The sixth BUGS paper3 showed that garden area didn’t predict invertebrate species richness for any group of organisms, and in fact for beetles the relationship was negative: big gardens actually recorded fewer species. This may have been because the same numbers of traps were used in the small and large garden, but keen gardeners often cram lots of habitat variety per unit area into small gardens. The same habitat diversity would be spread over a larger area in big gardens, so traps in small gardens would sample greater local variety4.  
 
Even for plants, the relationship between species richness and garden area was not strong (although statistically significant especially for native species). Overall, doubling the garden area resulted in a 24.9% increase in the average number of plant species. However, most of this increase was accounted for by native plants in lawns, and the fact that larger gardens had significantly larger lawns, which in turn showed a positive correlation between lawn area and plant species richness5.
 
The weak link between garden area and species diversity may seem counter-intuitive, and generally in ecology the Species-Area relationship  suggests large areas (or islands) have more species than smaller ones.  There are many other factors at play however, including the “age or maturity” of the habitat, the degree of disturbance and the rate of loss of species and arrival of new ones.  It is also likely that small gardens are functionally linked to all the other adjacent gardens and green space, with a constant interchange of species, making them part of a much larger habitat patch6.
 
 
 
 
Myth: Only big gardens are of value for wildlife
 
There is a grain of truth in this statement, in that if you have a really big garden, there is lots more space in which you could create a wide variety of habitats.  Big mature native trees just aren’t appropriate in a small garden, even less a piece of woodland.  Trees more than 2m high were found to be more common in larger gardens in the fifth paper from the Biodiversity in Urban Gardens (BUGS) project1   – and so were vegetable patches and composting facilities (heaps and bins combined). Research has shown that gardens over 400m2 had more than three times the number of microhabitats than gardens less than 50m2. The same study also showed that gardens with more diverse and extensive microhabitats were associated with higher species richness and moth abundance2.  
 
 
 
Given that so much of the biodiversity of gardens is in the smaller invertebrates, it’s worth noting that for a creature only a few millimetres in length, even a tiny garden must seem enormous.  Jennifer Owen’s garden is 741m2, which is nearly four times the national average of 190m2 but not much above the normal range for detached houses . This unexceptional garden was estimated to hold upwards of 8,450 species of insects alone8.
 
Conclusion
 
Let’s turn this myth around.  It’s great if you're lucky enough to have a big garden, and you can do lots for wildlife in it. But if you have only a small garden, it will still be stuff-full of biodiversity and a source of fascination and pleasure.
 
 
References
 
 
1.   Smith, R.M., Gaston, K.J., Warren, P.H. & Thompson, K. 2005. Urban domestic gardens (V): relationships between landcover composition, housing and landscape. Landscape Ecology 20, 235-253.  Available here
  
2.   Bates AJ, Sadler JP, Grundy D, Lowe N, Davis G, et al. (2014) Garden and Landscape-Scale Correlates of Moths of Differing Conservation Status: Significant Effects of Urbanization and Habitat Diversity. PLoS ONE 9(1): e86925.
Available here
 
3.   Smith, R.M., Warren, P.H., Thompson, K. & Gaston, K.J. 2006. Urban domestic gardens (VI): environmental correlates of invertebrate species richness. Biodiversity and Conservation 15, 2415-2438. Available here
 
4.   Dr Ken Thompson : personal communication
 
5.   Thompson, K., Hodgson, J.G., Smith, R.M., Warren, P.H. & Gaston, K.J. 2004. Urban domestic gardens (III): Composition and diversity of lawn floras. Journal of Vegetation Science 15, 371-376. Available here
 
6.   Goddard MA, Dougill AJ, Benton TG. 2010 . Scaling up from gardens: Biodiversity conservation in urban environments . Trends in Ecology and Evolution 25: 90–98.  Available here
 
7.   Loram, A., Tratalos, J., Warren, P.H. & Gaston, K.J. 2007. Urban domestic gardens (X): the extent & structure of the resource in five cities. Landscape Ecology 22, 601-615  Abstract here
 
8.   Owen, J. 2010 Wildlife of a garden: a thirty-year study. RHS Media
 
 
 
Page drafted by Steve Head: Reviewed by Ken Thompson
In this Google Earth image of a residential area of the district of Kew in London, you can see how the small back-to-back gardens add up to a considerable area – the upper set in this photo measures 5,500 square metres.
 
Myth: Only big gardens are of value for wildlife
 
There is a grain of truth in this statement, in that if you have a really big garden, there is lots more space in which you could create a wide variety of habitats.  Big mature native trees just aren’t appropriate in a small garden, even less a piece of woodland.  Trees more than 2m high were found to be more common in larger gardens in the fifth paper from the Biodiversity in Urban Gardens (BUGS) project1   – and so were vegetable patches and composting facilities (heaps and bins combined). Research has shown that gardens over 400m2 had more than three times the number of microhabitats than gardens less than 50m2. The same study also showed that gardens with more diverse and extensive microhabitats were associated with higher species richness and moth abundance2.  
 
Two smaller gardens from the Sheffield study.  The size of the garden had little effect on wildlife diversity, but how it was used definitely did!
 
 
The sixth BUGS paper3 showed that garden area didn’t predict invertebrate species richness for any group of organisms, and in fact for beetles the relationship was negative: big gardens actually recorded fewer species. This may have been because the same numbers of traps were used in the small and large garden, but keen gardeners often cram lots of habitat variety per unit area into small gardens. The same habitat diversity would be spread over a larger area in big gardens, so traps in small gardens would sample greater local variety4.  
 
Even for plants, the relationship between species richness and garden area was not strong (although statistically significant especially for native species). Overall, doubling the garden area resulted in a 24.9% increase in the average number of plant species. However, most of this increase was accounted for by native plants in lawns, and the fact that larger gardens had significantly larger lawns, which in turn showed a positive correlation between lawn area and plant species richness5.
 
The weak link between garden area and species diversity may seem counter-intuitive, and generally in ecology the Species-Area relationship  suggests large areas (or islands) have more species than smaller ones.  There are many other factors at play however, including the “age or maturity” of the habitat, the degree of disturbance and the rate of loss of species and arrival of new ones.  It is also likely that small gardens are functionally linked to all the other adjacent gardens and green space, with a constant interchange of species, making them part of a much larger habitat patch6.
 
 
 
 
In this Google Earth image of a residential area of the district of Kew in London, you can see how the small back-to-back gardens add up to a considerable area – the upper set measures 5,500 square metres.
 
Given that so much of the biodiversity of gardens is in the smaller invertebrates, it’s worth noting that for a creature only a few millimetres in length, even a tiny garden must seem enormous.  Jennifer Owen’s garden is 741m2, which is nearly four times the national average of 190m2 but not much above the normal range for detached houses . This unexceptional garden was estimated to hold upwards of 8,450 species of insects alone8.
 
Conclusion
 
Let’s turn this myth around.  It’s great if you're lucky enough to have a big garden, and you can do lots for wildlife in it. But if you have only a small garden, it will still be stuff-full of biodiversity and a source of fascination and pleasure.
 
 
References
 
 
1.   Smith, R.M., Gaston, K.J., Warren, P.H. & Thompson, K. 2005. Urban domestic gardens (V): relationships between landcover composition, housing and landscape. Landscape Ecology 20, 235-253.  Available here
  
2.   Bates AJ, Sadler JP, Grundy D, Lowe N, Davis G, et al. (2014) Garden and Landscape-Scale Correlates of Moths of Differing Conservation Status: Significant Effects of Urbanization and Habitat Diversity. PLoS ONE 9(1): e86925.
Available here
 
3.   Smith, R.M., Warren, P.H., Thompson, K. & Gaston, K.J. 2006. Urban domestic gardens (VI): environmental correlates of invertebrate species richness. Biodiversity and Conservation 15, 2415-2438. Available here
 
4.   Dr Ken Thompson : personal communication
 
5.   Thompson, K., Hodgson, J.G., Smith, R.M., Warren, P.H. & Gaston, K.J. 2004. Urban domestic gardens (III): Composition and diversity of lawn floras. Journal of Vegetation Science 15, 371-376. Available here
 
6.   Goddard MA, Dougill AJ, Benton TG. 2010 . Scaling up from gardens: Biodiversity conservation in urban environments . Trends in Ecology and Evolution 25: 90–98.  Available here
 
7.   Loram, A., Tratalos, J., Warren, P.H. & Gaston, K.J. 2007. Urban domestic gardens (X): the extent & structure of the resource in five cities. Landscape Ecology 22, 601-615  Abstract here
 
8.   Owen, J. 2010 Wildlife of a garden: a thirty-year study. RHS Media
 
 
Page drafted by Steve Head: Reviewed by Ken Thompson
  • HomeHome
  • HomeHome