When visualising land cover and its changes, is there an appropriate temporal scale? What is emphasised and what is obscured by the selection of a land cover baseline?
Monitoring Land Cover Changes
In January 2020, version 5.0 of New Zealand’s Land Cover Database was released. With over 500,000 polygons, it is the most up-to-date assessment of how New Zealanders live on the land (1).
Seen from a distance New Zealand is represented as a solid blue block. Saying nothing other than the coverage of recorded activities. Zooming in to its intended scale of 1:50,000 polygons capturing the different types of land cover become clearer.
But what to make of it? What is clear?
Authors of the database, Manaaki Whenua – Landcare Research, announced the updated data with scientific understatement. Since 2012, the date of the previous version, there has been a “steady decline in wetlands” an “increase in built-up areas” and many changes due to the “routine forestry cycle” (2).
While noting that New Zealand’s land cover is “constantly changing” the over 160,000 hectares of non-routine forestry was still considered “quite a lot” of change in six years within a total land area of 26.8 million hectares.
Why only draw attention to changes since the previous version in 2012? Why this baseline? The Land Cover Database has three earlier versions allowing trends to be traced from 1996, though 2001, 2008, 2012, to 2018 – what do these trends make clear about what New Zealanders think about the land they live on?
“Everything around us is shaped, traversed, and harvested in accordance with cultural imperatives and social needs.”Pawson & Brooking (3)
Looking Further Back
Pushing baselines back further. They are typically shown in three periodisations: pre-Maori, pre-European, and the modern period.
In every period it is a story of deforestation (4) and environmental alteration for human use (5).
Prior to human colonisation in 1280 AD (6), New Zealand was a mesh of dunelands, forests, scrub, tussock, and wetlands (7).
Pushing further back to the extended Last Glacial Maximum c. 29 ka to c. 19 ka, New Zealand is no longer three main islands. Instead it is a single island with an increased land mass covered in shrubs, grasslands, forests, and glaciers (8).
This land is the location of the 100-80 Ma experiment in evolution that New Zealand represents, precipitated by its breaking away from the southern hemisphere super-continent of Gondwanaland.
The Implications of Choosing Baselines
Choosing a baseline from which to discuss land cover change is not neutral. It is the implicit or explicit line from which some deviation is measured. What is better? What is worse? Where should things be heading?
Framing land cover as something that “constantly changes” destabilises the idea of a baseline altogether. Allowing human induced land cover change to range freely until they hit another baseline. For example, like water quality (9).
In 2019, New Zealand assessed that almost 4,000 of its native species were currently threatened with or at risk of extinction. The pressures behind this statistic are land use change, farming, pollution, introduced species, and water extraction (10).
The biodiversity crisis extends globally and is behind such calls as ‘Half Earth’ by E.O. Wilson, which advocate for (re)making room for nonhuman nature by returning half of it (11). In New Zealand prior to 1280 AD, nonhuman nature had 100% of the land for at least 80 million years.
The choice of baseline enlarges or narrows the thought of what is possible and permissible for land cover.
“We have to get rid of this notion that the past is a provider of anecdotes and the present is a provider of knowledge.”Daniel Pauly on shifting baselines
Nearer baselines emphasise the status quo. Narrowing focus to how things are and increasing their sense of inevitability. While more distant baselines create room for alternative landscapes, challenging human timeframes, and serving as reminders of how much land has been taken for human use.
- Pawson, E., & Brooking, T. (2013). Making A New Land. Environmental Histories of New Zealand. Otago: Otago University Press.
- McGlone, M. (2004). Vegetation history of the South Island high country. Report for Land Information New Zealand, Wellington.
- Clark, A. H. (1949). The invasion of New Zealand by people, plants and animals. The invasion of New Zealand by people, plants and animals. Crosby, A. W. (1986). Ecological imperialism: the biological expansion of Europe, 900-1900. Cambridge University Press. Star, P. (2009). ‘Humans and the Environment in New Zealand, c. 1800 to 2000’. The New Oxford History of New Zealand, 47-70.
- Wilmshurst, J. M., Anderson, A. J., Higham, T. F., & Worthy, T. H. (2008). Dating the late prehistoric dispersal of Polynesians to New Zealand using the commensal Pacific rat. Proceedings of the National Academy of Sciences, 105(22), 7676-7680.
- McGlone, M. S., Newnham, R. M., & Moar, N. T. (2010). The vegetation cover of New Zealand during the Last Glacial Maximum: Do pollen records under-represent woody vegetation. Terra Australis, 32, 49-68.
- https://www.half-earthproject.org. See also: Büscher, B., Fletcher, R., Brockington, D., Sandbrook, C., Adams, W. M., Campbell, L., … & Holmes, G. (2017). Half-Earth or Whole Earth? Radical ideas for conservation, and their implications. Oryx, 51(3), 407-410.