even forbid killing animals. This should nudge their followers towards caring for the natural world.
But these are just stories. What does the science of human behaviour tell us?
Let's start with Christianity. Writing in the high-profile journal Science in 1967, historian Lynn White proposed that Christian religions undermine wildlife conservation by advocating a domination ethic over nature. Because the Bible talks about "dominion" over nature, White argued that Christianity teaches its followers that "it is God's will that man exploit nature for his proper ends".
Christian fundamentalists were less willing, and Catholics more willing, to financially support the environment
This was, to say the least, controversial. Other historians and theologians have argued that White was misreading the Bible, and that the text actually implies that we have a duty of care towards nature. Perhaps more to the point, White offered no evidence about the attitudes or behaviours of actual Christians.
In 2013, researchers tackled that question by asking whether there was a relationship between a country's main religion and the number of important biodiversity areas it contained. They found that Christian countries, particularly Catholic ones, tended to have more areas set aside for nature than other countries.
However, this does not mean White was completely wrong. Other studies suggest that conservative Christians really are less environmentally friendly than other denominations.
In a study published in 1993, priest and sociologist Andrew Greeley looked at how much Americans were willing to spend on conserving the environment. He found that Christian fundamentalists were less willing, and Catholics more willing, to financially support the environment. This suggests that it is not whether a person is Christian, but rather what type of Christian they are, that influences their behaviour towards nature.
It also seems that people's attitudes towards the environment can be affected by the way Christianity interacts with other religions.
In her PhD thesis, undertaken whilst at the University of Kent in Canterbury, UK, Emma Shepheard-Walwyn looked at how Kenyans felt about sacred sites. These are places of biological and spiritual significance, created and maintained by communities who adhered to a traditional faith.
A shift away from more traditional faiths could be bad for nature
Shepheard-Walwyn found that "some of the Christian people interviewed felt the forests should be destroyed as they are associated with the traditional faith, which they believe to be evil."
One Christian interviewed said that "tradition is now witchcraft". Others described the sacred sites as places associated with demons and superstition.
This suggests that conflicts between opposing faiths could influence how people feel about protected areas. In particular, a shift away from more traditional faiths could be bad for nature.
In a study published in 2006, Leela Hazzah of Lion Guardians showed that Maasai who had converted from a traditional faith to become evangelical Christians had a higher intent to kill lions than those that kept their traditional faith. "These converted Protestants did not have very positive attitudes towards national parks or wildlife either," says Hazzah.
Christianity can play a part in how, and indeed whether, we think about nature
Because the Maasai are not exposed to much television or other media, they look to their pastors for information about the world. If a pastor does not include positive stories about nature in their sermons, the churchgoers would not get any guidance on how to be environmentally friendly.
The evangelical churches also ran religious events, sometimes a week long, which pastoralists were invited to attend. That meant no one was around back at the homestead to protect the livestock from predators. Two pastoralists lost 35 cows during one such event. When Hazzah asked them why they left their livestock unattended for so long, one man replied: "There is no need to return home when I am in the house of God. He will protect my livestock from danger".
All this suggests that Christianity can play a part in how, and indeed whether, we think about nature. So how do other religions compare?
A study published in August 2016 analysed Indian people's attitudes towards large carnivores. It found that Buddhists tended to have more positive attitudes towards carnivorous animals than Muslims.
Given Buddhism's reputation for avoiding all harm to animals, this may not come as a surprise. However, the findings are not quite as straightforward as they first appear.
Religious practitioners and leaders... have a potentially important role in conserving nature
The more often a Buddhist undertook religious activities, the more likely it was that they had a more positive attitude towards wolves and snow leopards. In other words, the link between Buddhism and pro-environment attitudes was only apparent for the more deeply religious Buddhists.
As with the study of American Christians, the key issue is not whether or not a person is religious, but rather the form their religion takes: in this case, how devoted they are to it.
These findings mean that conservationists must frame their messages differently depending on the audience, says lead author Saloni Bhatia of the Nature Conservation Foundation in Mysore, India. "We must stress environmental stewardship with Muslim communities and religious leaders, while the idea of human-wildlife interdependence would resonate more strongly with the Buddhist communities and leaders."
In other words, conservationists need to integrate their ideas into religious thinking. "Religions, and certainly the versions of Islam and Buddhism that we have studied, seem to have well-developed philosophies towards nature and wildlife," says Bhatia. "Religious practitioners and leaders therefore have a potentially important role in conserving nature."
But instead, conservationists and religious leaders have largely grown apart.
Shepheard-Walwyn believes conservationists have mostly ignored religion because of "the false belief that science and religion don't mix, and that to be a good scientist you cannot engage with religion, because they feel religious people apply less rigorous science to their work."
She also thinks there are problems with the ways conservationists and religious individuals talk about nature. The two parties are not, so to speak, singing from the same hymn sheet.
The sheikhs spread the information to their community and, as devout Muslims, the fishermen listened
However, some groups are trying to bridge this divide.
The Alliance for Religions and Conservation (ARC) is a secular body that helps faith leaders to create environmental programs based on their faith's core beliefs and practices.
One of their most successful projects is based on an island off the coast of Tanzania. Fishermen there had been using dynamite as a quick and easy way to bring in the day's catch. But this method of fishing is very damaging, destroying coral and killing immature fish and turtles.
Local conservation organisations tried to educate the fishermen on the harms of dynamite fishing, but this fell on deaf ears. The government then banned the practice, but again the fishermen took no notice. Then ARC stepped in.
ARC members realised that all the fishermen were Muslim, and that the local sheikhs had a lot of influence in the community. So they showed the sheikhs passages in the Koran that promote pro-environmental behaviour, and told them that dynamite fishing goes against these teachings. The sheikhs spread the information to their community and, as devout Muslims, the fishermen listened.
In Tanzania they have created an Islamic eco-village for orphans
One local fisherman, interviewed in the Christian Science Monitor in 2007, said: "I've learned that the way I fished was destructive to the environment. This side of conservation isn't from the mzungu ["white man" in Swahili], it's from the Koran."
ARC was not the only organisation involved with the fishermen. Another key party was the Islamic Foundation for Ecology and Environmental Sciences (IFEES).
Its founder Fazlun Khalid started the organisation in the 1980s because of his passion for nature. After studying theology at university, Khalid concluded that Islam is intrinsically environmentalist.
But he also noticed that Muslims had lost their connection with nature, because like so many other people they had become preoccupied with wealth. So he set up IFEES to show Muslims the core teachings of the Koran that convey an environmentalist ethic.
In Indonesia, a country rich in biodiversity but under threat from development, IFEES is working with schools to restore the rainforests.
Similarly, in Tanzania they have created an Islamic eco-village for orphans, where they are establishing renewable energy plants and recycling projects. "This eco-village was built based on the practices of the prophet on how to manage natural resources," says Khalid.
Conservationists can learn a lot from religion about how to engage people and build support
Khalid believes that there is a new global religious movement building, which is keen to embrace nature. "Faith-based organisations played a key role in the recent climate change negotiations, and IFEES were cornerstones in the creation of the Islamic Declaration on Climate Change," he says.
There is some tentative evidence that this sort of approach can work.
A 2013 study in Indonesia showed that incorporating conservation messages into Islamic sermons increased both public awareness and levels of concern. "Since then, Indonesia [has] issued its first fatwas [rulings on Islamic law] prohibiting illegal wildlife trafficking and poaching," says lead author Jeanne McKay of the University of Kent.
Beyond that, ARC argues that conservationists can learn a lot from religion about how to engage people and build support. After all, religions are famously good at garnering lots of followers all devoted to a common cause.
ARC says that, first and foremost, religions are great at telling compelling stories that can inspire and inform. They also tend to celebrate what we already have, rather than focusing on what we have lost. Conservationists may want to heed their example.
Incorporating conservation messages into Islamic sermons increased both public awareness and levels of concern
When we read stories about the environment, we can be confronted with narratives of doom and gloom about how yet another species is closer to extinction or how we have destroyed even more wilderness. This is all factually correct, but research suggests that stories with a positive framing are better at motivating people to act than stories with a negative framing. In other words, feel-good stories can be very powerful.
"Using faith-based approaches can prove to be a positive way forward, and indeed has the potential to gain far-reaching benefits rather than staying confined to a conventionally science-based approach," says McKay.
It would be silly to downplay the environmental crisis we are facing. But in order to solve it, conservationists may need to harness the power of hope and optimism, just as the world's religions do.
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