Monthly Archives: May 2012

Erosion control, Grevillea and the hills around Aksum, northern Ethiopia – videoblog

Hillside erosion following deforestation for firewood and overgrazing -  Aksum, Ethiopia

Hillside erosion following deforestation for firewood and overgrazing - Aksum, Ethiopia

Erosion is one of the most environmentally destructive processes, leading to loss of biodiversity in plants and animals, as topsoil with all its nutrients washes and blows away, ending with stony ground that cannot sustain plants or store water. When water is not stored, plants need continuous rain, making them drought-prone, and rainfall runs off fast, causing flooding downstream, collapse of hillsides, and silting up of dams (although seasonal inundations with topsoil and its nutrients have been part of traditional cropping in many areas).

I sometimes ask classes to think about the question of ‘how far is the human race from extinction?'; answers come back in terms of the months of food we have stored now, the random time until the next huge volcano erupts or asteroid hits us, the years until there is not enough food with current unsustainable production methods, or a few decades before wars over water or hunger lead to our extinction. My answer to the question: we are about 15 cm or 6 inches from extinction, the depth of the topsoil that sustains most plant and microbial life.

Erosion has been with us from the start of agriculture: traditional slash-and-burn agriculture was able to grow crops for only a few years before plots lost topsoil and nutrients, so they were abandoned without production for several decades before restarting the cycle. Landscape-wide erosion caused huge areas of limestone to be exposed in the Burren area of Ireland, now interestingly conserved as a very special ecosystem but with minimal biological productivity compared to the temperate rain forests that preceded the limestone pavements. In the US, the dustbowls of the 1930s, with many plowed (ploughed) and fallow fields displacing deep-rooting perennial grasses.
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In the video, we start with the hillsides behind the city of Aksum (Axum) in Tigrai, northern Ethiopia, about 45km / 30 miles south of the Eritrean border. Eucalyptus is growing at the top of the hillside, but between the settlement and the top, it is obvious that in recent years, all the sticks and wood have been collected to burn in open fires, while smaller plants have been eaten by groups of goats driven by a goat-herd. While the top of the hill, still with Eucalyptus, only has a few visible rocks and stones, much of the sandy soil the lower part of the hillside has washed and blown away leaving boulders exposed. Among the few plants doing well, as seen in the walk up to the base of the hillside, is the central American invasive poppy species, Argemone mexicana. This is one of the few plants that is ‘goat proof’ with both vicious spines and toxic seeds (resembling closely Brassica seeds): it has no value.

I didn’t see any signage about the erosion control project, but it was clear that goats and firewood collection had been controlled within the area being planted. Rudimentary terracing had been constructed, important to slow the runoff of surface water, as farmers have known for 8000 years. In pits, some Eucalyptus has been planted, but mostly another Australian species is being introduced, Grevillea robusta. This is physically the largest species in the plant family Proteaceae, growing upto 35m tall, and does well in dry forests with more than 1000mm rain per year, and it seems to be increasingly used for erosion control by planting along contours or in gulleys. As well as the men involved in planting, irrigation is critical and a chain of women is seen carrying 25 litre yellow containers of water about 1km from the water tanks, involving a steep climb of 100m or more up the slopes starting at 2100 m in the highlands. In flatter areas, donkeys are carrying four of the containers. Presumably, the employment from this

Grevillea robusta plantings for erosion control on terraces above Axum

Grevillea robusta plantings for erosion control on terraces above Axum

back-breaking work is more valuable than an expensive pumping and piping system. The containers themselves are reused 25 l drums from palm oil, notably imported from Indonesia, rather than across from the traditional producing areas of West Africa.

Women carrying 25litre drums of irrigation water up an eroded hillside

Women carrying 25 litre drums of irrigation water up an eroded hillside

From 400BC, Axum was a powerful centre and the capital of the Aksumite kingdom until the 10th century. Among the reasons quoted for the fall of the empire was environmental degradation and over-farming, along with climate change. Hopefully the erosion control and reforestation seen in this video will enable the current Axum to increase its prosperity in the next few years.

Part of
This material is used in University of Leicester course BS2072 – Biodiversity and Sustainability.

Related video: Grain and Chilli Mills in Axum

Ethiopian cereal and chilli mills: making flour in the market from corn, tef, wheat and chilli

See on Scoop.itAnnBot

Flour milling in the west happens out of view! Here we can see three different grains being milled in two larger stone-mills, each with two pairs of electrically driven stones, and some grinding machines (probably cone pulverizers) are used for smaller quantities of less fine flour and also chillies. We see the traditional Ethiopian grain tef (Teff, Eragrostis tef, with tiny grains 1mm x 0.7 mm), wheat and white maize coming to the mills in 50kg sacks, and then the women sieve and winnow it in the air. It is then put into the grinder. For chilies in the final third of the video, women were buying them in the 5kg quantities in the market and thanking them to be ground at the mill – a quick search suggests that an Indian machine from was being used! The chillies were mostly very hot and the dust caught your throat. There didn’t seem to be much protection from explosion in the flour mills.


Unlike the video of the Indian flour mills I posted earlier, , there was no sieving process to separate flour and bran. These mills are in Axum (Aksum), Ethiopia.

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Seed banks on stems of wetland palms

Seed banks on stems of wetland palms

Seed banks on stems of wetland palms

Seeds can accumulate in the soil or elsewhere, and one potential site is on the stems of palms when these are covered by persistent sheaths. Corrêa et al. study sheaths of Attalea phalerata (Arecaceae) in the Pantanal wetland of Brazil and find that 65 % contain seeds, belonging to 75 species in 12 families. This seed bank is primarily made up of small, endozoochoric seeds, with both abundance and species richness being greater in the wet season than in the dry. Seeds of some species such as Cecropia pachystachya (fig) are able to successfully establish seedlings on palms and become adults. The palm stems can thus provide safe sites where seeds (and seedlings) can escape flooding.

Annual increments of juniper as a climatic proxy

Annual increments of juniper as a climatic proxy

Annual increments of juniper as a climatic proxy

Dendroclimatology can play an important role in understanding past climatic changes, and where trees are not present it may be possible to utilize shrubs instead. Liang et al. examine the dendrochronological potential of Wilson juniper (Juniperus pingii var. wilsonii) growing at high altitudes from 4740 to 4780 m a.s.l. on the Tibetan Plateau, and find reliable cross-dating between ring-width variability and distinct climatic signals. One individual is 324 years old, thus making the species a potentially valuable source of data. The results also suggest that moisture during summer months is a limiting factor in the growth of the plant.

Soil heterogeneity and intraspecific competition

Soil heterogeneity and intraspecific competition

Soil heterogeneity and intraspecific competition

Spatial heterogeneity in nutrients may increase the relative competitive ability of species that are more able to concentrate their roots where nutrient levels are high; if so, heterogeneity should have little effect on intraspecific competition when no genotypic differences exist between individuals. Zhou et al. grow a clonal invasive herb, Alternanthera philoxeroides (Amaranthaceae), at different plant densities with homogeneous or hetergeneous availability of soil nutrients and find no interactive effects on growth, consistent with the suggestion that effects of heterogeneity on competition depend upon differences in plasticity between individuals.

Proof of phytological principle

Image: Becker & Marin (2009)

Image: Becker & Marin (2009)

Sadly, we don’t have time machines that would permit us to go back and see ancient evolution in action. So we have to make do with such devices and stratagems as inference, surmise, speculation, good honest-to-goodness old-fashioned guesswork, and investigating modern-day equivalents that might mimic the original phenomenon. Take for instance colonisation of the land by ‘plants’. Arguably, this was one of the most important events in creation of the modern-day planet we call home, but how could ‘terraphyte’s’ ancestors survive a much drier land-living existence and thus pave the way for a terrestrial take-over? Trying to get a handle on early plant adaptation to land, Linda Graham et al. have studied how well assumedly obligately aquatic algae could survive an ‘aeroterrestrial’ existence (i.e. living on and in soil, or covering surfaces such as rocks and tree barks; The group used ‘two species of the experimentally tractable, complex streptophyte algal genus Coleochaete’, chosen because it is one of the extant green algal genera most closely related to the embryophytes – the so-called ‘land plants’ ( see Burkhard Becker and Birger Marin’s Botanical Briefing in Annals of Botany)  – and therefore a plausible putative palaeological plant progenitor. What they discovered suggests that ancient complex streptophyte algae could grow and reproduce in moist subaerial habitats, and persist through periods of desiccation – as you’d need to in order to occupy a drier habitat. Consequently, land colonisation could be envisaged by ancient Coleochaete-like organisms (which are freshwater aquatics). Which is good to know, and also accords with the very latest ideas in terms of identifying the nebulous ‘crucible of creation’, which may not have been the oceans – as long thought – but freshwater ponds, according to work by Armen Mulkidjanian et al. (PNAS). Whilst this may upset the apple-cart of received wisdom in that field in challenging firmly held, long-cherished beliefs, at least it’s still arguing for an important aquatic dimension (even though it can be argued that it actually proposes that life on Earth originated on land – but let’s leave further deliberation thereon to the semanticists…). But! – and as pointed out by others – this 21st Century idea is reminiscent of the notion that evolution may have begun in a ‘warm little pond’, posited by a certain Mr C. Darwin in 1871. Which only goes to show that there’s practically nothing in biology that has not already been created by CD (and that ideas about evolution just keep evolving!).

[Mr Cuttings thought he’d invented the word terraphyte in penning this item. Well, he had, but not originally it would seem. In a ‘covering his backside’ moment, an internet search has revealed that the term has been used previously by ‘aquetus’ – interestingly in an article that has a strong warning about plagiarism – Ed.]

FAO Statistical Yearbook 2012: all you ever wanted to know about world crop yields and tonnages

See on Scoop.itAnnBot

“The 2012 edition of the FAO Statistical Yearbook presents a visual synthesis of the major trends and factors shaping the global food and agricultural landscape and their interplay with broader environmental, social and economic dimensions.


In doing so, it strives to serve as a unique reference point on the state of world food and agriculture for policy-makers, donor agencies, researchers and analysts as well as the general public.


The book is subdivided into four thematic parts:


The setting measures the state of the agricultural resource base, by assessing the supply of land, labour, capital, inputs and the state of infrastructure, and also examines the pressure on the world food system stemming from demographic and macroeconomic change


Hunger dimensions gauges the state of food insecurity and malnutrition, measuring the multitude of dimensions that give rise to and shape undernourishment


Feeding the world evaluates the past and present capacity of world agricultural production and the role of trade in meeting changing food, feed and other demands


Sustainability dimensions examines the sustainability of agriculture in the context of the pressure it exerts on the environment including the interaction of agriculture with climate change, and how it can provide ecosystem services in relation to the bio-based economy”

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Origins of woodiness in Balsaminaceae

Origins of woodiness in Balsaminaceae

Origins of woodiness in Balsaminaceae

The family Balsaminaceae, which contains the species-rich genus Impatiens and the single-species genus Hydrocera (H. triflora), is essentially herbaceous and is nested into a largely woody clade of Ericales. Lens et al. compare a molecular phylogeny of Balsaminaceae with wood anatomical observations to determine whether the woodier species are derived from herbaceous relatives (i.e. secondary woodiness), or whether (primary) woodiness represents the ancestral state. The data show that secondary woodiness has evolved at least five times in parallel within Impatiens; however, these parallel shifts are indistinct because of the continuous variation in wood development between herbaceous and woody species.

Satellite DNA family in Medicago and allied genera

Satellite DNA family in Medicago and allied genera

Satellite DNA family in Medicago and allied genera

Satellite DNA is a genomic component present in virtually all eukaryotic organisms and is an important element in genome organization and evolution in plants. Rosato el al. assess the presence and physical distribution of the repetitive DNA E180 family in 70 accessions from Medicago and allied genera. The results suggest that recurrent and independent evolutionary episodes of amplification appear to have been produced in both annual and perennial Medicago species as well as in basal and derived clades, and hence the use of repetitive DNA families as phylogenetic markers in this genus should be viewed with caution.

On our Scoop It between April 26th and May 13th

These are links from our Scoop It page between April 26th and May 13th:

Fishing Lake Hawassa, Ethiopia: Rift Valley lakes and catching Tilapia and Catfish

Fishing boats on the side of Lake Hawassa, Awassa in the Rift Valley of Ethiopia. Opening with a view of lake from a park next to the shoreline where fish is landed, the film shows the landing, folding of nets, gutting and preparing of hte fish.

Drug-making plant blooms

Approval of a ‘biologic’ manufactured in plant cells may pave the way for similar products.

First Drug from GM Plant Approved

This week (May 1), the US Food and Drug Administration approved the first drug for humans produced by a genetically modified plant. Made by Israeli biotech Protalix Biotherapeutics and licensed in the US by Pfizer, Elelyso is an enzyme replacement therapy for Gaucher disease, a rare genetic disorder in which individuals do not produce enough of an enzyme called glucocerebrosidase, resulting in the buildup of fatty materials in the spleen, liver, and other organs.

Ecosystem effects of biodiversity loss could rival impacts of climate change, pollution

Loss of biodiversity appears to impact ecosystems as much as climate change, pollution and other major forms of environmental stress, according to a new study. The study is the first comprehensive effort to directly compare the impacts of biological diversity loss to the anticipated effects of a host of other human-caused environmental changes.

Theobrominated: Is biology zoonormative?

A geneticist colleague once told me a story about hiking with another biologist. The forest was quiet and still, from the emergent podocarps and the tawa canopy right down to the ferns and mosses on the forest floor (sadly often the case in New Zealand forest since introduced mammals ate most of our native birds). The other biologist's reaction to this was to say, "It's so quiet; there's nothing alive here!" To what extent is our thinking and teaching in biology zoonormative?

Why taxonomy is important for biodiversity-based science

Taxonomy usually refers to the theory and practice of describing, naming and classifying living things. Such work is essential for the fundamental understanding of biodiversity and its conservation. Yet the science behind delimiting the natural world into “species” is often neglected, misunderstood or even derided in some quarters.

The paper give the example of rattans of Africa, leading to the publication of a taxonomic monograph of these climbing palms. Taxonomic work of this kind is not purely an academic exercise. It is an essential basis for the conservation, development and management of the resource itself. It is important that the differences between species are clearly understood so that we know which species are of commercial importance and how they can be distinguished from other species that are not utilised and why. This knowledge is essential in order to undertake meaningful inventories of commercially important species and to be able to assess the potential of each species for cultivation and sustainable management. A structured taxonomic framework also ensures that any experimental or development work undertaken is replicable.

Sperm racing: the tortoise and the hare

Once they conquered the land, the earliest land plants (the bryophytes) were like the amphibians: they can live on dry land, but they need water for mating. The seed plants acquired a kind of internal fertilization, because they use pollen grains to deliver their sperms right to the stigma or the ovule, where a pollen tube can take it the last few millimetres to the egg. In this, the seed plants resemble the mammals. However, this is an analogy. These plants are doing similar things to the animals for similar reasons, but in completely different ways.

Science of the Invisible: Google+? It’s very simple

f you’re interested in science communication, or learning about science, Google+ is the hot place to be. In January 2012, Google changed the game when it introduced “Search plus your world”, adding a social element to search results. Talk to any publisher and they will tell you that Google is still by far the biggest player in search, so if you want people to read about your science, you need to pay attention

IWMI : CGIAR Research Program on Water, Land and Ecosystems – Overview

Worldwide research initiative launched to tackle global crises in water, food and the environment


An ambitious new research program, launched by the world’s largest consortium of international agricultural researchers, aims to address some of the world’s most pressing problems related to boosting food production and improving livelihoods, whilst simultaneously protecting the environment.The program focuses on the three critical issues of water scarcity, land degradation and ecosystem services, as well as the CGIAR System Level Outcome of sustainable natural resource management. It will also make substantial contributions to the System Level Outcomes on food security, poverty alleviation and, to a minor extent, health and nutrition.

RuSource: Economic evidence for investing in the environment

There are many examples where green infrastructure offers much better value for public investment than the alternative, for example natural water filtration and natural flood defence.

Alan Spedding over at RuSource had identified and summarized an important report with the less-than-exciting title "Natural England Research Report NERR033 ‘Microeconomic Evidence for the Benefits of Investment in the Environment – review’.


Natural climate control is much cheaper than the air-conditioning (or heating) it replaces. Natural air filtering is likely to be efficient compared to technical alternatives, particularly as trees provide so many other benefits. Access to greenspace and the promotion of active travel are extremely cost-effective ways to address Mental and physical ill-health.


From RuSource and Natural England