A large proportion of European biodiversity today depends on habitat provided by low‐intensity farming practices, yet this resource is declining as European agriculture intensifies. Within the European Union, particularly the central and eastern new member states have retained relatively large areas of species‐rich farmland, but despite increased investment in nature conservation here in recent years, farmland biodiversity trends appear to be worsening. Although the high biodiversity value of Central and Eastern European farmland has long been reported, the amount of research in the international literature focused on farmland biodiversity in this region remains comparatively tiny, and measures within the EU Common Agricultural Policy are relatively poorly adapted to support it. In this opinion study, we argue that, 10 years after the accession of the first eastern EU new member states, the continued under‐representation of the low‐intensity farmland in Central and Eastern Europe in the international literature and EU policy is impeding the development of sound, evidence‐based conservation interventions. The biodiversity benefits for Europe of existing low‐intensity farmland, particularly in the central and eastern states, should be harnessed before they are lost. Instead of waiting for species‐rich farmland to further decline, targeted research and monitoring to create locally appropriate conservation strategies for these habitats is needed now.

Summary: 1. Agricultural intensification, at field and landscape scales, has caused a decrease in weed richness and changes in species composition. In order to prevent this loss of diversity and develop efficient management regimes, it is important to understand how both aspects of intensification affect plant diversity and the way in which they interact. 2. This study assessed plant diversity at the centre, edges and boundaries of 29 organic and 29 conventional cereal fields distributed in 15 agrarian localities of the NE Iberian Peninsula. We focused on the composition of plant assemblages and on the specific richness at the field level, which was calculated for the whole set of species and for that of characteristic arable weeds. The percentage of arable land together with human settlements was used as a surrogate for landscape complexity and the amount of nitrogen inputs for land‐use intensity. 3. Our results show that both scales of agricultural intensification have a similar negative effect on the total plant species and characteristic arable weed richness, and they also affect plant assemblages. Furthermore, we found no strong interaction between landscape and land‐use intensity for explaining total plant richness. 4. The relative importance of farming intensity and landscape varies depending on the location within the field, which can be attributed to differences in the agricultural impact and limited seed dispersal from adjacent habitats. Management is the main factor in explaining differences among field centres, whereas changes at boundaries are mainly due to landscape characteristics, and at edges both factors are relevant. 5. Synthesis and applications. To preserve agricultural plant diversity it is equally important to prevent agricultural intensification at field and landscape scales. Policies enhancing low‐intensity management techniques, such as organic farming, are the main way to promote diversity inside the fields and will be equally beneficial in simple and complex landscapes for total plant species richness. To maintain diversity within agricultural areas, it is also important to reduce farming intensity at the edges, which would favour characteristic arable weeds and margins’ overall plant diversity.

Summary: When a plant species is introduced into a new range, it may differentiate genetically from the original populations in the home range. This genetic differentiation may influence the extent to which the invasion of the new range is successful. We tested this hypothesis by examining Senecio pterophorus, a South African shrub that was introduced into NE Spain about 40 years ago. We predicted that in the introduced range invasive populations would perform better and show greater plasticity than native populations. Individuals of S. pterophorus from four Spanish (invasive) and four South African (native) populations were grown in Catalonia, Spain, in a common garden in which disturbance and water availability were manipulated. Fitness traits and several ecophysiological parameters were measured. The invasive populations of S. pterophorus survived better throughout the summer drought in a disturbed (unvegetated) environment than native South African populations. This success may be attributable to the lower specific leaf area (SLA) and better water content regulation of the invasive populations in this treatment. Invasive populations displayed up to three times higher relative growth rate than native populations under conditions of disturbance and non‐limiting water availability. The reproductive performance of the invasive populations was higher in all treatments except under the most stressful conditions (i.e. in non‐watered undisturbed plots), where no plant from either population flowered. The results for leaf parameters and chlorophyll fluorescence measurements suggested that the greater fitness of the invasive populations could be attributed to more favourable ecophysiological responses. Synthesis. Spanish invasive populations of S. pterophorus performed better in the presence of high levels of disturbance, and displayed higher plasticity of fitness traits in response to resource availability than native South African populations. Our results suggest that genetic differentiation from source populations associated with founding may play a role in invasion success.