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The late 19th and early 20th century was a time of intensive geological surveys, carried out in an atmosphere of national romanticism. This period has been described in a recent book by science historian Christer Nordlund, which is here presented and commentd on. Of special interest in Sweden was the issue of posglacial land upheaval and its consequencies for the development of the Baltic Sea. Special emphasis in the book is put on the importance of the geological results for plant geography and archaeology. The two botanists Gunnar Andersson and Rutger Sernander were active in this borderland between botany and geology. As scientists they represented very different mentalities and they soon became enemies. Andersson remained sceptical of the postglacial climate scheme developed by Blytt and Sernander, which he considered founded on too few data. A major scientific schism developed which culminated at the International Geological Congress in Stockholm in 1910. Nordlund is probably right in his view that the interdisciplinary work in the late 19th century relating to historical plant geography and geological development had an impoartant impact on early ecology and its formation as a science.

Landscapes bear witness on past and present natural and societal processes on many different temporal and spatial scales. Major changes of the physical landscape are related to land-forming events, usually followed by continuous processes like weathering, soil formation and erosion. Observed, short-term changes in the physical environment might therefore be adjustments to past events, or the passing of thresholds, rather than reflecting present social and environmental processes.

The different perspectives will be discussed with examples from two Tanzanian villages. In the first example we show how a combination of geological observations and later spatial information from maps and satellite data, field observations, information from villagers and archive studies has increased the observation period and made it possible to map, analyze and explain the natural and human influences on the distribution pattern of miombo woodland in Tanzania and to relate present landscapes to natural events and human decisions in the past, still making their footprints on the present day environment.

This village forms a pocket of apparently sustainable landuse amidst a matrix of more or less degraded land. Another such pocket is found in the Mbulu highlands in northern Tanzania, where it has been explained as a result of intensification of agriculture. In our case we see rather a gradual expansion of the area under shifting cultivation in an area where land is not limiting.

A historical explanation for this development is the fact that this village was little involved in the colonial economy and the villagization program during the 1970s (the “Operation”). Therefore, the population has remained comparatively homogenous and there is continuity in governance. As also population growth has been moderate, its population has been able to continue its traditional landuse in a sustainable way. Today, however, the situation is rapidly changing. Strong economic interests from outside tend to marginalize the influence the villagers have on their own forest resources. External forces are now more important than the internal resource use.

With the concept “simple reproduction squeeze” Henry Bernstein pointed out declining terms of trade for agricultural products as one driving force of agricultural change, requiring constantly increasing production to maintain the income. In most of Africa there is now a negative spiral of land degradation and poverty, and it seems unlikely that industrialisation or the service sector will grow sufficiently to provide livelihoods for the rising numbers of people who no longer can find a livelihood in the traditional agricultural sector. Hence, rural economies must develop and diversify its use of local resources. Our second example is a village where local initiatives could possibly form a basis for an escape from Bernstein’s squeeze. It is important to study closely how such initiatives could develop within a framework of sustained environment and biodiversity. Although alien words like “sustainability”, “development” and “biodiversity” are unlikely to be well understood in the village, they are nevertheless likely to be discussed locally in people’s attempts to escape from the “squeeze”. Therefore, as scientists we need a better knowledge of people’s motives for acting the way they do and of their perceptions of development and sustainability, i.e. an understanding of the local development discourse.

Tree vegetation and size structure was sampled in a miombo woodland area in E Tanzania and related to environmental factors, particularly soil and disturbance history. A total of 86 tree species was found. Four plant communities were distinguished through multivariate classification. Community 1 was dominated by Brachystegia boehmii, Brachystegia bussei and Julbernardia globiflora, and community 2 by B. boehmii and Brachystegia spiciformis. Community 1 was found on grey, eroded soil and community 2 on red, residual soil, a fact that opens up possibilities to use soil signals of satellite data for vegetation mapping. Community 3 is heavily disturbed miombo woodland near villages and community 4 was found on more clayey soil where miombo woodland is not expected. At our 42 sampled sites, density ranged from 74 to 1041 individuals ha⁻¹ and basal area from 3.9 to 16.7 m² ha⁻¹. Regeneration is generally good but large sized trees are less prominent in communities 3 and 4 due to harvesting. With reduced disturbance miombo species may rapidly resume dominance in community 3. A higher than expected representation by the size class 30–40 (−50) cm dbh in community 2 is probably related to disturbance history. Prevalence of certain species (Pseudolachnostylis maprouneifolia, Pterocarpus angolensis and Diplorhynchos condylocarpon) may be related to frequent fires. Selective logging will soon cause extinction of Dalbergia melanoxylon, whereas Pterocarpus angolensis still has good regeneration, possibly because individuals below logging size have a good seed set. A way to get an easy overview of size classes in all species in an area using PCA is discussed.

In the past, arable fields were established locally on the alvar on Öland. Several persisted until the present time, but some of them were abandoned shorter or longer ago. We found a series of arable fields forming a chronosequence: still cultivated, ca. 20 years abandoned, ca. 50 years abandoned, and never cultivated. Species of man-influenced habitats gradually disappeared from the former arable fields, but a few persisted after 50 years. A group of alvar species had re-established after 20 years, but others did not re-establish even after 50 years of abandonment, although they are present in the local species pool. We found no evidence of dispersal as a constraint for re-establishment.

Part of the missing sink in the global CO₂ budget has been attributed to the positive effects of CO₂ fertilization and N deposition on carbon sequestration in Northern Hemisphere terrestrial ecosystems. The genus Sphagnum is one of the most important groups of plant species sequestrating carbon in temperate and northern bog ecosystems, because of the low decomposability of the dead material it produces. The effects of raised CO₂ and increased atmospheric N deposition on growth of Sphagnum and other plants were studied in bogs at four sites across Western Europe. Contrary to expectations, elevated CO₂ did not significantly affect Sphagnum biomass growth. Increased N deposition reduced Sphagnum mass growth, because it increased the cover of vascular plants and the tall moss Polytrichum strictum. Such changes in plant species composition may decrease carbon sequestration in Sphagnum-dominated bog ecosystems.