In April 2019, Netflix launched their big-budget nature documentary, Our Planet. Filmed over four years with footage from 50 countries, the sumptuous production rivals any previous series in this genre. While high-profile nature documentaries have been criticized for ignoring the existential threats faced by so many wild species (Monbiot, 2018; Richards, 2013), Our Planet explicitly aims to both explore the 'rich natural wonders, iconic species and wildlife spectacles … and reveal the key issues that urgently threaten their existence' (Our Planet, 2018). We consider how Our Planet differs from previous TV series and discuss why nature documentaries often seem to actively avoid showing anthropogenic impacts. We discuss the mechanisms by which nature documentaries might contribute positively to conservation and identify knowledge gaps in this area.

1. HOW DIFFERENT IS OUR PLANET?

Our Planet talks about the threats to species and ecosystems more than the last three BBC-produced, high-budget nature documentaries (all, like Our Planet, narrated in English by Sir David Attenborough). Nearly 15% of the total word count of the Our Planet scripts focuses on what is not well with the natural world (Figure 1). While this is only slightly more than Blue Planet II, talk of anthropogenic influence is woven into every episode rather than being the subject of a dedicated final episode. Our Planet also regularly shares uplifting tales of species recoveries. Conservation successes (such as the impact of the international moratorium on whaling and the recovery of the Arabian oryx) are mentioned in every episode of Our Planet. While Blue Planet II devoted slightly more of their overall script length to such issues, again this was mostly concentrated in the final episode and not incorporated throughout the series (Figure 1).

The frequency with which recent high-profile BBC nature documentaries and the Netflix Our Planet documentary mention threats to the natural world (red), and positive tales of species recoveries and successful conservation interventions (blue). Coded scripts and further detail are available in the Supporting Information

However, despite the more frequent discussion of threats and conservation effectiveness embedded in Our Planet, visually it is remarkably similar to previous such series. As one commentator noted 'with the sound off, viewers could easily think they are watching Planet Earth' (Young, 2019). While the script regularly talks about the threats facing the habitats and species that are shown, visual depictions of these threats remain rare. There are occasional moments which do effectively show viewers just how altered our world is; satellite imagery is used to show the shockingly rapid loss of rainforest in Borneo for example, and one striking sequence reveals how much of the prairies where rutting bison were filmed have been converted to agriculture. Another hard-hitting scene that received much media attention was that of walruses plunging to their deaths from cliffs, but it was only the voiceover that associated this tragedy with anthropogenic impacts. For the most part, habitats are depicted as extensive and pristine and wildlife populations as abundant.

Interestingly, the makers of Our Planet did produce a hard-hitting and visually stunning eight-minute film, also narrated by Sir David Attenborough, which is available on the accompanying website (How To Save Our Planet, 2019). It was therefore a clear editorial decision to keep the 'feel' of the main episodes similar to previous such documentaries, rather than explicitly showing the extensive anthropogenic impact on our planet.

2. WHY DO NATURE DOCUMENTARIES AVOID SHOWING HOW PEOPLE IMPACT NATURE (AND DOES THIS MATTER?)

Those who make nature documentaries have, of course, long been aware that the nature they film is often drastically threatened. There has been a view that showing the threats would turn audiences off. As the well-known wildlife film maker Stephen Mills wrote back in 1997: '[this] tragic loss of wilderness presents the wildlife film-maker with a fundamental dilemma. So long as we maintain the myth of nature, our programmes find a wide and appreciative audience. …But as viewing figures adamantly prove, once we make a habit of showing the bad news, our audience slinks away' (Mills, 1997). The spectacular images revealing the grandeur of nature in Our Planet may inspire and mobilize concern for the remaining biodiversity found on Earth. While fear and guilt are often used to engage viewers, the importance of hope should not be overlooked (Howell, 2011; Moser & Dilling, 2004). However, one could argue that by using camera angles to avoid showing any sign of people, nature film makers are being disingenuous, and even actively misleading audiences. The viewer may be led to believe that things cannot be that bad for biodiversity as what they are seeing on the screen shows nature, for the most part, doing fine.

There is also the risk that by erasing evidence of people from the land/seascapes shown, wildlife documentaries further embed the idea that wild places are 'for' nature, and any people there are interlopers (Sandbrook & Adams, 2013). This is potentially troubling, as in many parts of the world the biggest challenge conservation faces is balancing the legitimate need of local people to use natural ecosystems with the need to protect those ecosystems from overexploitation. The inextricable link between threats to the natural world and the high consumption of western lifestyles would also be more difficult to ignore if the presence, or even dominance, of commercial agriculture, mining and transport infrastructure were more visible in the landscapes, reducing the space for the awe-inspiring wild spectacles shown.

3. HOW MIGHT NATURE DOCUMENTARIES MAKE A POSITIVE CONTRIBUTION TO CONSERVATION EFFORTS?

While one might expect a public service broadcaster such as the BBC to invest in a documentary for the public good (their mission is to "inform, educate and entertain"; BBC, n.d.), Netflix are driven by a much more commercial imperative. However, there could be a moral obligation for nature documentaries to contribute to conserving the wildlife they show. In 2011, Jepson et al. argued that nature film makers should pay into a fund to contribute to conservation (Jepson, Jennings, Jones, & Hodgetts, 2011); conceptualizing this as a sort of payment for ecosystem services, designed to create incentives for conservation. Wunder and Sheil (2013) pointed out that such a process would likely act more like a tax on nature films and ultimately reduce consumption. Their paper strongly assumes a positive, but unproven, impact of nature documentaries. While requiring nature documentaries to contribute directly to conservation through levying a tax seems unlikely to be helpful, it is certainly legitimate to question whether nature documentaries can indeed make a positive contribution to conservation through less direct means.

Nature documentaries often have a wide reach. Planet Earth II was watched by many millions when it first came out and is now available to stream on Netflix. A producer of Our Planet has stated they hope to reach a billion people (Singh, 2019); the episodes are available simultaneously in 150 countries in 10 languages. How might large viewing figures translate into a positive impact for conservation?

It is well understood by behavioural scientists that the links between information being provided (such as through a documentary) and changes in behaviour are, at best, complex and uncertain (Braun, Cottrell, & Dierkes, 2018; Kollmuss & Agyeman, 2002). However, nature documentaries may elicit change in a number of ways. For example, they have been shown to increase environmental sensitivity toward the species they portray, which is associated with responsible environmental citizenship (Barbas, Paraskevopoulos, & Stamou, 2009). Several studies have gone a step further and attempted to examine the effects of documentaries with targeted conservation messages on viewers' behaviour, by using self-reports of behaviour change/intentions to change (Beattie, Sale, & McGuire, 2011; Hofman & Hughes, 2018; Howell, 2011; Lin, 2013). While they generally report positive effects, the reliability and validity of these measures are questionable and observations of actual behaviour change (though tricky to track) would strengthen the evidence base (Steg & Vlek, 2009).

Documentaries also have the potential to increase support for conservation or conservation organizations through an increase in volunteering, wildlife tourism, or direct donations. They may also generate positive public attitudes and subsequently social norms towards an issue, making policy change more likely. The final episode of the 2017 documentary Blue Planet II has been widely credited with influencing UK policy change on marine plastics (the so-called "Blue Planet effect"; Schnurr et al., 2018). However, the extent to which the documentary, and the resulting public outcry, directly influenced policy change is not well understood.

Our Planet has gone further than previous documentaries to try to encourage viewers into specific actions. At the end of each episode, viewers are encouraged to look at online materials (www.ourplanet.com), which are explicitly focused on threats to the natural world and how individuals can make a difference, for example by eating less meat, switching to renewable energy, or supporting environmental organization. Viewers are encouraged to pledge online to make a change. How effective might Our Planet as a whole (both the episodes and associated materials) be in causing the sort of changes we highlight, and how can we know?

4. HOW COULD THE IMPACT OF NATURE DOCUMENTARIES BE STUDIED?

Although there is growing awareness of the need for robust impact evaluation in conservation (Baylis et al., 2016), one significant challenge for evaluating the impact of nature documentaries is that those who choose to watch such films will tend to have pre-existing interest in the topics presented (Holbert, Kwak, & Shah, 2003). This makes a comparison of the knowledge, attitudes or behaviours of those who watch such documentaries with those who do not an invalid approach for exploring the potential impact of the documentary (Veríssimo, Schmid, Kimario, & Eves, 2018). Experimental approaches can be used to explore the impact of exposure on relatively easily measured outcomes such as 'nature connectedness' or donations to conservation (Arendt & Matthes, 2016; Barbas et al., 2009), or behaviour in a laboratory game immediately following exposure (Zelenski, Dopko, & Capaldi, 2015). More such studies would be useful to explore, for example, the impact of positive or negative framing of conservation issues (a hot topic in conservation science currently; Kidd, Bekessy, & Garrard, 2019; McAfee, Doubleday, Geiger, & Connell, 2019). Another interesting angle would be further exploration of the extent to which outcomes are affected when conservation documentaries focus on an identifiable victim, as opposed to reporting threats statistically (Thomas-Walters & Raihani, 2017). Equally, it would be useful to understand how specifically targeting certain emotions (such as amazement or fear) can influence both cognitive and behavioural change.

However, such experiments are by necessity a simplification of the real world, where viewing a nature documentary is only part of the wider experience. Nature documentaries are often associated with advertising, press coverage and discussion, which can affect the public discourse. Searching 'Our Planet documentary' in Google News for instance returns ~13,000,000 articles. It was also advertised at the US Super-Bowl final and entire London tube trains have been wrapped in Our Planet advertising; this is likely to prompt conversation between peers about biodiversity. In addition, materials and strategies designed to support motivated viewers after watching a documentary, such as the Our Planet website, are an important component of lasting behaviour change and the effects of these need to be accounted for (Hofman & Hughes, 2018). Quasi-experimental approaches (such as Before-After Control-Intervention, e.g. Veríssimo et al., 2018) may be more appropriate to capture the impact of nature documentaries as experienced by the target population. Still, all quantitative methods of evaluation are inevitably limited to simple indicators, such as self-reported knowledge, attitude or behaviour, and over relatively short timeframes.

Qualitative evaluation methods (White, 2009), such as General Elimination Theory or Most Significant Change, will therefore be crucial to understanding the broader impacts of nature documentaries, exploring the causal mechanisms that lead to change, and to capture a wide array or outcomes even outside of the initial stated project aim. Qualitative methods have historically been little used by conservation scientists (Bennett et al., 2016), but there is a growing literature that showcases how these methods can produce evaluation insights that would be out of reach of more quantitative methods (e.g. Moon et al., 2019; Moon, Brewer, Januchowski-Hartley, Adams, & Blackman, 2016; Salazar, Mills, & Veríssimo, 2018; Wilder & Walpole, 2008). Combining qualitative with quantitative measurements, such as in the evaluation of the fictionalized climate disaster film The Day After Tomorrow, can yield insights that are both nuanced and generalizable (Lowe et al., 2006).

Some of the broader impacts of nature documentaries would be very difficult to assess quantitatively, yet they have perhaps the largest potential to catalyse change. Many people working in conservation report that watching documentaries (especially those of David Attenborough) as a child was a key source of inspiration for their career choice (e.g. Fishwick, 2016). In a world where outdoor nature experiences are becoming rarer (Pergams & Zaradic, 2006; Soga & Gaston, 2016), this mechanism may arguably become increasingly important to engage the next generation of people willing to commit their professional lives to tackling biodiversity loss.

5. CONCLUSIONS

By bringing the threats facing nature into the mainstream (however tentatively) documentaries such as Our Planet help biodiversity and the pressure it faces gain a little more space in the minds of the citizens worldwide. This seems inherently valuable in an era where there are ever more demands on our attention. It is hard to avoid the impression that a billion people watching the spectacle of a pod of spinner dolphins, or marvelling at the shuffle dance of the manakins would translate (however indirectly) into an increased chance that these wonders could remain in the wild, as well as on a Netflix playlist. Conservation documentaries have repeatedly been shown to positively affect our attitudes to wildlife, but we still lack a more nuanced understanding of how artistic and narrative decisions influence behaviour change. There is growing awareness of the need for robust impact evaluation in conservation. We therefore recommend that those developing nature documentaries work with researchers for co-creation of impact evaluation, and ultimately for this research to inform subsequent conservation interventions. There is also an excellent growth in interdisciplinary working and methods, as illustrated for example by this new journal People and Nature (Gaston et al., 2019). The time is therefore right to tackle the questions around the extent to which representations of nature on screens affects people in ways which might, ultimately, contribute to conserving that nature.