We have created for CCAFS a database of crop distributions covering 85,000km2 from Kwale on the Kenya coast, across Kenya to Uganda and the DRC. All data in this database were collected by Aerial Point Sampling which uses high resolution, full colour, sample aerial photography. Some 30,000 sample points make up this database. For mapping purposes, the cover density of crops are summarised into 5km * 5km UTM grid cells.
This shows the distribution of maize across the database. The objective here is to compare the distribution of maize modelled from agro-climatic models against the actual, observed distribution.
Similarly with bananas. The data base holds distribution data on 19 crops.
In mid 2012 CCAFS/GRP6 provided funds to resample the western and central parts of the area covered by the database, a total of 60,000 km 2 , to give a 30 year perspective of landcover and landuse change.
APS uses very high resolution, full colour sample photography from which land cover and land use attributes are measured; some 6,000 samples covered this area; each sample approximately 3ha (200m * 130m). From each photograph were obtained:- Metadata: 17 variables on geographic location, time and date stamps, photo-dimensions and interpretation history. Primary Data: 7 data variables describing the natural vegetation, 31 describing crops and agricultural activities, 11 for infrastructure, and 5 miscellaneous. Secondary data: primary data were recombined into new variables, e.g. total agriculture, active cultivation, agro-forestry .... Since each sample is geo-referenced it is possible to associate any other spatial data: Administrative -- country, location; physical - altitude, slope angle; environmental -climate zone, rainfall, temperature, available moisture; infrastructure - distance to roads, markets...; bio-physical - soil type and characteristics; socio-economic -- population density, land tenure
The most noticeable change over the last 30 years has been in the area under cultivation which has increased from an average of 42% cover …..
… .. to 63% cover, an increase of 1.3 million hectares at an annual rate of 1.4% per annum
Cultivation has expanded both in extent and in intensity. Compared with 1983 …….
… . the land was being much more intensively used in 2013
In 1983 only 40% was used at >50% intensity, today it is 70%.
There is much talk about "sustainable intensification" and we have looked into this. We can find no indication that, as a general pattern, land used intensively 30 years ago is used less intensively today. Intensity everywhere has increased. However, it does seem that above 80% there is some sort of threshold above which no significant change, either increase or decrease, can be determined.
Nonetheless, some areas have “ gone backwards ” and show a significant reduction in intensity of use. The great majority (60%) show a statistically significant increase, some 35% are probably best described as no change, and 5% show a significant decrease., Associated with the areas of decrease (red) are very high population densities and expansion of infrastructure (towns). Some also fall in areas that suffered from PEV.
Land tenure has a major effect on development trajectories. We consider here adjudicated land – either leasehold or freehold – and unadjudicated land (no formal title deed). Although cultivation has increased substantially on both adjudicated land …..
… . and unadjudicated land, the unadjudicated land remains some 40 years behind the development trajectory of adjudicated land. Of the 1.3 million ha brought into production, only 12% was on the 30% of untenured land.
The expansion of cultivation as been at the expense of the natural vegetation which has shown a stark decrease. Basically, natural vegetation has decreased by -42%, from 54% to 31%, a loss of 1.3 million hectares at an annual rate of -1.8% per annum
But what is interesting is that the loss of natural vegetation has been primarily at the expense of herbaceous cover rather than woody cover. What we are seeing here is the gradual evolution of the landscape from a more natural to a more managed state, with areas of natural vegetation – especially herbaceous vegetation -- being converted to cultivation.
Let us look more closely at changes to Tree cover. Overall, there is a modest loss of -3% in total tree cover across the landscape over the last 30 years at a rate -0.6% per annum, surprisingly low.
But there has a major change in the structure of the tree cover, from natural tree cover to managed tree cover. This managed tree cover is what we call agro-forestry , and there has been an expansion of 215,000 hectares over the last 30 years, at an annual rate of 1.1% per annum. So we see a second evolutionary process here from natural trees to managed trees. In the same way as we transform wild animals into domestic livestock we are transforming wild vegetation into domestic vegetation.
This shows the gains in hectares of different agro-forestry components over the last 30 years. Only plantations show no significant increase. Note that some 207,000 km of hedgerows have been planted.
On unadjudicated land there is a clear loss of tree cover compared with adjudicated land where total tree cover remains unchanged. In other words, the observed loss of tree cover across the landscape is related solely to the untenured land.
On adjudicated land, the increase in agro-forestry has more than compensated for the reduction in natural tree cover.
In contrast, on unadjudicated land the investment in agro-forestry has not compensated for the loss of natural tree cover. Natural tree cover is being mined on unadjudicated land.
It is intriguing that landowners and users under different tenure regimes invest in different aspects of agro-forestry. On unadjudicated land, the major investments are in the “ landscape ” components of agro-forestry -- hedgerows, windrows and scattered trees. This suggests that these investments are being made primarily to increase the security of tenure.
Are Forests doing a good job? Certainly, natural tree cover is higher, and has shown a smaller loss, in protected forest areas compared with the unprotected landscape.
On Mount Elgon, there is still a marked “ forest boundary ” between the protected forest and the areas outside.
However, the situation is not so clear in and around the Mau Forest complex. No clear boundary between “ inside ” and “ outside ” can be seen ……..
… .. and agriculture has moved deep within the forest complex.
The human population has increased from some 8.4 million in 1979 to ……
…… .. to 17.3 million in 2009, an increase of some 9 million people (106%).
There is a strong positive relationship between the rate of population growth and the growth in agriculture. However, the number of people supported by each hectare of cultivated land has only increased by 35%, from 4.6 people per hectare to 6.2 person per hectare.
The strong relationships between landuse *(e.g. agricultural intensity, distribution of individual crops) and climatic factors (e.g. agro-ecological zones, rainfall, temperature) suggest that landuse would be very susceptible to climate change.
However, the marked variation within climatic (or rainfall, or temperature) zones suggests otherwise.
The strong patterns of change in rainfall over the last 30 years …….
… . are not reflected in land use patterns, …….
… . neither are the changes in temperature …
Of course, adaptation to climate change may not be shown in landscape scale changes in crop distributuion but in more subtle measures of crop management, planting and harvesting times etc.
Presentation on drivers of landcover and landuse change in Kenya
DRIVERS OF LANDCOVER AND LANDUSE
CHANGE IN KENYA 1983 – 2013
Mike Norton – Griffiths, Dphil., Snr. Research Fellow, ICRAF.
Harvey Herr, GIS Consultant, ICRAF.
Managed trees (aka trees-on-farms aka agro-
forestry) replace natural trees
Increase in Agroforestry 1983 2013
of 215,000 hectares
Woody Crops Ha 29,000
Woodlots Ha 48,000
Plantations Ha 16,000
Scattered Trees Ha 60,000