Discussion: Confronting ELIA results with Margalef’s
hypothesis
We have checked Margalef’s
hypothesis on the capacity to host high biodiversity in cultural
landscape mosaics resulting from a complex distribution of external
energy flows of farming, by testing the links of the spatial
energy-information structure with the species richness of butterflies
and bird populations observed in the Barcelona Metropolitan Region
(31 ,37 ,40 ). The results confirm that
agroecosystems are key to halt the serious decline of butterfly
populations in Europe (41 ), which can also be taken as proxy of
many other current biodiversity threats (42 ). The importance of
the energy landscape redistribution (I ) carried out by farmers is
coincident with recent research highlighting that the worrying decline
of common birds’ populations in European cultural landscapes is related
to the abandonment of long land use patterns of human-made
agroecosystems (43 ).
The Energy-Landscape Integrated Analysis has demonstrated to be an
efficient predictor of butterfly and bird locations in the
human-transformed landscapes studied. Indeed, ELIA can better
predict these biodiversity locations than landscape composition or
configuration metrics taken alone. Farmers’ uneven spatial distribution
of the biomass energy flows (I ) of agroecosystems appears to be
the key factor to explain butterfly observations and species richness,
but also breeding and wintering species richness. This is an important
outcome that points out to the role of farmers’ knowledge in designing
the ecological functionality of biocultural landscapes through a subtle
human-nature relationship (40 ). It confirms that the interplay
between the energy reinvested (E ) and redistributed (I ) by
farmers affects the landscape functional structure (L ) and its
associated biodiversity through the harnessing of biomass flows that
loop within these human-transformed landscapes.
The analytical advances and positive results obtained mean that the
usual methodology of energy flow analysis of social metabolism and the
classical landscape ecology metrics need to be adapted, enlarged and
integrated to account for the complex cyclical character of human-driven
land use changes in cultural landscapes. Traditional farm systems with a
solar-based metabolism tended to organise their land usages according to
different gradients of spatiotemporal intensity, keeping an integrated
management of different land
patches because their whole subsistence depended on the endurance of
that landscape functional structure (40 ). In order to offset
the energy lost in the inefficient human exploitation of animal
bioconversion, on which they had to rely to obtain traction and manure,
past organic farmers kept livestock breeding carefully integrated with
cropland, pastureland and forestland (44 ).
While the traditional organic farm management scheme of closing energy
cycles within complex agroecosystems led to landscape mosaics which
allow a land sharing strategy for biological conservation
(45 ), the agroindustrial farm systems that rely on external
flows of inputs coming from underground fossil fuels have enabled
society to overcome the age-old energy dependency on bioconverters
(46 ). As a result, integrated land-use management was no longer
necessary, and overcoming that former necessity led to the loss of its
agroecological virtues. Nowadays biodiversity conservation in land
matrices mostly occupied by cultural landscapes cannot be guaranteed
only through the protection of natural areas (land sparing ) in
exchange for promoting an ever more intensive industrial agriculture. It
requires, instead, an improvement of the ecological connectivity and
functionality of the whole land matrix by recovering and enhancing
agroecology landscape mosaics (land sharing ). This also means to
start scaling up the agroecosystems’ functioning at the landscape level
to cope with and offset the land cost of sustainability (47 ).
Therefore, the integration between social metabolism and landscape
ecology approaches is crucial for further developments of sustainable
land-use planning.