Natural forest restoration: purpose, challenges and values. M. Nicholson Brackenhurst Botanic Garden

Transcription

1 Natural forest restoration: purpose, challenges and values M. Nicholson Brackenhurst Botanic Garden

2 Brackenhurst Botanic Garden An Ecological Restoration Project ha. Private and protected 1500 indigenous plant species on accessions list (450 shrubs and tree species)

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5 Purpose of native forest restoration 1. To address the global loss of biodiversity (anthropocene extinction) which is times the rates of background extinction. Restoration, however small scale, can help preserve species threatened with extirpation (e.g. Pistacia aethiopica in Nairobi) and/or extinction 2. To restore ecosystem services: water quality, water provision, air quality, soil quality, soil conservation, ecotourism 3. To be a buffer against land conversion by roads, urbanization (residential & industrial), monoculture, which is usually a one way process and often irreversible

6 Mark Twain and statistics Kenya's forest cover has tripled over the last 10 years increasing allaying fears of massive environmental degradation. According to Kenyan government statistics released in March 2012, forest cover had risen from a low of 1.7 per cent in 2002 to 5.9 per cent. Kenya Forest Service director Mr. David Mbugua said the natural resource that was facing extinction in There has been a straight line decrease in forest cover in Kenya between 1990 and 2012 Year Value (km 2 ) , , ,450 Source: KFS Source: FAO

7 Threats Maasai Mau: forest destruction: short-term gain; long term loss Drive path Photographs Photograph taken on 21 April 2005

8 Kijabe KFS office June 2015 >7000 loads /yr

9 July 2015

10 Land conversion

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12 2015

13 Challenges of restoration 1. Time our project has a 30 year time span 2. Costs: forest restoration in the first 5 years cost between $3000-$6000 ha per year till canopy closure (SER 2013). Clearance, hole digging, nursery, seed/ wilding collection but depends on starting point (forest enrichment/ plantation clearance), country, labour costs etc.thereafter it depends on costs of site protection and removal of invasive species 3. Invasive species the biggest single threat to success 4. Limited knowledge: more education required on taxonomy, propagation, ecology and uses of indigenous flora 5. Gazettement of private forests? Forest Act 2005?

14 Education: Burro Women honey group, Garissa

15 Value of restoration 1. Biodiversity conservation and seed source 2. Ecosystem services: Water 3. Soil 4. Air 5. Food and medicine 6. Timber 7. Ecotourism 8. Mental health benefits (colour, birdsong etc)

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18 Water

19 Air quality Young forests absorb CO 2 at a greater speed than mature forests (about 6t C ha -1 /yr). Forests also absorb other pollutants (O 3, CO, SO 2 & NO x ) making them invaluable in urban environments (Karura, Ngong). One tree was measured removing 60mg Cd, 140 mg Cr, 82 mg Ni & 5200 mg Pb Trees also remove diesel and charcoal particulates. Shade reduces soil/air temp and oxidation of SOM

20 Soil conservation & soil quality Forests reduce the erosivity of rainfall and the erodability of soils owing to leaf litter and SOM Soil organic matter (SOM) was the only parameter other than water which was always positively correlated with crop yield (KARI, 1992) SOM is far higher under natural forests than plantation forests or cropland. SOM is rapidly oxidized by sunlight and burning and rapidly accumulated under forest Deforestation leads to soil erosion, storm flow and seasonal stream flow

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23 SOM at 20 cm cf. degraded wattle 3.5%

24 Indigenous Timber production (clear felling) Meru oak: 20 yr cycle Planted 1995 Dbh 45 cm/ 6m Yield 0.6 m 3 Value $ m 3 Density: 156 /ha Potential revenue: $101,400 Other species: Olea welwitschii, (O. europea), Ocotea usambarensis, ocotea keniensis, Cordia africana

25 Non-timber forest products Honey Indigenous vegetables Coffee Medicine Fish poison

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27 Medicines Phytolacca dodecandra- molluscicide vs schistosomiasis Prunus africana - BPH Warburgia africana antibiotic + >400 spp. used for medicine in Kenya Amazon believed to have species of medicinal interest

28 What do we know about the uses of associated spp. in forests medicines, pollination etc?

29 Ex situ conservation

30 Conservation requires both observation AND taxonomic expertise

31 Cylicomorpha parviflora Ex situ conservation Ex situ conservation: W. Whytei & W. cedarbergensis

32 People pay to see trees: IDS Feb/ March 2015

33 Strychnos innocua One Kenya collection (KTSL) Properties?? Cf. Strychnos henningsii

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35 Ecotourism

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37 Is this the Kenya we want?

38 Or this?