Green Referrals on Trial: Separating Evidence from Enthusiasm in UK Nature Prescribing

A decade ago, a suggestion to spend more time in a park would rarely have appeared in a clinical consultation record. Today, in much of the UK, it might arrive through a social prescribing link worker, a community garden scheme or a walking group run out of a GP surgery. Green social prescribing has moved from the fringe of general practice to national policy, and with that prominence comes a duty to be precise about what it can and cannot deliver.

What is actually being proposed

Social prescribing is a model of referral in which primary care staff connect patients to non-clinical community services — exercise classes, advice services, arts groups, befriending schemes and, in the green variant, activities that take place in or around nature. The referral is usually made to a link worker rather than directly to a provider, and the link worker holds a conversation about what matters to the patient before matching them to local assets.

Green social prescribing specifically encompasses organised walking groups, conservation volunteering, community gardening, allotment projects and nature-based programmes for mental health. In England, the concept received explicit national backing through the Green Social Prescribing Programme, launched in 2020 across seven test-and-learn sites with funding from several government departments and arms-length bodies, and evaluated in a report published in 2023. The NHS Long Term Plan had already set out an ambition to expand link worker capacity substantially, and personalised care remains a stated priority.

Where the evidence holds up best

Physical activity. Walking groups are among the better-studied nature-based interventions. Reviews of walking programmes generally find increases in physical activity and modest improvements in cardiovascular fitness and blood pressure, with adherence at least as good outdoors as indoors. The outdoor setting may improve enjoyment and attendance more than it improves physiological outcomes directly. That is a meaningful distinction.

Mental health and wellbeing. Systematic reviews of nature-based interventions report short-term improvements in anxiety, depressive symptoms and subjective wellbeing. Effect sizes tend to be small to moderate, study quality is mixed, and interventions vary so widely that pooling results is difficult. The signal is consistently positive but not strong enough to justify claims of equivalence with psychological therapy.

Social connection. Loneliness and isolation are common reasons for referral, and group-based nature activities plausibly address them through regular, low-pressure contact. Evidence here is encouraging but largely qualitative or based on small samples.

Green space exposure and population health. Large observational studies have linked residential greenness and time spent in nature with lower all-cause mortality and better self-reported health. A widely cited 2019 study in Scientific Reports, drawing on a large English sample, found an association between at least 120 minutes per week in nature and better health and wellbeing. These findings are important and consistent, but they are cross-sectional: healthier people may simply be more able to get outdoors.

Where the claims outrun the data

The most persistent overstatement is the idea that nature prescribing reduces GP workload or saves the health service money. Evaluations have not demonstrated this convincingly, and it is a demanding outcome to measure. Green schemes require link worker time, coordination and transport; they are not free, even when the activity itself is.

A second overstatement concerns the 120-minutes-a-week figure. It is a useful communication device, but it emerged from cross-sectional data, not from a trial establishing a causal dose-response relationship. Presenting it as a prescription target gives it a precision the underlying evidence does not support.

A third concerns generalisability. Most participants in green prescribing schemes are self-selecting and relatively well resourced. Barriers include transport, mobility, confidence, caring responsibilities, cultural expectations about who belongs in the countryside, and the practicalities of weather and daylight in a British winter. Without deliberate attention to these, schemes can widen rather than narrow health inequalities.

Finally, there is the risk of substitution. A green referral is an adjunct, not a replacement for clinical assessment or treatment. For severe mental illness, unexplained weight loss, chest pain on exertion or deteriorating mobility, the correct response remains a clinical pathway.

What a good referral looks like

For clinicians, the quality of the referral depends less on the activity than on the conversation around it.

• Ask what the patient would actually like to do, and whether they would prefer a led group or something self-directed. A referral to a generic suggestion to get outside is unlikely to change behaviour.
• Check practicalities: cost, transport, accessibility, timing, and whether the group is indoors or outdoors in poor weather.
• Consider the season. A scheme beginning in January needs a plan for cold, dark and wet conditions; an autumn start needs a plan for the following spring.
• Think about safety without becoming paralysed by it: falls risk, allergies, cardiac symptoms, safeguarding and insurance for led walks are legitimate considerations that a good provider will already have addressed.
• Agree follow-up. A referral without review is difficult to evaluate and easy to forget.

For patients, useful questions include: is the group led or self-directed; is it free and is transport provided; is it accessible for my mobility; how long does the programme run; and who will check how it is going.

What would strengthen the field

Three things would help. Better outcome measurement, using established measures such as the ONS4 wellbeing questions or WEMWBS, collected consistently rather than selectively. Better comparison groups, including waiting-list or usual-care controls where feasible. And better reporting of who does not take up a referral, since non-attendance is where inequalities are most likely to concentrate.

The balanced conclusion

Green social prescribing is a plausible, low-risk, generally popular addition to the personalised care offer. The strongest evidence supports modest improvements in physical activity, mental wellbeing and social connection among those who engage. The weakest evidence concerns cost-effectiveness, workload reduction and long-term clinical outcomes. For a patient who is motivated, well supported and matched to an appropriate local scheme, a green referral is a reasonable component of a prevention plan. It should be offered as one element of care, described honestly, and followed up — not presented as a cure waiting in the park.